* * *

* * *

THE sky was a deep, serene blue, patched with slow-drifting, fleecy clouds. Even the roar of the Spad's engine had a lazy, droning note. Captain Philip Strange leaned back in the cockpit, his thoughts on the sunny Italian villa he had left behind. Those weeks of convalescence had been a welcome interlude. One espionage mission after another had brought his taut nerves to the breaking-point, but now that raw-edged strain was gone.

Naples had given him back his soul. Only once before had he known such peace and relief. That had been years ago, when he had run away from a tyrannical uncle—a greedy old man who had put him on the stage as a boy prodigy, exploiting his uncanny memory and his gifts for lightning calculation. Since then he had roamed the world, learned a dozen languages, and discovered odd secrets in a hundred parts of the globe. But the war had ended that, and under an assumed name he had enlisted at Kelly Field.

The rest was a flood of memory . . . Wings . . . France ... a few weeks at the Front, until G.H.Q. had learned his identity. They had made him a G-2 ace and success against the Boche had made him a hunted man with a price upon his head.

He was living on borrowed time, but suddenly, as he looked at the blue-black guns on his cowl, he was glad to be going back. His mind was rested, and he felt an eagerness stirring in his veins. The theater of war lay not far ahead, and he knew that already a role awaited him on that grim and dangerous stage. With a rekindling of interest, he thought over the two messages which Colonel Jordan had sent him. The first had been delivered at Naples, through Italian Intelligence. It ran:

Strange laughed to himself. He could almost see the irate face of the G-2 chief as he wrote the words. The message still made no sense; it looked like something one of the Jay twins might have written. And the second message, handed to him by an Intelligence officer when he had refueled at Lyon, seemed to have no connection. He recalled the words precisely:

Strange looked over the side of the cockpit. The Molaine was already in sight—a wide, muddy stream which meandered along through the foothills of the Vosges. Beyond Sautney, he remembered, it curved eastward through the German lines and then back again into France. He could see Sautney about five miles ahead, a cluster of little white houses, like a toy town there in the late afternoon sun.

HE frowned thoughtfully as the Spad droned down in a glide. The affair must be of unusual importance, to bring Andre there. The explosive little major was chief of French air intelligence, and from long association with him Strange knew he never left his beloved Paris unless the reason was urgent.

At a thousand feet, he banked the Spad into a fast spiral. A glance below showed him the house which Jordan had mentioned. It stood alone, a small, shabby building with a boat-landing in front of it and a roadway stretching behind it and toward the village. He was about to straighten out for his approach to the clearing, when he saw a French Breguet come slanting down from the West. Evidently Andre was just arriving for their meeting at Sautney.

The man in the front cockpit made a curious signal with his right hand. Strange started to answer, then his eyes narrowed. It was a close imitation of the little major's usual signal—but the man was not Andre.

Without any sign of having guessed the truth, he raised his hand in answer. In the next instant, he jerked at the stick and sent the Spad into a tight climbing turn. A fierce burst famed after him from the Breguet's cowl gun. He kicked over at the top of the zoom and dived. The gunner was frantically whirling his tourelle. Yellowish lines from the Spad's Vicker probed through the two-seater's tail and on to the rear pit. The gunner threw himself aside, and the smoking streaks missed him by inches.

Before Strange could correct his aim he was forced to plunge aside to avoid a collision. A blast from the Breguet's rear guns tore through his left wing. He booted the rudder, slipped clear, then came up under the other ship. The pilot whipped into a vertical bank, to give the gunner another chance. Strange raked the bottom of the tilted plane, and the spouting Lewises darkened. He saw the gunner's dead face as he chandelled past the Breguet. The man's eyes were closed, as though he had tried to shut out that blazing doom.

The two-seater corkscrewed away to the right as Strange opened fire again. With surprising skill, the pilot jerked the heavy plane up and around in a split. His clattering gun made a crooked black track over the Spad's wingtip. As the phosphorous streaks feathered off into space, Strange renversed. The tail of the Breguet came into his sights. He tripped the Vickers, lifted their red jets of lightning over the two-seater's rudder. Fabric flew from the spy-ship's tail as the bullets ate their way forward. The pilot hurled his ship into a desperate bank, but Strange grimly followed through.

That deadly dotted path was almost to the front pit when a flitting shadow dropped from the heavens. The Spad's windscreen went to pieces before Strange's face, and two furious bursts ripped his instrument board into ruins. He kicked into a half-roll. A Nieuport with French cocardes plunged by and twisted back. Strange sprang up in his seat as he saw the swarthy face and mustaches of the pilot. It was Andre!

At his hasty signal, the little major's mouth opened in astonishment. The Nieuport slid in parallel, then Andre raised both hands in a typical Gallic gesture of bewilderment. The Nieuport's nose dropped. Andre grabbed at the stick just as the Breguet whipped down at him, and the single-seater wormed out from under the other plane with the agility of an eel. In spite of the tense situation, Strange grinned as he saw that maneuver. It was, like the gesture, typically Andre.

But his grin faded in the next second, for with a startling renversement the Breguet pilot threw his ship between the two fighters. Strange had clamped his trips as the other man whirled, but he jerked his fingers away as he saw Andre's Nieuport beyond. The Breguet was thundering straight at him, its single gun pounding fiercely. He slammed the stick to his belt, and the Spad drilled up straight in front of the roaring two-seater. There was a taut moment when he thought his swift calculation had led him into a trap. The Breguet's prop seemed about to crash his flipper planes.

Then the Spad was free, though the fuselage was a bullet-gouged wreck. He pulled on over in a hard, fast loop. His guess was right—the Breguet had whirled back at Andre. The Nieuport was scuttling around toward the two-seater's tail, with the Breguet's tracers almost scorching its rudder. Strange coolly centered his guns. His Vickers belts leaped from their cans, and over the throbbing guns he saw the pilot fall.

With a snap, the Breguet nosed down and pitched into the muddy river. The dull sound of the crash reached Strange's ears above the bellow of his engine. He watched a geyser of dirty water shower back on the crumpled ship, then he slid his fingers away from the trips and looked around at Andre.

The little Frenchman vigorously signaled his thanks and pointed toward Sautney. Strange gazed down for an instant, waggled the Spad's wings and dropped in a fast sideslip. From the ripples on the water he could see the wind direction. He circled above the isolated house on the shore, then carefully glided down to the tree-bordered lane beyond it. Fishtailing to lose speed, he put the fighter down. It rolled to a stop in a cloud of dust, a quarter-mile from the house. As the dust settled, he heard the whine of the Nieuport, then Andre brought his swaying ship down. It hit, bounced, and finally came to a stop with one wing almost against the trunk of a tree.

STRANGE had switched off his engine and swung his long legs to the ground. The dust from the other ship settled, and the wiry Surete major bounced from his cockpit.

"Sacre bleu!" he sputtered. "It is a wonder you did not pick the roof of the house to land on."

"I thought I'd get down before you took another pot-shot at me," said Strange, drily.

Andre grimaced.

"Mon ami, I beg a thousand pardons. I received a wireless message supposed to be from that human bull-dog chief of yours saying he and you were flying to Sautney in a Breguet. I thought you were being attacked by a Hun in a captured Spad. It is a good thing my aim was not better, n'est-ce pas?"

"No argument there," said Strange. "For a second I thought France had declared me an undesirable alien. But we'd better go back to the house and look into this other matter. From the attempt they made to get rid of us, it must be something important."

"I hope so," retorted Andre, twisting his ruffled mustaches back into shape. "Especially when I follow you like a lunatic and almost break my neck landing on this cowpath."

They started along the lane.

"I know nothing about this Meade case," Strange told the little major. "Perhaps you know the details?"

Andre shook his head.

"Only what your colonel phoned us that he was relaying to you. Meade was working on the same thing which has driven us all half mad. But yon were in Paris before '14—you may recall our trouble with Monsieur le Diable?"

"You mean that phantom thief who mocked the police? Yes, I remember—he first broke into print when he stole the guillotine after it had been set up for an execution at Bourg."

Andre made a wry face.

"That was only half of it. He also stole the executioner, though we managed to keep that quiet."

"An original rascal," Strange chuckled.

"Too much so," lamented Andre. "He was like the lightning—one never knew where he would strike, or what insane thing he would do next. One night, he robs some fat old miser and leaves a dozen clues. We rush along the trail, and then—Pardieu! We find ourselves in a cemetery, and there is a bottle of champagne and one of his impudent notes: 'Something to refresh you, messieurs, after your arduous chase.'"

"Good wine?" inquired Strange.

"How am I to know?" growled Andre. "The Prefect drank it—after it had been tested for poison."

"And you never had an inkling as to who he was?"

"Inkling? Nom d'un nom! We find fingerprints—and they turn out to belong to me, Andre, and I have one fine time of it proving I am not this M. Devil. We hear he is at the Gare du Nord. We rush there, and while we search the Brussels Express he makes off with the engine and escapes. The engine is found, with the driver and the stoker bound, on a siding near La ChapeIIe. The men say they were overcome by an old man with a white beard, who had a prodigious strength. Our miser tells us that Monsieur Ie Diable is young and thin and redheaded, and another says he is tall and dark as an Arab. The Surete despairs—we expect at any moment to hear he has made off with the Eiffel Towel or the Arc de Triomphe. Then the war comes and we hear no more of him—that is, until ten days ago."

"So that's why Jordan was afraid of having his pants stolen," observed Strange.

"Oui, but it is no laughing matter, Strange. This crazy thief has upset the whole war. He makes fools of us and Germany both, and for no reason. One morning a turnkey finds three German colonels locked in a cell at Vincennes, and they swear they went to sleep in their quarters at Thionville and have no idea how they got across the lines and into our prison. Then we find a card saying, 'With the compliments of Monsieur Ie Diable.' Next day this monster makes off with three of our colonels—and we learn they have turned up in a Boche prison."

Strange laughed outright. Andre looked at him sourly.

"You will not think it so funny, mon ami, when your superiors have you up for not finding this M. Devil.

They are all quaking in their boots, and they take it out on the Intelligence. Me, I am about to be shot or reduced to a private. But i have told you only a hint of it. M. Ie Diable. does not confine himself to colonels. He steals a civilian official in Barle-duc after dinner, and a drunken sous-officier in Nancy before midnight. Between then and two o'clock he makes off with the middle section of a pontoon bridge across the Mouse River, and no one has found it yet. He steals a portable barracks set up one night in the Bois de Varine. It is to be a secret headquarters for a division, and when the officers come in the morning there is not a sign of the building —only a stake with one of M. Devil's cards on it. Next day the building is found set up forty kilometers away, in the middle of another woods. Within is discovered an escadrille pilot who had been a German prisoner for six months. He was in irons, and he had the same story of going to sleep in Germany and waking up in France."

"Almost incredible," Strange muttered.

"If you do not believe me," Andre bristled, "I can show you the evidence."

"I said 'almost incredible,'" Strange reminded him.

"At first thought, there seems no possible motive, but there must be something powerful back of it."

"But he strikes at the Boche, too," objected Andre, "and there is no military value to anything he steals from us—not even our three colonels. In fact, M. Ie Diable did us a favor there," he added with a chuckle.

Strange looked at him thoughtfully as they strode along the hot, dusty road.

"There's a curious pattern to all this, Andre. If only we could see the main thread—but perhaps we'll learn something here to help us."

THEY were almost to the fisherman's house, and as they turned in from the lane Strange saw a stooped and weazened figure in patched corduroy waiting for them at the gate. There was something pathetic in the look of relief whieh crossed the old man's face as they approached.

"Mon pere," said Andre, "I am of the military. You are Georges Lamotte?"

"Oui, oui," quavered the old man. His rheumy eyes looked pleadingly from Andre to Strange. "Please, messieurs, take that awful one out of my house, messieurs. I begged the gendarme not to put him in there—"

"Where is the gendarme now?" Strange interrupted.

"He went away on his motor cycle, m'sieu, when the fight in the air began. He was very much afraid when he saw the areoplanes."

Andre and Strange looked quickly at each other.

"Show us the body," the brisk little major ordered.

The old fisherman cowered.

"Non, non—do not make me look at it again. Even now I will be afraid to sleep there after—"

"Vite!" snapped Andre. "A dead man can't hurt you."

Whimpering, the old man led them toward the house. They went up onto a rickety porch at the left, beyond which steps led down to the boat landing, where a weatherbeaten dory moved sluggishly with the current. Lamotte opened a door and limped inside. There were only two rooms, a kitchen at the front and a bedroom at the rear. The old man shuffled to the bedroom door, then stopped with a gasp.

"The dead man! He was on the floor—and now he is in my chair!"

Andre was a step in front of Strange. He sprang past the old fisherman, then Strange saw his swarthy face turn pale.

"Nom de Dieu!" he whispered. "What terrible thing is this?"

Strange halted in the doorway, transfixed at the sight before him. The descending sun, slanting through a western window, made a bright rectangle, and framed in that ruddy glare was a shining black corpse!

It had been propped up in a rocking-chair, and at first glance it had the appearance of a gruesome statue painted black. But the dreadful angle of the head, and the limpness of the dangling arms told the grim secret. Under that horrible shiny blackness was a human body.

For a moment longer, Strange stood gazing down at the dead man. From head to foot, face, uniform and boots, he was that same glistening black—even to his thick, closed eyelids and the matted hair which showed under a tight-strapped helmet. His lips and nostrils were sealed by the queer dark substance, but through the layer which blurred his features Strange caught something familiar.

"Andre!" he said swiftly. "Come over on this side— look at his face."

The Surete major appeared to awake from a daze. He came around past the trembling fisherman, stared at the dead man’s profile.

"Pardieu!" he said in amazement. "It’s Franz Schermann – the leading ace of Germany’s 55^th Staffel!"

Strange slowly nodded. He was bending closer over the blackened figure when Andre gave another exclamation and snatched up something from the floor. It was a small card which had apparently fallen from one arm of the rocker.

Andre's dark eyes almost popped from their sockets as he stared at it. With a groan, he handed it to Strange. At the top was embossed a tiny red devil, a mocking grin on its face. Underneath, several words had been printed in pencil: "A gift to my old friend Andre, from Monsieur Ie Diable."

Strange read the words without a change of expression, but as he looked down at the dead German ace he shuddered. For that black figure in the chair seemed in truth a gift from the Devil.

ANDRE suddenly turned to the old fisherman. "This gendarme—describe him—where did he come from?"

"He was a big man, and fierce," faltered Lamotte. "I am not sure, m'sieu, where he was from. He was here when I came back from the village, after I found the— the body. Jacques, the storekeeper, had telephoned to Lemieres for police, so he must have come from there. He was very angry when he saw Jacques and the others who came back with me, and he told them to go away or he would arrest them. Then he made me get a plank and help him carry the dead man on it, and after that he told me to go outside. When he heard the first aeroplane, he ran out and was very frightened. When the others came and fought he jumped onto his motorcycle and rode away."

"In which direction?" snapped Andre.

"To the west, m'sieu Ie officier, where the lane goes through the woods. Can I go now? I have told you everything."

"You have not described the gendarme," Andre said impatiently. "Was he young or old, fair or dark, smooth-faced or bearded?"

Lamotte wrinkled his forehead.

"I think, m'sieu, he was nearing forty, and he was very red-faced because he was angry. There was no hair on his face, that I am sure. I did not look much at him because he made me afraid."

Strange turned from a close inspection of the corpse.

"The gendarme used gloves when he washed the mud from the body, didn't he?"

The old man looked astonished.

"Oui, but how did you know about—"

"What was his reason?" Strange cut him short.

"I suppose to keep his hands clean," Lamotte said helplessly. "When I found the body, it was floating not far offshore. I hooked it with my boat-hook and towed it ashore. The bank is quite muddy—" the old man's words trailed off as his eyes went toward the dead man. He sprang back with a cry, then fled wildly from the house.

Strange and Andre wheeled to see the cause for his fright. Both of them took a step backward, for the chair with the corpse was rocking.

"Name of a saint!" muttered Andre. "In another moment I shall run out of here also."

"It must have been a little puff of wind," Strange answered. He stared at the blackened figure. "I'd give a lot to know why our gendarme propped him up in that chair."

Andre wiped his moist face.

"Let's go outside, mon ami. The room is stifling, and the sight of that wretched Boche is making me a little sick."

"Wait," said Strange. "I'd like to find what this black stuff is."

He folded his handkerchief, rubbed at the dead man's cheek. The dark substance was warm from the sun, and its firm, waxy surface softened a little under his pressure, but only a smudge came off on the cloth. He rubbed again, and this time saw he had taken off the shiny outer layer. He looked up at Andre.

"Did you ever see a vat of the material from which phonograph records are made? The stuff is hot and plastic, and it hardens like this."

Andre started.

"You don't mean this Boche has been dipped into such a vat?"

"He might have fallen into one, though it seems—"

Strange held the smudged handkerchief to his nose.

"No, it isn't that, either. I know the odor of that record material—it's a mineral composition, sometimes with resin and shellac in it. This odor is entirely different, and yet it's vaguely familiar. I'd like to analyze some of the stuff in a laboratory."

"I can arrange to have the body taken to your Second Corps Headquarters," said Andre. "But now, let us get out of this place."

HE moved to the door, halted with a jerk. The chair was rocking again.

"It's a loose board—you stepped on it just now," said Strange. Then he stared at the little major. "Lamotte must have known about that board. I believe he rocked the chair purposely so he'd have an excuse to duck out of here."

"Eh bien, I can hardly blame him," said Andre, but Strange hurriedly made for the porch.

"Lamotte lied to us," he said in a low tone. "He knew the chair was placed exactly in the right spot to make it rock. That means he was in there when it was done— and he may have done it himself."

They went out onto the porch. At first glance, there was no sign of the old fisherman, then a sprawled form halfway under the boat-landing steps caught Strange's eye. He ran down, with Andre after him, and turned the man over. It was Lamotte. He had been dealt a fierce blow on the head, but he was alive.

"Watch the front of the house," Strange said to Andre, "while I try to bring the old man around. Whoever did this can't be far away."

He carried the unconscious fisherman out into the sun. As he laid him down Lamotte's muddy shoes fell off. A startled look came into his face as he eyed the old fisherman's clothes. He whirled to shout to Andre, but the cry died on his lips, for a stream of black smoke was pouring from the opened bedroom window.

As he ran toward the house Andre dashed around from in front. The little major's breathless exclamation was lost as red flame suddenly burst from the billowing smoke. The side of the house instantly blazed, and smoke began to pour from the front and rear windows. By the time Strange and Andre reached the other side almost the whole building was in flames.

"Stay here—I'll watch the side toward the woods," Strange rapped out. "I don't think anyone's in there, but we'll make certain."

He rushed back to the spot where he had left Lamotte, and moved the old man farther from the blaze. With growing amazement he watched the burning house. The flames were a veritable rainbow of vivid colors, giving a dreadful beauty to the inferno. The intense heat forced him to move Lamotte still farther away. The fire leaped to the boat-landing, to the dory, to the nearest trees. Then, abruptly, the rainbow flames died, and a thin white smoke took their place. With astonishment, he saw that only a layer of ashes remained where the house had been. Andre ran around to where he stood.

"Mon Dieu!" he said hoarsely. "What kind of hell-fire was that? The house burned completely in less than a minute."

Strange gazed silently at the smoking ashes. He could see nothing of the corpse.

"It must have been a new kind of incendiary bomb," Andre went on in a dazed voice. "The man who struck down Lamotte must have thrown the bomb through another window while we were coming out, and then escaped into the woods."

Strange shook his head, went to the river bank and took out his handkerchief. He wadded it tightly and rolled it in mud until it was well covered. Andre looked at him with his mouth wide open.

"Have you lost your senses? The house burns— We lose the black corpse—and you stop to make mud balls!"

Strange glanced along the lane. Several villagers were running toward the spot, evidently having seen the brief blaze.

"Stay with Lamotte until they get here," he said to Andre. "Don't explain anything but barest essentials. I'll get our engines going."

He started on, paused and took out his wallet.

"Here," he said, pressing some bills into Andre's hand, "put this money in the old man's pocket and tell the villagers his house will be rebuilt in a few days."

"But, mon ami, why should you do this?" exclaimed Andre.

"Because if I hadn't been so stupid," Strange retorted, "his house would still be standing."

He hurried on before the puzzled Frenchman could speak. As he passed the ruins of the building he looked toward the space where the rocking-chair had been. Among the gray-white ashes were streaks of rainbow colors. The faint outline of that queer, colored spot was like the shape of a human body.

* * * *

IT was nearly sundown when the two ships nosed down toward the Second Corps field outside of Chaloncourt, though they had flown at full throttle since the moment of taking off from the lane. Strange looked across at Andre, then for the hundredth time searched the sky. There was no sign of planes, German or Allied. He drew a breath of relief, for he had expected a different reception.

He glanced down at the Corps drome, six thousand feet below, then sat up quickly. Ships were darting across the field, one after another, in hasty take-offs. He flung another look about the sky, raised one hand to his eyes to peer through his fingers at the sun. Vague, flitting shapes suddenly became visible against that blazing red disk. He threw a frantic signal to Andre and rammed the throttle open.

The vague shapes became in a flash the wings of hurtling Fokkers. Consternation swept over Strange. There were at least two dozen of the coffin-nosed fighters!

It was too late to dive for the field, and to fight meant a swift death. With stick hard back, he zoomed for the clouds. Andre's Nieuport was already streaking up for their protection. As the three leading Germans shot up to intercept the fleeing ships, Strange hammered a burst across the cowl of the first D-7, and the Boche kicked into a skid. Andre plunged at the middle Fokker, and for a taut instant Strange thought they would crash head-on.

But the Nieuport zoomed at the last second, and a riddled German fell over the Fokker's stick. Five more D-7's were drilling up at furious speed, Spandaus blazing madly. Tracers from three directions smoked through Strange's wings. The right-hand aileron jerked under a hail of lead, and fabric streamed back in ragged strips. Strange pitched the Spad between two Germans, dived under a third. The dive hurled him straight at a fourth D-7. He pumped a blast into the Fokker's nose, and the German's belching Spandaus were lost in a gust of flame from the stricken engine.

Andre was almost in the clouds, with three Boche climbing fiercely after him. Strange pulled up behind the flamer, so close that he felt the heat as he zoomed. A plume of greasy smoke had billowed back over the Fokker. He jerked the Spad up into it, and the murderous pound of bullets for the moment slackened.

It was but a second, that reprieve, but it gave him a chance for life. He twisted sharply in his climb, and the Spad came out at right-angles to its former position. Five or six Germans shot by, banking hastily to bring him under their guns. But the clouds were hardly two hundred feet above him now, and only a single D-7 was between him and safety.

The lone Boche whipped around sharply, and Strange saw the insignia on the side of his fuselage. It was a ship of the 65th Staffel—the squadron to which Schermann had belonged. The Spandaus beat out a venomous rat-a-tat as the German crouched behind the guns. Bullets tore through an outer strut of the Spad, and the slug-riddled fighter trembled. With a prayer that the cracked strut would hold, Strange banked tightly. Two more Fokkers were charging in, but he held to the turn until his almost empty guns raked over the other ship's tail.

Tracers suddenly probed from the edge of the clouds, and Andre dropped squarely on the first of the two charging Germans. The D-7 went over onto its nose, its tail shot clear off. The second one hurriedly twisted aside, and Andre pulled back in a wild zoom which scattered two more Fokkers. Strange saw the first filmy haze of a cloud spread over the Spad. With Spandaus blazing from every direction, he pulled on up into the shrouding mists. Turning slowly, he leveled out and flew blindly through the darkening cloud.

NOT until then did he realize that there was blood on his face. The compass had been shot to pieces, and flying glass had cut his jaw. There was a numb spot along his right thigh, and for a moment he thought he had been shot. He looked down and saw where his Army .45 had been hammered against his leg by the impact of a bullet The slug had hit squarely on the heavy gun, and the impact had driven the barrel against his leg.

The Spad was a flying junk-heap, and from the uneven pound .of the Hisso he knew it would not be flying much longer. He eased back the throttle, made a quick estimate. The scene at the moment he had entered the cloud was like a photograph etched on his memory, even to the streets of Chaloncourt. The Corps field had been about three miles east, and there had been more than a dozen ships in the air, climbing to engage the Fokkers. He had turned east at that last second. He kept the Spad flying as straight as possible for several minutes, then cautiously nosed down.

He came out a trifle north of where he had expected to emerge, but at his calculated distance of five miles eastward. There was no one near him, and he could see that the Germans were giving way under an attack by two Allied squadrons. He started down in a careful glide, watching the half-broken strut. At three thousand feet he saw Andre's Nieuport poke its nose warily from the clouds, like a mouse coming out of a hole. The Frenchman spiraled down beside the Spad, and together they made for the Corps field. They were just below two thousand feet when from somewhere beyond Chaloncourt a rocket shot up and burst into three blue stars.

The German Jagdstaffel instantly broke from the fight and raced away to the east, followed by some of the Allied planes. As Strange leveled off to land, part of a Spad squadron swept down toward the field. He saw two ships flying separately. They dived for the drome, zoomed recklessly across the hangars, and looped at three hundred feet before his ship had even stopped rolling. Andre was just taxiing up beside him on the line when the two Spads landed. He shoved up his goggles and looked at the numbers on the Spads as they rumbled closer. A brief amusement came into his eyes as he saw the pilots. If Tom and Noisy Jay had ever taken the war seriously, they had managed to conceal that fact. They were the same wisecracking twins he had seen do ventriloquism and magic acts in vaudeville before the war. Service with G-2 and pompous Brass Hats had failed to change them.

Noisy was the first to recognize him as he climbed out of the bullet-torn Spad. He leaped from his cockpit with a joyful yelp. •

"Well, I'll be a flat-footed hoofer! Hey, Tom—look who's here!"

Tom dashed across, a reckless, likable youngster in exact duplicate of Noisy except that his grin was a trifle less impudent.

"Phil!" he said, seizing Strange's hand. "Where did y6u pop from? I thought you were still in Italy, stuffing yourself with spaghetti."

Then both the twins for the first time noticed the condition of Strange's Spad and Andre's Nieuport.

"So you were the birds those Krauts were after," exclaimed Tom. "I wondered who—say, are you hurt?"

Strange shook his head.

"Just a nick. Andre, are you all right?"

The little major climbed gingerly from his plane.

"Oui, except for a case of heart failure," he responded. "I thought at first the whole German Air Force was after us. I have never been a praying man— but I made up for it today."

Noisy whistled as he surveyed the tattered ships.

"Boy, that's what I call a welcome home party. You could use those wings for porous plasters."

An important-looking officer pushed his way through a group of staring mechanics, and Strange recognized Lieutenant Peck, one of the G-2 men stationed at Chaloncourt. Peck saluted briskly.

"Captain Neville," he said, using Strange's customary pseudonym in G.H.Q., "Colonel Jordan would like to see you and Major Andre at once."

Strange nodded, motioned to the Jay twins.

"Better come along, you two—I've a hunch you're going to be needed."

Twenty minutes later, in the privacy of an Intelligence office, Strange finished his hasty explanation to the chunky G-2 colonel. Jordan's bulldog features had taken on a stunned look as he described the mysterious black corpse.

"Good Lord!" he whispered. "Maybe that's what happened to the stolen Allied pilots."

"Stolen pilots?" Strange exclaimed. "Andre didn't tell me about that."

"It began only last night, and the reports have just come in." Jordan looked grimly across his desk at the taller man. "Strange, in twenty hours that fiend has robbed the Allies of as many aces—and he's threatened to take them all!"

STRANGE gazed at him through the smoke of his cigarette. "So they're finally coming out in the open," he muttered.

"Who do you mean by they?'" snapped Jordan.

"The Germans, naturally," said Strange. "You know that no one man could have done all these things. And second, only the Boche could have a strong enough motive."

"But they've been hit as hard as we have," protested Jordan. "The Allied Intelligence Pool has a list of equally crazy stunts which this Monsieur Ie Diable has pulled in Germany. I know they're facts, because our agents have checked up on a lot of them—and we have about twenty-five Boche prisoners who were deposited in various parts of France by that lunatic."

"I'd like to see that list—also the record of things which have happened on our side," said Strange.

"Beeding will be here with the latter record in the next. thirty minutes," returned Jordan. "And Colonel de Souey is going to meet me here with the Pool report. He sent word he had a clue to the identity of Monsieur Ie Diable."

"With no disrespect to my commander," Andre interposed, "I would not expect too much from that clue. Colonel de Soucy always has a clue, but unfortunately it has a habit of leading into empty space."

"I can think of a similar case in G-2," said Strange.

The Jays snickered, and Jordan glared.

"That's a fine way to talk about me, after I let you loaf in Italy all this time."

Strange laughed.

"I didn't mean you, colonel—I was thinking of Lieutenant-Colonel Beeding."

Jordan looked at him suspiciously.

"Well, in that case I," he reddened, cleared his throat. "Can't have such talk about senior officers! Never mind about Beeding, I brought you back to help me. We're launching an offensive at dawn in Sector Three and we'll need every available pilot."

Strange sobered.

"How were those aces abducted, colonel?"

"We don't know," growled Jordan. "They simply disappeared. Three of them—Americans—were on leave in Paris. They didn't show up this morning at their squadron, but their S.C. got a letter with one of those red devil cards and the three pilots' names written on it. We lost seven more aces during the night—two at Barle-duc, and the rest from different squadrons. They were last seen at estaminets or on their way to a binge or something. In each case, one of Monsieur Ie Diable's cards turned up. And it was the same with the French and British pilots who disappeared."

"And the threat to steal all the aces?" queried Strange.

Jordan scowled.

"Somebody left the message on Beeding's desk—he thought it was one of the G.H.Q. orderlies, but we cleared the man. It was signed by this phantom thief and it said he found the company of Allied aces so inspiring he thought he would collect all of them for his personal entertainment. But I've worked out a scheme to fix Mr. Devil. I'm going to create two more ace-trains, and they'll be armored cars and guarded with machine-guns."

Strange squashed out his cigarette.

"I didn't know we had any ace-trains. When did you start that?"

"About a month ago. It was General Thorne's idea; the Boche has been jumping the Richthofen Circus all around and shooting them into a sector tor a day and then into another one twenty-four hours later, upsetting our morale all along the Front. So Thorne made up a squadron of aces and we put them on a train with the coaches painted like hospital cars. The train moves on secret orders by wireless from G.H.Q. and the pilots live on board all the time. Just before dawn, they hop into cars at some railway siding, and rush to the nearest squadron. They take over the squadron's ships and raise hell in that sector for a few hours and then get back on the train and pull the same trick a hundred kilometers away next day."

"Nice set-up for the pilots they leave behind," Strange said dryly.

"It doesn't hurt them," Jordan grunted. "The aces clean up the Boche so that our men have a top hand for a while. And it's thrown a kink into the Richthofen Circus idea."

"Where's that train now?" Strange asked him.

"On its way here from a siding near Base Hospital Two. We've side-tracked it close to different hospitals several times so it would look on the level, and had the pilots driven to the nearest squadron. They're coming here to be ready for the offensive—that's why that extra Spad squadron was flown up here. But forget about that for a minute. This business about the black corpse worries me. If that story spreads, and Allied aces think they're in for the same thing—"

"The most important matter now," Strange interrupted, "is to get this to a chemist."

HE took the mud ball from his flying-coat pocket. It had been somewhat flattened, but the handkerchief did not show through. Colonel Jordan looked at it and turned an angry red.

"See here, Strange, I'm in no mood for jokes!"

"I'm not joking," Strange replied calmly. He explained about the smear on the handkerchief. "It's obvious that the black substance is highly imflammable when exposed to heat. That's why the corpse was propped up in the sun, so spontaneous combustion would set it on fire and burn down the house, destroying all the evidence. An analysis of that smear may give us the key to the whole thing."

"And old Lamotte might have given us a lead," Andre cut in tartly, "if you had not made me hurry off."

"He couldn't have helped us," Strange answered. "He may not even' have seen the gendarme."

Andre's black eyes popped.

"Where is your faultless memory? He described the man and how he ran away when the ships came."

Strange started to reply, but there was a quick knock, and Lieutenant Peck hurried into the room.

"Colonel de Soucy has just arrived by plane, Colonel Jordan," he rattled off briskly. "He asked to see you alone, and he's waiting in the conference room."

Jordan strode out after a word for Strange and the others to remain in the office. Strange turned to Peck.

"Any luck on that check-up I asked you to make about the man who fired the blue rocket?"

Peck swelled importantly.

"I have three men on the case, sir. There are several people in Chaloncourt already under suspicion of espionage activities, and we should soon tag the guilty man with this as a clue."

"H-m-m," said Strange. "You and Beeding, eh?"

"Begging the captain's pardon?" said Peck, nonplussed.

"Let it go," Strange held out the mud ball. "Take this to the chemistry lab. There's a handkerchief inside, and a black smear on the handkerchief. I want the smear analyzed. Tell the chemist not to get it near any heat."

Peck looked disapprovingly at the wad of mud, reluctantly took it up in his dainty fingers. Holding it away from him, he went toward the door. Suddenly a low buzzing sounded, apparently from inside the mud ball. Peck dropped it and leaped back with a yell.

Strange looked at the Jay twins, whose faces showed a blissful innocence.

"It's all right, lieutenant," he said to Peck. "One of these two idiots was just brushing up on his ventriloquism. You have my permission to punch his nose —if you can pick out the right one."

"I should prefer to ignore such persons," Peck replied frigidly. He picked up the mud ball and stalked from the room, a picture of outraged majesty.

"Consider yourselves squelched," Strange said to the Jays, who were now grinning from ear to ear. "And if you can drag your minds down to such unimportant things as the war, do you know anything about this Monsieur Ie Diable?"

"Only what we just heard," said Tom. "We knew something had the Brass Hats running in circles, but Colonel Jordan had us on another job, down at Marseilles. They've kept it pretty well covered up, or we'd have known about it."

Strange turned to Andre.

"I hope your friend de Soucy really has some information this time."

"At least, something has galvanized him into life," said the little major. "It must be of importance, for him to risk his precious neck in a plane."

"Then he's never flown before?" Strange asked sharply.

"Never," replied Andre. "And I wager he insisted on Fonck, Henri Dornay, or another of the other great ones to pilot him—why, what is wrong?"

Strange had sprung to the door.

"Come on!" he clipped out, "I may be mistaken, but we'll take no chances."

Andre and the Jays dashed after him as he ran toward the conference room. Officers and orderlies stared as they raced by. Strange halted before a large door, seized the knob. The door was locked.

"Colonel Jordan!" he shouted.

There was no answer. He shouted again, then stepped back and lunged at the door. The Jays leaped to help him, and on the third attempt the door burst open. One window was open and the room was empty. Strange snatched up a card from the long conference table. It bore the red devil symbol and underneath was scrawled:

"Received: Two moth-eaten colonels —Monsieur Ie Diable."

STRANGE whirled to the officers who came running into the room. "Turn out the guard! Flash an alarm not to let anyone off the post!"

"But what's the matter?" gasped a bald-headed major.

"Matter?" howled Andre. "Monsieur Ie Diable has stolen the chiefs of French and American Intelligence!"

Pandemonium broke loose, and the officers scattered, yelling for orderlies. Strange ran to the window, shouted at an enlisted man crossing the three-sided court.

"Did you see anyone just leave the compound?"

The man hurried toward him.

"A car almost ran me down, sir—it came out of here a minute ago."

"What kind?" rapped Strange. "Which way did it go?"

"It was a big Staff car, sir—a closed Packard. I think it went toward Chaloncourt."

Strange spun around to Andre and the Jays.

"They've probably passed the sentries already. We'll have to spot it from the air. Tom, get out there and have a D.H. started—I want one with wireless equipment and interphones. Noisy, you run to the wireless room and be ready to relay Andre's directions by phone to Chaloncourt and all the road patrols."

The Jays sprinted down the hall. Strange wheeled to the bald-headed major who had remained in the room.

"Conroy, warn everyone in the search —the road patrols especially—to stop that car even if they see Pershing himself in there!"

"But I can't order that!" Conroy said, aghast.

"It won't be Pershing," snapped Strange. "Karl von Zenden, the notorious spy called the 'Man of a Thousand Faces,' is in that car. Don't let him trick you!"

Conroy gulped, hastily departed.

Strange made for the compound, with

Andre trotting breathlessly beside him.

"Do you think von Zenden is Monsieur Ie Diable?" the little major demanded.

"No," Strange tossed back, "but he's impersonating your M. Devil, that's certain. And he played the role of Lamotte, too."

"Mon Dieu!" groaned Andre. "If this gets any worse I shall go mad. And to think of it, stealing colonels like so many sacks of potatoes!"

A D.H. was being hastily warmed up, and several Spads had been started when they reached the hangars. Strange singled out Tom Jay as he buckled on a helmet with earphones.

"Tell the pilots to spread out in a ten mile circle and cover all roads."

He vaulted into the front pit of the D.H. as Tom yelled an answer. Andre tumbled in behind him, and mechanics pulled the chocks. The ship was already turned for taking off. He opened the throttle, and the bellowing Liberty hurled the heavy plane down the field. As the D.H. climbed, he banked over the highway to Chaloncourt. It was almost twilight, but there was still enough afterglow for him to see along the winding road. Motorcycles from the base were racing toward the town, and he could see two or three supply trucks but not the fleeing Staff car. He then banked toward a highway which skirted Chaloncourt.

Suddenly Andre thumped at his back, stabbed his finger toward a crossroads. A car had stopped at the intersection. As Strange nosed down, the Frenchman swerved the tourelle. A burst smoked down info the highway, kicked up dirt a hundred feet from the machine. The car lunged to one side, made a wild turn away from the town. Strange, peering down intently, saw that it was a khaki-colored Dodge touring-car. Before he could warn Andre, the Surete major pounded out another blast. The driver of the A.E. F. car skidded into a ditch and jumped out. As he ran for cover, a portly officer clambered from the rear and followed, shaking his fist at the D.H. Strange hurriedly curved away.

"Hold on, Andre!" he shouted into the interphone speaker-horn. "That's Colonel Beeding."

"But maybe it is von Zenden masquerading," yelled Andre.

"No, it's the wrong car—wait! that man in the compound might have been planted to put us on the wrong track! Call Noisy—tell him to have all cars stopped and searched—even the trucks!"

While Andre pounded the key, Strange dived over the Dodge again. He plunged so close that he could tell there was no one else in the machine. Beeding and the driver were huddled under a tree. Convinced of their identity, he zoomed, turned to follow the north road.

"Any report from Corps?" he said anxiously.

"Coming now," replied Andre. There was a click in Strange's phones, as the Frenchman cut him in on the receiving circuit. He mechanically translated the swift flood of dots and dashes, while he watched the road. The message ran:

Strange peered over the side of the cockpit. Lights were flashing on all the roads, and Corps motorcycles were speeding back and forth. He looked over the other side, toward the town. A train was just pulling in from the northwest, and for a second he thought it was the ace-train, then he recalled that Base Hospital Two was in the other direction. Evidently this one was a supply train returning empty from the area where the offensive. was to be launched.

SOMETHING tugged at the back of his memory, something connected with that railway. Abruptly he remembered. In that photographic glimpse of the Corps base, before he had zoomed away from the German Staffel, he had seen one of the new French Diesel-driven railway cars pulling onto a siding. The sidetrack had been one of several leading to the supply sheds and tents at the southern end of the base. He banked hastily and flew back over the tracks.

"What now?" demanded Andre.

Strange crisply explained. Andre gave an exclamation.

"That must have been de Soucy's private car! He was using it in this sector."

"Unless I'm way off, von Zenden's using it now," Strange answered. "Watch for it when I drop a flare."

He jerked the release, and bright light spread through the darkening sky. As he nosed down, he saw that the Diesel car was gone, and in the same moment Andre pointed excitedly along the tracks. Strange looked, saw the Staff automobile. It had been driven a hundred yards along one track, straddling the rails, and was obviously abandoned. Searchers crossing the tracks farther down would have failed to see it in the gloom, even if they had glanced up the tracks.

"You're right, mon ami!" Andre burst out. "But which way did they go?"

Strange rammed open the throttle, heading south.

"They had to go this way—they'd have run into that supply train if they'd gone north. Call Corps again, tell them about this and to rush a flight of Spads down this way."

Andre bent over the key. Strange kept the Liberty wide open, holding the two-seater at a hundred feet. Von Zenden would undoubtedly transfer his prisoners to an automobile at the first opportunity, but at this speed there was a good chance of overtaking the car first. The lights of a signal tower flashed toward them, disappeared behind the thundering ship. Strange spoke quickly into the interphone horn.

"Andre—ask Noisy the call and wavelength of the ace-train wireless. Call the train and warn them to be on the lookout!"

"Noisy has already thought of it,"

Andre exclaimed. "He is calling the train now. We can listen to what they answer."

Strange's phone clicked, and he caught part of the Corps message:

Almost at once the answer came from the ace-train wireless:

There was a break, then a crazy jumble of dot and dash signals from which Strange caught a few broken words:

One last signal buzzed into the phones, as though something had fallen on the key of the train wireless, then it ended.

"Sacre bleu!" cried Andre. "What can have happened?"

"Call them again!" Strange rapped out.

The little Frenchman pounded the key. Strange listened anxiously as

Andre switched to the receiving circuit, but an ominous silence was tha only answer.

"HOW far are we from Tower 97?"

Strange said into interphone.

"About twenty-four kilometers," came Andre's hasty reply. "The train is between there and Amoins, and so must be the Diesel car, for there is Amoins ahead, and no sign of the car."

The D.H. thundered over the tracks which pierced the French town. There were sidings on right and left, and freight cars being loaded from ware-houses, for this was one of the new supply bases for the A.E.F. It was dark, but men with lanterns waved excitedly along the south track, and Strange surmised that the stolen Diesel car had raced through the base before the theft had been reported.

Amoins fell away behind the roaring two-seater, and Strange climbed a trifle higher to be sure of not hitting telegraph poles. None of the Spads was visible, but he knew they might be nearby, unseen in the deepening gloom. The tracks curved, straightened to cross a long drawbridge across the Molaine River. There was a hill beyond, but Strange kept low, flying through a cut which had been made for the railway.

"Only eight kilometers more!" Andre said tensely. "We should see the train in a minute or so."

He had hardly finished when high over the hills ahead there was a brilliant flash. A streak of rainbow fire shot across the sky, like the tail of a comet. It came apparently from nowhere, but it struck squarely into the wings of a diving Spad. Like a moth flying into a candle, the Spad blazed and plunged to the ground, streams of colored fire pluming after it. So dazzling was the flame that Strange could see nothing beyond. He heard Andre cry out in horror, as a second streak of the mysterious fire flashed across the heavens. Two Spads, one a Yankee ship, the other painted a bright red, were whirling frenziedly away from the rainbow flame. The streak of fire curved toward the khaki-colored Spad, and the wings blazed. The pilot leaped up in his cock-pit, dived from the flaming ship.

Suddenly, the rainbow streak whipped toward the falling man. It missed him by at least twenty feet, but weird colored flames instantly enveloped his tumbling figure. Strange shuddered. The mysterious stream of fire swerved back toward the red Spad, but the pilot wildly renversed and escaped. As abruptly as it had appeared the rainbow streak vanished.

Strange had zoomed to three hundred feet, twisting away from the flaming Spad. The burning figure of the unfortunate pilot struck on the side of the hill and fire spread through the grass. As the D.H. banked around above the river, Andre gave a shout. Strange flung a glance upward. By the glare of the falling flamer he saw a trio of black Halberstadt two-seaters.

All three of them were plunging after the red Spad. Andre swore through the interphone as the beleaguered ship dived closer.

"Mon Dieu! It is Henri Dornay those butchers are after!"

Strange had already recognized the gaudily painted ship of the wealthy French ace, and as the Spad hurtled past he saw the haggard face of Dornay himself. The young Frenchman was working madly to clear a jammed gun. Strange kicked around and loosed a burst at the first Halberstadt. The black ship skidded, but the gunner whirled his Parabellums for a raking blast. Andre crashed out a barrage from his Lewises and the two-seater pitched down with half of its tai} shot off.

DORNAY'S Spad shot up into a furious Immelmann and lanced in at the second two-seater. The German gunner dropped under a hail of bullets, and the pilot threw the black ship into a vertical bank. Its Spandaus ripped through Dornay's wings, and the French ace was forced into a hasty chandelle. The third Halberstadt was thundering down at him when Strange caught it in his sights. Jets of fire, pale against the blaze of the wrecked ships below, leaped from the trembling Vickers. He saw the pilot's head slam back against the crash-pad. The Boche slid out of sight, and the Halberstadt screamed down in a headlong dive.

It struck almost on the tracks, just as four Yankee Spads from Chaloncourt came racing to join the fight. The remaining German two-seater whirled and fled, with the four Yankee Spads after it. Dornay tossed a hurried gesture of thanks toward the D.H., then his red wings flashed off into the shadows. Strange drew a long breath, stared around at Andre. The Surete major's face was pale.

"It was that same hellish fire!" he exclaimed hoarsely. "But where did it come from this time?"

"I don't know," said Strange, "but we mustn't forget about the ace train and von Zenden."

He turned back and flew above the tracks. The blaze from the plane on the hill lit up the right-of-way, but only barren rails shone in the light. The D.H. was still in the light when three Nieuports with French cocardes appeared from the opposite direction. The French ships pulled up and circled, and the pilots motioned excitedly toward the track. Andre signaled back, pointing southward, but the pilots vigorously shook their heads.

"Bon Dieu!" Andre gasped through the interphone. "The ace-train has disappeared!"

"It's impossible!" Strange said tensely.

"Then where is it?" demanded the little major.

"It must have gone by during that fight."

"Non, non, I would have seen it," retorted Andre.

"Trains can't vanish," snapped the G-2 ace. "If it didn't get by us, it must have backed up—these pilots obviously missed it in the dark. Call Corps and tell them to get us a report from Tower 97—we'll fly that way."

The three Nieuports swung in to follow the D. H. Strange looked at them sharply.

"Keep your guns ready, Andre. Those pilots might be Germans."

"No, mon ami, I recognized one of them. They are from the 119th Escadrille—they are no spies."

The Frenchman bent over the wireless key. In a few moments the reply rattled into Strange's phones:

Strange and Andre stared at each other, then the G-2 ace banked the two-seater and sent it back along the rail-road. One of the Nieuports followed, and the pilot climbed steeply to drop a flare. Only empty rails were revealed. The two planes raced on. Lanterns appeared ahead, and Strange saw dough-boys spreading out along the right-of-way. A searchlight truck rolled to a stop at the next crossing, and a tunnel of light pierced the darkness.

Spad pilots from the Corps field were dropping flares at intervals, and from the Molaine River to Chaloncourt there was not a stretch of track or a siding left in shadow. But there was still no sign of the ace-train when Strange circled over the Second Corps base. He landed, switched off the Liberty. Several planes were idling on the line, and as he jumped out he saw five or six pilots hurrying toward the ships. In the van were the Jay twins.

"Where are you going?" he asked them.

"To look for the ace-train," Tom said breathlessly. "It's disappeared. They can't locate it anywhere."

"Stay here," cut in Strange. "Noisy, tell those other pilots not to take off."

"But Colonel Beeding ordered us out," protested Noisy.

"I'll take the responsibility. Tell them to shut off their engines."

The Jays ran toward the ships, and Strange and Andre started in toward the Corps flight office. Suddenly the little major stopped.

"Henri!" he exclaimed, and Strange saw the handsome French ace pacing nervously beside his red ship. At Andre's exclamation, Dornay turned and hurried toward them.

"I thought I had missed you, Andre," he said in a strained voice. "I have been trying hard to find you."

"You succeeded when you brought those black Halberstadts down on our necks," Andre returned with a grimace.

Dornay stared at him.

"So it was you in that D.H." He looked in surprise at Strange, as the G-2 ace pushed up his goggles. "And you were the other, mon capitaine? I owe you and Andre a thousand thanks. Those Boche nearly had me cornered."

"Why were they after you, Henri?" demanded the Surete major.

"I do not know. I came on them suddenly and they attacked. But could I see you alone—if you do not mind, Capitaine Strange?"

"Not at all," said Strange. "I'd like to check up on this missing train, anyway."

Dornay started.

"A train—missing? But how could that be?"

Andre expressively moved his hands.

"Monsieur Ie Diable comes along, and —voila!—the American ace-train vanishes, along with Colonel de Soucy's new private Diesel car."

"But this is preposterous!" said Dornay.

"And so is a rainbow fire that comes from nowhere and sets planes ablaze without even touching them," Andre said grimly. "Could you see what was back of it, or where it came from?"

Dornay shook his head.

"My only thought was to escape with ' my life. It must have been some new type of rocket. I could understand that —but that an entire train could vanish, no—I do not believe it."

"Well, perhaps there is word of it by now," replied Andre. "Let us go inside."

He and Dornay followed Strange into the Corps flight building. Major Conroy, the bald-headed Staff officer, was just putting down the telephone as they entered the flight office.

"Neville!" he jerked out, as he saw Strange. "Did you find the train?"

"No," said Strange, pulling off his gloves. "It wasn't between Amoins and Tower 97."

"But it's got to be!" groaned the other man. "It didn't go back past 97, and it never reached Amoins."

BEFORE Strange could reply, the door was flung open and the portly figure of Lieutenant Colonel Beeding appeared. Beeding's plump face was as red as a rooster's wattles.

"What do you mean by grounding those pilots I ordered up?" he shouted at Strange.

"I stopped them because they'd be in grave danger," replied the G-2 ace. He explained about the mysterious rainbow fire. Beeding's mouth sagged open.

"I don't believe it!" he spluttered.

"It's true, colonel," Conroy said unhappily. "We heard, a report, but I thought the ships had been shot down in flames and somebody just imagined the rest."

"I'll do the thinking around here!" Beeding said in a nasty tone. He glowered across at Strange. "You told Conroy that von Zenden was mixed up in this. How do you know that?"

"No one but von Zenden could have impersonated Georges Lamotte so well," Strange answered. He told Beeding as quickly as possible about the events of the afternoon. "It's obvious that von Zenden went there to get rid of the black corpse, after he learned it had been found and reported. He probably had the Breguet spy pilots ordered there to delay Andre and me, and when we downed the ship he had to work fast to get rid of Schermann's body and then escape. He must have knocked out old Lamotte before the air fight—probably after the old man helped him take the corpse inside. When we came, he impersonated Lamotte long enough to be sure that the black material was about to ignite, then he ran out and put the old man's clothes back on him, left the body where we'd see it and escaped into the woods while Andre and I were inside. I guessed the truth when Lamotte's shoes fell off as I was carrying him, and I saw his clothes had been hastily fastened on him."

"So you guessed all this!" snapped Beeding. "Well, if that's all you've got to go on—"

"It's not," Strange said coldly. "There was another impersonation. Some one came here in a plane as Colonel de Soucy, and Andre says de Soucy never flew in his life. It's obvious that he was captured soon after the Diesel car was put on the siding, and that the imposter came up here to get Colonel Jordan alone so he could find out how much we'd learned. The colonel may have seen through the deception, but at any rate he was slugged and taken out at once through the window. Von Zenden evidently had spies waiting with the Staff machine, so they could rush Colonel Jordan to the Diesel car."

"Well, what happened to that car and the ace-train?" demanded Beeding.

"Maybe," Strange grinned, "Monsieur Ie Diable has made off with both of them."

Beeding purpled.

"Do you think I'm a fool? How could one man—even a thousand men—steal a train?"

"According to what I've heard," said Strange ironically, "he's stolen about everything else. Why not a train?"

Beeding swore. Henri Dornay had stood beside Andre, listening with a dazed expression.

"But all this idea of M. Diable does not make sense," he objected. "According to what Andre used to tell me, the man was only an eccentric—a Rames type of person who amused himself by baiting the police."

Strange looked at him, then nodded.

"You're undoubtedly right—but von Zenden for some reason has taken advantage of the reputation our unknown M. Devil built up."

"Why?" Beeding broke in harshly. "What possible reason could he have for all these crazy antics?"

Strange gave him a cool glance.

"I won't try any more guesswork, colonel. But if you'll let me see those lists which Colonel Jordan said you were bringing, showing Monsieur Ie Diable's accomplishments—"

The hasty entrance of Lieutenant Peck cut him short. There was a triumphant smirk on Peck's face as he saw Strange.

"I just found out who flew that D.H., Colonel Beeding. It was Captain Neville."

"What!" roared Beeding. He spun around furiously. "So that's the answer, is it? This whole thing is a trick to—"

"It was a mistake," Strange said curtly. "We were trying to spot the Packard, and in the dusk—"

"I ought to have you court-martialed for carelessness!" Beeding rasped. "If it weren't for this case—Conroy, answer that phone!"

The bald-headed major hurriedly obeyed. In a few seconds he dropped the instrument, gaped at the others.

"The bridge! Why didn't we think of that?"

"What is it?" snapped Beeding.

"The drawbridge over the Molaine River—they just found the bridge-tender murdered, with one of those red devil cards on his body. The bridge was not quite closed. Somebody must have opened it and let the ace-train plunge into the river!"

"Sacre Dieu,!" moaned Andre. "Then the Diesel car also went through the draw—and both our colonels have been drowned!"

A STUNNED feeling came over Strange. In his long association with Jordan he had come to know the courage and kindness back of the G-2 chief's brusque manner, and the thought of his loss numbed him. In a daze he heard Peck speaking again to Beeding.

"—something else, sir. My sergeant just found this in the conference room. It seems to be part of a confidential memorandum from Colonel de Soucy to Colonel Jordan."

Beeding took the sheet of paper, frowned, handed it to Andre.

"My French isn't very good; would you mind translating this?"

Andre ran his eyes over the first words.

"Oui, this is the colonel's writing. It is about M. Ie Diable, and it says:

Andre's voice trailed off, and Strange suddenly realized the hush in the room. He stared around. Beeding's lips were working convulsively.

"You damned traitor!" he burst out. "No wonder you were so anxious to blame all this on von Zenden."

Strange looked at him in genuine astonishment.

"Surely, Colonel Beeding, you don't think I'm Monsieur Ie Diable?"

"You can't bluff your way out of this!" stormed Beeding. He reached out and snatched at Strange's .45. Strange made no attempt to resist him, and Beeding backed away, the pistol gripped in a not too steady hand.

"Wait, mon colonel," Andre said in a distressed voice. "There is some mistake—he could not be a traitor, after all he has done against the Boche."

"How do we know what he's done?" fumed the Staff officer. "He goes on freelance missions and makes reports without any proof half the time. Jordan may have been fooled, but I've suspected him from the start."

"But the memorandum does not-mention his name," protested Andre. "It is ridiculous to suspect him."

"He's bamboozled you the way he has the rest," snapped Beeding. "I happen to know he was in France in 1914. He was working with make-up and disguise—I heard him admit it to Jordan one day—said it was for his own amusement. And he's been on leave for weeks—supposed to be down in Italy. It's plain as the nose on your face that de Soucy meant him and nobody else. He's back of the whole business and now he's killed Jordan and de Soucy and wiped out those aces."

"But he was with me when Colonel Jordan was abducted," insisted the Surete major. "And in the fight to save Dornay he shot down a German ship."

"He was covering up," said Beeding harshly. "Use your brains—he fooled you at Lamotte's house and he's been using you as a shield ever since. That Breguet was probably sent by Colonel de Soucy, and Strange knew he was caught unless he brought it down."

Peck had started at mention of Strange's right name. Beeding jerked his head imperiously.

"Call the guard, lieutenant, but not a word as to the prisoner's true name. I'm going to keep him incommunicado until he talks."

"And meantime you're letting von Zenden cover his trail," Strange said calmly. "Give me twenty-four hours and those lists from G.H.Q. and I think I can bring you the answer to all this business."

"You mean you'd be safe in Germany by then!" snarled Beeding. He wheeled as Peck returned with a guard sergeant and two men. "Lock up this prisoner, sergeant. He's charged with murder and treason!"

THE cell was dark, but on a small table in the corridor outside a lamp was burning. Behind the bars, Philip Strange watched the exasperated face of Lieutenant Colonel Beeding, who for upward of an hour had been alternately threatening and pleading.

"Now see here, Strange," Beeding rasped, "you're in a tight spot. If I press these charges you'll be court-martialed and shot."

The G-2 ace shook his head.

"With all the actors in the Allied Armies," there could be a hundred men to answer de Soucy's description. Your evidence is flimsy, colonel. If it weren't, you'd have pushed the case immediately."

Beeding turned red, but gulped down his wrath.

"I'll make a bargain with you," he mumbled. "I'll give you all the information you asked for, and you can direct the affair from here. Prove your innocence and you go free."

"What you really mean," said Strange, "is that you're in a jam with Chaumont; they've probably given you a deadline for finding out what's back of all this."

"There's nothing back of it," snapped Beeding, but Strange could see he had scored a hit. "Getting rid of Colonel Jordan and those aces was a big enough stroke in itself."

"Then something's happened since the offensive started?"

"No, but G.H.Q. is afraid—" Beeding stopped, glaring through the bars. "If you've figured out anything, I demand to know what it is."

"The answer is still the same— twenty-four hours and a free hand."

"No!" snarled the Staff officer. "It's my way or not at all."

Strange coolly returned to his iron bunk and lay down. Beeding fumed and swore for a minute, then stalked down the corridor. Strange heard him berate the guard for slowness in opening the door, then the door clanged.

Strange closed his eyes, but sleep was impossible. Wearily, he went over the events which had occurred since his departure from Italy. A full day had passed since his arrest, and he had considered the tangled situation a dozen times, but Jordan's death had left him with a sense of unreality and his brain was still dulled.

A minute or two had passed when he heard a stealthy sound. He opened his eyes, sat up quickly as a man in a flying-coat became visible outside the cell. To his astonishment, the man's face was completely covered by a black mask, the top of which was thrust under his leather helmet.

"Stand up," the intruder whispered, "and don't talk."

He shifted an automatic to his rubber-gloved left hand, produced a ring of keys and unlocked the cell door. Swinging the door open, he motioned Strange outside.

"Walk ahead," he ordered in a harsh whisper.

Strange looked intently at the eyes hack of the mask-.slits, then obeyed without a word. There was a smell of chloroform as he neared the corridor door, and he saw the guard stretched on the floor, unconscious. The masked man prodded him on through, and toward a hall on the right. It was unlighted, but a barred door was dimly visible at the end. The masked man unlocked it, and they went outside. A closed Renault stood in the darkness, a few yards away. Strange saw a metal pennant on the hood, and he thought it bore the tri-colors of France.

"Get in the rear and under that rug," his captor ordered in a low tone. "Stay there and keep still."

Strange lay down and pulled the rug over him. He felt the car start, go a short distance and stop. He could hear indistinct words between the driver and a sentry, then the machine rolled on. As it gathered speed he sat up cautiously. The car's headlights were turned off, but the dashlight was on and he could see the other man readjusting the mask he had evidently taken off before reaching the sentry-post.

"You needn't bother with that, Henri," he said.

The driver started, dropping the mask, and Strange had a glimpse of Dornay's clear-cut profile against the dashlight.

"Then you knew all the time?" the French ace exclaimed.

STRANGE climbed over beside him. "I had a strong suspicion last night, when Andre read de Soucy's memorandum. And you were a trifle too quick to defend M. Ie Diable as a mere eccentric playing tricks on the police."

Dornay groaned.

"I may as well admit it, I was the original Monsieur Ie Diable. But if you suspected me, why didn't you say so then?"

"No proof," said Strange, "and it was evident you had nothing to do with the present mixup."

"I swear I know nothing of it," Dornay declared fiercely. "I played the part before, oui—I was young, reckless, bored with Paris and with too much money. It was a lark for a while—I did it mainly to see how long I could fool Andre. We were friends before that, and I used to come in and listen to him rave about what he would do when he caught M. Diable. I used some crude disguises—nothing that would have deceived an expert—and when I needed help I hired some Apaches from whom I thought I had concealed my identity. Then the war came and I became a pilot. I thought Monsieur Ie Diable was forgotten, and I was on furlough at Nice when I first heard he had come back.

"I returned secretly to Paris and tried to find some of the Apaches I had used. Then I learned that Colonel de Soucy was also investigating, and I feared he would trace the earlier things to me and blame me with all the rest. I determined to find Andre and make a clean breast of everything, but I lost my courage when I heard de Soucy's memorandum. I was afraid no one would believe me. Later, I recalled your request for twenty-four hours' freedom to clear up the puzzle, so I decided to release you, hoping you could prove me innocent of any treason."

"Very kind of you," Strange said drily, "and of course it never occurred to you that my escape will be taken as sure proof of my guilt."

"I have already cleared you," Dornay answered. "I sent a complete confession to the caretaker at our old estate, and Andre will have it by now. At my request he agreed to go there tonight with those mad twin aides of yours, though I did not say why. I was afraid they might be accused of helping you escape, if they were at Chaloncourt."

Strange looked at him a moment, then held out his hand. Dornay grasped it quickly.

"Then you forgive me, mon capitaine, for forcing you out of the guardhouse?"

Strange grinned. "To tell the truth, I was getting a little tired of the place. By the way, where are we going?"

Dornay had turned southward on a road which skirted Chaloncourt.

"To the estate I mentioned. You may have heard of it. It is about forty kilometers southwest of Amoins, at the edge of the Foret des Charnes. We can have privacy there."

"I thought you had turned that chateau into a hospital," said Strange.

"No, it is a home for blinded poilus," replied the Frenchman. "But the attendants are my old servants, and they will not talk. There is only one thing— the 144th Spad Escadrille is temporarily stationed on the estate, and we shall have to avoid the pilots who might have met you. However, the escadrille is almost a kilometer away from the chateau, so there is no real danger from that source."

They were approaching another sentry-post. Strange hid in the rear until Dornay had displayed his pass and driven on.

"Has Andre the lists I wanted?" he asked as he climbed into the front again.

"No, I have them here," said Dornay. "I made away with them while your fat lieutenant colonel was trying to browbeat you tonight."

Strange laughed.

"A man of your talents should be in Intelligence, Henri. Before I look over these, tell me if anything unusual has happened since last night."

"Only that the offensive has begun, and is meeting with great resistance. Andre tried to discover the source of that rainbow fire, but did not succeed. I think it must have come from a plane."

Strange was silent a moment.

"Have they recovered any of the bodies from the train, or thg Diesel car?" he asked soberly.

"No, and I am afraid they will never be found. There was no time to grapple from the bridge—troops and supply trains were being rushed through after midnight, and it will be three days before heavy barges can be towed into position. By then the quicksand may have swallowed everything. A diver was lowered this morning, and he failed to locate the car or the train, but his search was cut short by defective apparatus."

THE G-2 ace stared at him, then hurriedly bent over and began to read the first typewritten sheet by aid of the dashlight. Dornay drove as fast as he could, avoiding the main roads on which troops and supply trucks were being moved. Twice, Strange had to crawl into the rear at sentry-posts, and each time he waited tensely for fear his escape had been discovered and road patrols warned. But they passed safely, and at last turned into a side road which led to Dornay's estate.

He had almost finished the detailed reports Dornay had purloined. Thumbing back over the pages, he hastily checked off certain paragraphs.

"What have you found?" the Frenchman said anxiously.

"Listen to these items," Strange replied, "A railway official 'stolen' at Barle-duc—the one who had charge of personnel appointments from Nancy to Chaloncourt; a ration car loaded with food missing on the same line—supposed to have been missent to another division, but not found; a supply truck stolen at Amoins, contents three hundred French uniforms; an American truck near Amoins with a load of machine-guns and ammunition; a track walker on the Amoins-Chaloncourt section, disappeared. What do you make of all this?"

"Something is very wrong along that section of railway!" exclaimed Dornay. "It looks—Mon Dieu, you think the Boche has established a base inside our lines?"

"Exactly," said Strange. "This Monsieur Ie Diable business has been a blind. All those other thefts were intended to distract attention from the railway angle. That's why they made them as varied as possible and as widespread. Among all the others, these few things are almost lost. Except for last night's trouble I wouldn't have noticed them."

"But what shall we do?" Dornay said excitedly.

"Tell Andre as soon as possible, and get planes to searching this sector. We can use the Spads of the 144th."

Dornay recklessly switched on his lights and sent the Renault roaring along the road. They passed through a gateway, sped up a long, winding drive through a woods. The chateau came into view, a shadowy bulk beside a small lagoon. A crippled, white-haired man-servant answered Dornay's hasty pull at the bell and bowed effusively as they entered.

"Bon soir, Master Henri. Bon soir, monsieur."

"Hello, Jacob," Dornay answered. "You received my message?"

"Oui, but the three officers have not come," Jacob replied as he turned to secure the door.

Dornay looked at Strange.

"I hope nothing's gone wrong,"he said in an undertone. Then in a louder voice,

"We'll wait in the library, Jacob. Bring some brandy."

Jacob limped away. Dornay led Strange toward the library. They passed the drawing-room, and Strange glimpsed a number of poilus, some in wheel-chairs, a few talking together, some listlessly silent, staring before them with the empty expression peculiar to the blind.

"Poor wretches," Dornay said in a lowered voice. "I think I would prefer death."

Strange looked around as they entered the library.

"Have you a railroad atlas?"

"I think not," said Dornay. "I am here so seldom I forget what is here— but if you are looking for a railway map of this province I have an old one. I remember it because my father used to keep it up on the wall when we operated the mines."

"What mines?" Strange asked sharply.

"Why, the old Latierre coal mines," said Dornay in surprise. "I supposed you knew of them—they were the main source of the family fortune, before they filled up with water."

"Are they near here?" Strange said quickly.

"About three kilometers, at the southern edge of the estate. Here, the map shows them."

Strange took one swift look at the map Dornay brought out.

"These sheds, and the spur tracks— are they still there?"

"Yes, I suppose so, but they haven't been used for—" Dornay broke off, paling. "Sacre nom! You mean the Boche may be hiding there?"

"It's the most likely place, with that railroad hookup. It would explain a lot of things."

Dornay groaned.

"If this becomes known, all France will think me a traitor."

"Not if we move quickly. You can persuade the escadrille pilots to help us; we'll cover the place from the air while the ground men cut off their escape."

DORNAY sprang to the door, almost knocking over Jacob, who had arrived with the cognac and glasses. A poilu, feeling his way along the hall with his cane, paused uncertainly as the door thudded against the wall. Dornay stepped out of his path, turned hastily to the white-haired servant.

"Jacob, have you seen or heard anything going on at the old mine?"

Jacob looked surprised.

"No, Master, Henri. What could anyone want there? They have been deserted for years."

"You're sure the place is deserted now?" Strange interrupted.

"I could not be certain, monsieur, not having been near it, but—"

"If you haven't been near it,"

Strange said softly, "where did you get the coal-dust on your shoes?"

The tray dropped to the floor with a crash, and Jacob leaped back. He plunged one hand under his coat, and a pistol came into sight. Strange's iron fingers closed on his wrist, and a sudden jerk sent the gun to the floor. Before the man could twist free, Strange reached up and snatched at his snow-white hair. It came away, revealing a close-cropped head and a smooth forehead where makeup wrinkles ended.

PHILIP STRANGE smiled grimly at his captive.

"A very good act, von Zenden—almost as good as your role of Lamotte."

For an instant, pure hate showed in the Prussian's eyes, then a veil of mockery hid it. He inclined his head ironically.

"Thank you, my dear captain. It is a pleasure to play before such an appreciative audience."

Dornay was staring open-mouthed at the notorious impersonator.

"But—name of a name!—what has happened to Jacob?" he said to Strange.

"He's probably locked up somewhere in the house," replied the G-2 ace. "With all these blind men, it would be easy to maneuver—"

He broke off with a sharp exclamation.

"Look out, Henri! Back of you!"

The supposed blind poilu had lunged forward, his cane uplifted. Dornay jumped aside and caught the blow on his shoulder. In the same moment, von Zenden dived for the gun he had dropped. Strange hurled him over back-ward, scooping up the pistol before von Zenden could recover his balance.

The man in poilu uniform was trying to draw a gun. Dornay's fist caught him a glancing blow on the jaw. He stepped back and tripped over a fold in the rug, but even as he fell he jerked out the weapon. Strange fired, and the spy's gun slipped from his shattered hand. Above the wounded man's howl sounded a rush of feet, and into the hall dashed a dozen men in the garb of poilus and attendants. Eyes no longer vacant glared over Luger pistols.

Dornay had retrieved the first spy's gun. He 'blasted a shot at the first charging German, aad the man went down with a blood-curdling yell. Another spy, with a bandage pushed up from his eyes, leaped over the fallen man. Strange shot him down, whirled to aim at two more plunging at Dornay. Von Zenden had regained his feet, was shouting for his agents to take the two men alive.

A huge figure in the white coat of an attendant hurtled against Strange from the side. He went down with a thud, but held onto his gun. The spy's distorted face was within an inch of his as he pulled the trigger. The man stiffened as though an electric current ' had passed through his body. A horrified look came into his eyes, then he slumped down and Strange felt warm blood on his hand. He fried to squirm from under the dying Boche, but a furious kick took the breath from his lungs. He saw a booted foot flash out toward his head. A sharp pain shot through his brain, and the snarling voices faded into a sudden blackness.

It seemed only a moment until his senses returned, but when he opened his eyes he was lying doubled up on the floor in the rear of the Renault, his hands tied behind his back. He could dimly see Dornay, also bound, and von Zenden on the seat beside him with a Luger in his hand. The Prussian was still made up as Jacob, and he had replaced the white wig.

"Faster!" Strange heard him snap at the driver. "Turn on your lights—there is no danger, now that the escadrille has been captured."

The lights went on, and the Renault's speed increased. Strange narrowed his eyes, and forced his aching brain to concentrate on von Zenden's words.

"You may as well answer my questions," the Prussian was saying to Dornay. "I shall learn the information, anyway."

The French ace maintained a stubborn silence. Von Zenden shrugged.

"Very well, if you choose to be pig-headed. But at least, permit me to thank you for creating the role of Monsieur Ie Diable. I could not have asked for anything more perfectly suited to my plans."

In the reflected glow from the head-lights, Strange saw Dornay's lips tighten. Von Zenden laughed.

"Where is your sense of humor, M. Devil? You must have had one in those earlier days. It was quite a touch, stealing the guillotine. I remember being amused by it even then, and thinking it would be pleasant to meet this gay desperado."

"Too bad I did not save that guillotine for your neck!" Dornay exploded.

"You should have covered your tracks more thoroughly," mocked von Zenden. "But at that, the truth might not have come to light it I had not put my wits to work. You see, it was necessary to know everything concerning you, after our discovery about your mine."

Dornay looked at him blankly. Strange caught the quick relief on von Zenden's made-up face.

"We are safe, Franz," the Prussian called to the driver. "I can see he knows nothing of the secret, and Captain Strange would have told him if he had suspected."

"But what if they learn that Dornay was the one who released the verdammt American?" growled the driver. "They will think of this place and send men here to search."

"That stupid Deeding could not add two and two," von Zenden replied contemptuously. "I wager we shall be in operation before they even discover their prisoner is missing."

"Ja, but what of the last message from Chaloncourt? If the Yankee chemist should analyze the smudge on that handkerchief accurately—"

"Stop worrying," snapped the Prussian. "The offensive is keeping them busy, and there is less than two hours before we strike."

THE other man grumbled something, and the car raced on. In a minute it slowed, began to bump over rougher ground. A violent jerk banged Strange's head against the floor and he groaned in spite of himself. Von Zenden bent over quickly.

"Ah, our sleeping beauty awakens. You have a hard skull, mein Freund."

Strange did not answer. The driver spoke nervously.

"We are coming out of the woods, Excellenz. I had better turn off the lights, unless you think the prisoners—"

"I can handle them if they try to get loose," cut in von Zenden. "But drive as fast as you can."

The car bounced and jolted along in the dark.

"I hope, my dear Strange, you are not too uncomfortable," the Prussian said suavely. "It may bolster you up to know that a surprise awaits you."

"I have an idea what it is," Strange retorted curtly, to cover his desperate attempt to free his hands. "That was a clever device, having the bridge-tender murdered and leaving the bridge partly open."

"Thank you," von Zenden said mockingly. "I was afraid, last night, that you might see through it—that is why I left part of de Soucy's memorandum, after I noticed how aptly it fitted you. Colonel Jordan, of course, would never have been fooled, but I knew I could rely on Beeding."

Strange tugged fiercely at the rope which bound his wrists. He could feel the knot loosen, and one hand was partly through the loop when the car stopped and several men surrounded the car.

"Is everything all right, Excellenz?" a guttural voice queried.

"Perfect," said von Zenden. "Have these two put with the other prisoners."

"The ones down in the mine, or in the coach?" asked the other man.

"In the coach," directed the Prussian as he climbed out of the car.

Strange and Dornay were dragged out and placed on their feet. They were marched around a huge slag heap and between two railway tracks, on one of which a locomotive bulked in the darkness. It had been moved part way from under a long, gloomy shed, so that the smoke from the st.ack could escape into the air, but the cab was inside and its. windows covered with canvas to hide the light from the firebox.

A faint glow shone back over the tender, revealing a freight car from each side of which projected the short, thick nozzle of a flame-thrower. Both the sides and roof had been armored with iron plates, through which ports for machine-guns had been cut. Through an open door, also armored, Strange saw enormous tanks connected by flexible tubes with the flame-throwers. Men in dungarees were inspecting the control apparatus, under the guidance of a grim-faced German officer.

Standing on the other track, and just inside the shed, was a combination engine and coach, hooked up with three or four passenger cars. In spite of his predicament, Strange felt a surge of relief as he recognized the missing Diesel car. The passenger cars were clearly those of the lost ace-train, the engine of which had been hooked to the armored freight-car.

Men in French uniform were busily loading machine-guns, ammunition, and grenades into the coaches, carrying them from trucks which had been driven under the sheds. By the faint light of their working-lanterns, a solitary car was visible at the far end of the second track. Boards had been spiked over the compartment doors and windows, and two sentries stood guard.

At von Zenden's command, one sentry unlocked a heavy padlock and opened the door at the nearest end.

"I trust you will have a pleasant reunion," said the Prussian.

Strange and Dornay were shoved into the poorly lighted passage, and their bonds cut. As the guards shut and slammed the door, a head was poked cautiously from. the nearest compartment.

"Phil!" Noisy Jay said in astonishment.

TOM JAY and Andre popped into sight, followed by Jordan and the long-faced French colonel, de Soucy. Strange shook his head at their hopeful expressions.

"Sorry, we're prisoners, too." He smiled crookedly at the G-2 chief. "But it's good to find you alive, colonel—even if you are in von Zenden's hands."

"That damned Hun!" Jordan grated. "Took me in completely with his impersonation of Colonel de Soucy. Black-jacked me the second my back was turned. Thought the colonel was a traitor when I came to in that Diesel coach—until I saw; two of him and knew what had happened."

De Soucy gave Andre an acid glance.

"How you failed to guess the truth I still can't understand. Everything hinged on the statement of one man— the signalman at Tower 97."

"But I tell you the three French pilots misled us," protested the little major. "I know now that the one I recognized must have been in von Zenden's pay and the others were spies— but when we learned about the open bridge—"

"There's no use going over all that," snapped Jordan. "We're here, and if we don't make a break pretty soon it'll be too late. Strange, is there any chance that our men will follow you here?"

"No," Strange answered. He hesitated, went on carelessly. "Colonel Beeding released me, and I got in touch with Henri. I asked him to get Andre, and the Jays here." He added a brief explanation of their capture, then looked at Andre. "Did anyone know you were coming to Dornay's place?"

"Not a soul," Andre said disconsolately. "We came like lambs to the slaughter. Von Zenden and those 'blind men' of his seized us the moment we entered."

"I can't understand it," Dornay muttered. "I was there two days ago, and nothing seemed wrong."

"They sneaked in last night," Jordan growled. "I heard von Zenden give the orders. Your servants and the real poilus were to be penned up in the basement, so there'd be no chance of their hearing any scrap if they had trouble taking over the escadrille."

He looked toward the padlocked door, then lowered his voice, "De Soucy and I have been working on a way to get out of here. Tom, keep a watch and warn us if they unlock the door."

Tom Jay nodded, and Jordan led the others back to a compartment midway of the coach. He rolled back the strip of carpet and pointed at a small section of the floor, from which several screws had been removed.

"It's a trap for oiling and inspecting the lighting dynamo. There's a metal casing around the dynamo, but it's fastened with screws, too. If we can get it off without their hearing us, we can squeeze past and under the car."

"What good will that do?" said Dornay. "The place is swarming with men and we have no guns."

Jordan and de Soucy looked at each other in dismay.

"Then they must have come up from the mine!" exclaimed the French colonel. "That means they are ready to strike."

"We'll have to get a move on us," snapped Jordan. He warily lifted the edge of the trap, and Noisy Jay hastily set to work on the screws which held the dynamo casing.

"How much do you know of their plans?" Strange asked Jordan in a low voice.

"Just about everything," grunted the G-2 chief. "What we didn't guess, after seeing this layout, Meade told us before he died. They had him in here—he'd been shot trying to escape. The whole scheme is based on some peculiar kind of coal dust in the mine. Dornay, you must know something about that."

THE French ace started. "The explosive dust! Oui, but how could they get at it when the mine is filled with water?"

"What about this dust?" interposed Strange.

"It was discovered when the miners opened a new seam, years ago," Dornay explained hurriedly. "It was composed of highly volatile hydrocarbons, and when it crusted on the walls there was spontaneous combustion. Experts said it was from too rapid oxidization when the particles were brought into contact with the air. There were several small fires, but they were brought under control—"

"Were the flames rainbow colored?" Strange asked swiftly.

"They may have been; some coal tars burn with bright colors. I remember only that the miners were afraid of the coal dust and the gas which accompanied it. Then one day there was a terrific explosion, almost as bad as the Oaks colliery blast disaster in 1866, and more than three hundred men were killed. The whole mine had to be flooded —they later blasted connections with the Molaine River at three places, trying to drain the shafts, but there was a leak well underground too, and they never could get the mine empty."

"And it's not empty now," muttered Jordan. "But a lot of that explosive dust, or some derivative of it, has floated to the top of the water, about three hundred feet down that nearest slant chute. From what Meade told us, German spies had been using the mine for a meeting-place—they were landed and picked up by planes at the place where the escadrille recently moved in. One of the spies got some of the stuff on him by accident, and when it dried out it ignited and burned him to death. A Boche chemist came over and saw possibilities if they could use it in flame-throwers, but they couldn't dope out any way to get large amounts of it into Germany. It's evidently dangerous to transport except in closed tanks. They figured a scheme to use it from a train, running along a main line between Allied supply dumps and important headquarters."

"So that is the answer!" Dornay said. "That is why they put the flame-throwers on that car!"

"It's a lot worse than it sounds," Jordan said grimly. "Meade said they tested a little of it over in Germany, and with special blowers they can throw a stream of it more than a hundred yards. The devils will be able to wipe out nine-tenths of the supplies we've brought in for this offensive. They can set fire to Amoins and Chaloncourt and burn to death any troops that try to get near them. And that Diesel car is to be hooked up to the cars from the ace-train—this one's got a defective air-brake or they'd use it, too. They're going to be crammed with Boche machine-gunners, enough to cut a hole through our lines from the rear. Nobody will suspect a thing until those two train-loads of hell drop into the middle of everything. Their spy in Tower 97—he was appointed by another spy after von Zenden got rid of the division appointment official—is going to send them word when they'll have a clear track."

"You're sure they're not planning to project the stuff from planes?" Strange said anxiously.

"Not tonight, but as soon as they can take over this sector," answered Jordan. "A captured Handley Page took on a small supply last night for a test, after landing more gunners here for their drive. From what Andre said just before you came they must have seen Dornay's ship and thought he suspected. The Handley Page probably escaped to Germany during the fight you had with the Halberstadts."

"I should have seen through the trick last night," Strange muttered. "But the shock of hearing about that open bridge—"

"It was too cleverly planned," Jordan said glumly. "Von Zenden didn't miss a bet. He had to get hold of a train secretly, and by picking on the ace-train he made it a double blow and also made that seem the motive. He was smart not to steal it outright, until he'd got everybody to believing in this blasted Monsieur Ie Diable business with all those confounded stunts."

Dornay winced, and Strange saw him look sidewise at de Soucy, but the French colonel's face was expressionless. In the brief silence, while Noisy Jay removed the last screw from the dynamo casing, Andre shook his head.

"Against that Prussian devil, I am like a child. But I still do not see why Franz Schermann's body was floating in the Molaine and coated like that."

"Meade told us," said Jordan "that a German pilot went down the slant chute one night to see von Zenden, and fell into the stuff and was drowned. His body must have been carried through one of those connections with the river. That was at least ten days ago, so it was probably drifting all that time."

NOISY JAY looked up suddenly. "The casing's loose. Are you all ready?"

"Wait," whispered Strange. "There's no sense dashing out there without a plan of action. How many prisoners are down in the mine?"

"Must be close to three hundred," said Jordan. "They got all the pilots and special mechanics from the ace-train, after the spy at Tower 97 stopped it and a dozen Boche with tear-gas grenades and gas masks jumped on board. And tonight they got most of the French squadron the same way."

"If we could turn those prisoners loose," Strange began, but Andre shook his head gloomily.

"There is a machine-gun crew at the mouth of the inclined shaft, mon ami. I saw them as we were brought here."

From outside came the unmistakable sound of a locomotive starting to move. It was followed by the sudden rumble of the Diesel-car engine. Strange whirled to Andre.

"Tell Tom Jay to come with us. This is our chance for a break!"

As Andre ran forward, Noisy pushed the dynamo casing down. It slipped from his fingers, but the rumble of the two engines muffled its thud upon the ties. Noisy climbed headfirst through the opening, and Strange quickly followed. His belt caught, but he tore it free and crawled on hands and knees along under the car. As Jordan squeezed his stocky figure down past the dynamo, Strange made a hasty survey of the scene ahead.

Two guards with rifles were silhouetted against the faint light of a lantern at the right of the car. They had their backs turned and were watching the last few gunners board the Diesel-car train. Farther on, just discernible in the shadows, von Zenden and a small group of men stood by the Renault. Between this group and the two men guarding the prison coach were three Germans standing close to a Maxim machine-gun which was pointed down the mouth of the slanting shaft. A spotlight connected with the circuit of the prison coach shone down the incline, and Strange thought he heard the sound of angry voices farther down in the mine. An abrupt increase in the Diesel's rumble drowned everything, and he saw the spy-train slowly move from out of the shed.

He looked quickly over his shoulder. Jordan had succeeded in getting through the trap, and Andre and de Soucy were crawling along the track behind him. Dornay and Tom Jay had just climbed down. Strange spoke into Noisy's ear.

"I'm going to make a dash for that Maxim. Tell the others to split forces and grab the two sentries' rifles."

He did not wait for Noisy to answer. The locomotive and the armored car had been swallowed up in darkness beyond the sheds, and the Diesel-car train was picking up speed. With a prayer that the two riflemen would not look around, he got to his feet and ran toward the Maxim. He was within twenty feet of it when von Zenden's voice rang out furiously.

"Lieber Gott! Stop him, you fools— kill him!"

A RIFLE cracked, and a bullet snarled past Strange's head. The gun crew jerked around, and one of the trio leaped to the swiveled Maxim. Strange dived head first as the machine gun tilted down at him. The German's finger was on the trigger when a rifle cracked again. Noisy Jay gave a shout of triumph, and the Boche, shot through the head, slid to the ground and tumbled down the incline.

Pistols and rifles were crackling fiercely behind Strange as he lunged to his feet. The two remaining gunners were almost on him. The first man aimed a vicious blow at his jaw. He rolled his head, and the German's fist struck only a glancing blow. Before the man could recover his balance, Strange landed a furious uppercut, then dropped the gunner with a jolting right hook. Andre was dashing toward the other Boche. As the German wheeled, the little major let fly with a hunk of coal. It hit the gunner squarely in the teeth, and he tottered back with a howl.

Strange threw himself down behind the Maxim. Von Zenden and his group had stopped firing, but the Prussian's voice was audible from back in the darkness.

"Rush them from the other side! They're back of the first car-wheels!"

A dozen figures charged from the shadows. Strange squeezed the Maxim's trigger, and four of the Germans sprawled to the ground. Two more fell as the others fled madly for shelter.

As the Maxim went silent, a chorus of yells sounded from down the shaft. Strange cast a tense glance over his shoulder. The prisoners were scrambling up the incline.

"Excellenz!" screamed the man Andre had knocked down. "The prisoners are escaping!"

The engine of the Renault suddenly roared, and then von Zenden's frantic voice cut through the hubbub.

"The other way, Dumkopf! Make for the planes!"

Strange loosed a volley in the direction of the sound, though the Renault was hidden in the gloom. Some one gave a cry of agony, but the car raced away, apparently untouched. Colonel Jordan plunged out from under the prison coach, followed by de Soucy and the others. Strange jumped up and ran to Dornay.

"Where is the escadrille based?" he demanded.

"Back along the road to the chateau," exclaimed Dornay. "But we'll never get there in time."

"Yes, you can!" snapped Jordan. "There are two stolen trucks back in that next shed."

Tom Jay and the French ace dashed toward the shed. Strange caught hold of Jordan's arm as the first group of prisoners neared the top of the inclined shaft.

"That mob may think we're Germans! They'll know you and Colonel de Soucy!"

Jordan and the French colonel ran to intercept the infuriated men. Strange and Andre picked up the Maxim and put it aboard the first truck, as Tom Jay brought it lurching across the tracks. In another minute, with ten or twelve Yankee and French pilots crammed into the machine, they went thundering after the Renault. Tom drove recklessly, throttle to the floor, and it was less than two minutes when the canvas Bessoneau hangars of the French squadron loomed into sight.

There were flares along the line, and a score of Boche mechanics working frenziedly to get Spads started for von Zenden and his men. As the headlights of the truck swerved toward the row of planes, two of the pilots ran toward a gun emplacement. Andre and another Frenchman leaped from the truck with the Maxim, and a burst dropped the two Germans in their tracks.

STRANGE jumped to the ground, raced to the nearest man and snatched his Luger. Von Zenden had reached an idling Spad and was vaulting into the cockpit. He pumped two wild shots at Strange, flung himself down at the controls. The Spad hurtled past the flares and took the air in a dizzy climb. Strange ran to the nearest plane. A Boche pilot was half-way into the ship, and a spy-mechanic gave a yell of warning. The pilot clawed his pistol into shaking fingers, but his shot came a split-second after that of the G-2 ace.

Without a sound, the pilot collapsed beside the plane. The mechanic fled and Strange hastily climbed into the ship. A battle was raging behind him as he opened the throttle, but as the second truckload of pilots rolled to a stop, the few remaining Germans abandoned everything in a mad attempt at escape. Two had managed to follow von Zenden, and a fourth took off with bullets tearing through his wings.

Von Zenden reappeared, dived with guns blazing. Strange hauled back the charging-handles of his two Vickers, whipped into a turn with wingtips grazing the ground. The diving Spad came into his sights as he tripped the guns, and the Prussian pulled up swiftly. But as he did, four small bombs dropped from his racks, and four spurts of flame marked their contact with the earth. An idling plane went onto its nose, its tail blown off, and a second one suddenly blazed.

The other Germans had pitched down after von Zenden. Strange zoomed as his ship gained speed, and then with a violent renversement he streaked toward the railway tracks. As he had expected, von Zenden and the three Boche pilots tore after him. He zig-zagged hurriedly as a storm of tracers burst about him. Two of the Germans abruptly turned back toward the field, but Strange saw that his ruse had worked. Three Allied pilots were already in the air, and two more ships were taking off.

A moment longer two pairs of guns hammered behind him. The Spad shook under a terrific pounding, and for a second he thought he was finished. A flying-wire parted, whipped back across the pit. His goggles cracked but miraculously did not break. He thrust the wire aside, bent low and plunged toward the dimly seen tracks.

Darkness closed about him, and the murderous fire ceased. He stared back quickly, but not even a flitting shape was visible against the lights at the escadrille. He turned to the controls, sent the Spad thundering along a hundred feet above the tracks.

As the Spad roared on through the night, he felt for the bomb release toggles. They were set, and he knew the racks were full. His jaw tightened grimly. If only he could catch up in time ....

Tower 97 leaped out of the gloom ahead. The Spad was four hundred feet from it when a machine-gun flickered at the tower window. Strange clamped the trips and ruddered at the same instant. Stuffing flew from the crash-pad at his shoulder, then two torrents of Vickers lead plunged into the man in the tower, and the Spad zoomed clear.

Half a mile beyond, a searchlight probed up from a village near the railway. It poked skyward, but by its shifting glow Strange saw a fast-moving blur on the tracks. His pulses jumped. It was the Diesel-car train, and directly ahead of it was the flame-thrower train!

The searchlight dipped, and came near the train. Strange groaned. Two streams of flame leaped out to right and left of the deadly armored car. Like fiery rainbows, they struck into the village. On both sides of the tracks, houses instantly blazed. Strange saw the searchlight crew wither to the ground, vanish in the holocaust. The two trains raced on, leaving an inferno behind them.

Strange sheered away from the frightful heat, climbing steeply. As he nosed down again, two ships came plummeting out of the night. Guns winked murderously from the cowl of the first plane, but he held to his screeching dive. Those trainloads of hell were almost to the Mol'aine. Amoins was next, then Chaloncourt. If those devils were not stopped, twenty thousand soldiers and every man, woman and child in the towns along those tracks would meet a flaming death!

MACHINE-GUNS were spitting from the rear of the Diesel-train and the top of the flame-thrower car as he plunged closer. One of the Spads behind him suddenly fell off and spun. He kicked aside as a burst of lead from the flame-thrower car gouged his right wing. His remaining pursuer twisted in, guns spouting. Slugs ripped through the cowl, tore open the side of his pit. He whipped around with a swift fury. The made-up face of von Zenden glared at him over the other Spad's guns. Strange hurled a burst straight at the crouching Prussian. Von Zenden wildly zoomed, but with a crash his prop went to pieces under a flood of lead.

Strange whirled his tattered ship back to its course. Von Zenden was going down, but that meant nothing now. The leading train was in the narrow cut which led to the Molaine bridge. With stick jammed to the firewall, he pitched down at it. Abruptly, one of the flame-thrower nozzles twitched up toward his ship. With one hand on the toggles, he pulled the stick hard back.

Rainbow flame gushed skyward as the Spad screamed up from the train. Five hundred feet above the train, Strange yanked the toggles. He felt the plane jerk as the bombs fell from their racks. A scorching heat enveloped the zooming ship, and for an instant he thought the Spad would catch fire.

Then a muffled crash broke through the roar of the Hisso, and the geyser of rainbow flame swept down in a crooked arc. A louder crash rose above the furious hiss of the fire, and Strange looked down on a scene like some painting of Hades.

The flame-thrower train had jumped the track just as it reached the bridge. As he stared down, he saw the Diesel train smash into the blazing wreckage. The first car telescoped, throwing its occupants into the holocaust. The cars behind turned over and rolled down the bank into the river. The last one had barely disappeared when the first pier of the bridge collapsed, burned clear through. The flame-thrower car dropped into the water, dragging its engine with it, and was instantly lost from sight.

Like bright colored gasoline, the rainbow fire spread across the water. Here and there, men had come to the surface —only a few of the scores who had been in the coaches. The weird flames spread out over them, and they vanished.

A flight of hard-flying Spads came down over the spot, and he saw the awed faces of the Jay twins and Dornay and Andre, and others he did not know. Slowly, the rainbow flames on the water began to lose their brilliance. With a signal to the others, he turned and flew back toward the place where von Zenden had been forced down ....

IT was nearly dawn, but no one in the Second Corps conference room showed any sign of sleepiness. Strange glanced slowly about the room. The Jays were there, and Dornay, Andre, and Colonel de Soucy. Their eyes, like Jordan's were fixed on the captured Prussian spy. Von Zenden's make-up had been removed. Adhesive tape and bandages partly covered his features, but even his crash and resulting capture had failed to eliminate his mocking manner.

Colonel Jordan looked at the great impersonator with a grim satisfaction.

"It's taken a long time, von Zenden, but you're through now. I'm going to keep you in double irons, with four guards, until they stand you up before the firing squad."

Von Zenden coolly smiled.

"Thank you for the compliment, colonel, but—"

The door burst open and Beeding came into the room.

"Just returned, colonel," he panted. "Ah! So you've got Strange! Well, I've the goods on him this time!"

"You're crazy," snorted the G-2 chief. "Von Zenden's the man back of all this."

Beeding looked at the Prussian in amazement.

"B-but Strange—he broke out of the guardhouse—" he stuttered.

"Broke out?" said Strange, in a tone of astonishment. "Why, you released me, colonel, to work on this affair. Don't you remember?"

Beeding's jaw dropped.

"I—I released you?" he gasped. "You're mad!"

"Holy smoke!" exclaimed Noisy Jay. "Maybe it was von Zenden made up as Beeding and trying to get Phil in bad!"

Strange saw Colonel de Soucy's shrewd eyes shift toward Dornay, but Andre was speaking, and no one else noticed.

"No," said the little major, "von Zenden was at Dornay's place and— Mon Dieu! I have it! The man who released Strange must have been the real Monsieur Ie Diable! He did it so Strange could clear him later of these things of which he was accused."

He faced the Prussian inquiringly, and Strange saw Dornay whiten. But von Zenden mockingly shook his bandaged head.

"You will not learn that from me. Major Andre. I am in sympathy with any man who steals guillotines."

"You think, perhaps," said de Soucy, "he may save you from the firing squad in return for your silence?"

The Prussian gave him an ironic smile.

"It will not be necessary. When I am ready to leave for Germany, I shall make the necessary arrangements myself."

Jordan turned a beet red.

"Noisy, call the guard and get that blasted Hun out of here!"

Noisy obeyed, and von Zenden was led away, still apparently undisturbed. Strange caught de Soucy's eye and held it.

"The real M. Diable saved the day, after all," he said. "Perhaps it's just as well he was never caught or identified."

There was a silence, then the French colonel nodded.

"I think you are right," he said.

The color slowly came back into Dornay's cheeks.

"But I thought," said Andre, "that you had a clue, mon colonel?"

A twinkle came into de Soucy's eyes.

"Eh bien," he said, "you know what my clues are like."