Suddenly the laughter came to a stop. The building in which the show was being held shook as though a violent thunderclap had rocked the earth. This loud detonation that broke upon their hearing, however, was only too familiar to all those army aviators. They understood its dread meaning.

The enemy had taken this opportunity to send over a squadron of raiding Fokkers to bomb the hangars of the French and American fliers at Bar-le-Duc!


CHAPTER XII
CLOWNS ON THE WING

Boom!

What followed that first heavy detonation was very much like a riot. The audience became frantic under the belief that it meant an attack on the town, and that the missiles would presently drop upon the roofs, working destruction to everything around.

It was the actors, however, who were the most exercised. One and all they understood what it meant to them. Their planes were in danger of being demolished! In some way the Teutons must have learned about the entertainment, and realized that almost every Allied pilot would want to attend it. They rightly guessed that for once the guard about the aviation field and numerous hangars where the dozens upon dozens of planes of every description were housed when not in use, would be unusually light. They had also taken advantage of the bright moonlight to make a bold sally over the French lines and reach this distant point undiscovered.

Boom! boom! boom!

Other crashing sounds announced that the enemy machines were busily at work. Each pilot pictured the entire camp under bombardment, with the utmost disaster overtaking the airplanes upon which General Petain was depending so much to serve as the "eyes" of his brave army.

There was a general and maddened rush. Every one wanted to get to the camp in the briefest possible space of time. There was no chance for the actors to change their clothes. They were glad enough of an opportunity to snatch up a heavy fur-lined coat, either their own or some other person's. With this to hide their ludicrous attire, and also give some needed warmth once they went aloft, they hastened to find a waiting car, which, when loaded to its capacity, would be sent like mad along the road to the aviation field.

It was one of the most amazing sights imaginable, to see those pilots, many of whom were world famous, thus garbed. It looked as though some asylum of freaks had opened its doors and allowed the inmates to escape to the highways and byways.

Only one thought possessed them all, which was to get to the hangars in the shortest possible time. When they arrived each anticipated seeking his particular plane. If that chanced to be out of commission, then commandeering any other, it mattered little whose, so long as they were able to go up, and give battle to the audacious Teuton pilots who had raided their camp at Bar-le-Duc.

"We've got to save our machines!" cried Tom. "Come on!"

"Right you are!" responded Jack.

Tom and Jack were with the rest who found some way to crowd aboard one of the waiting cars that were seized upon to carry the pilots to the field. As they went booming furiously along the road they could still hear those frightful explosions ahead, each one accompanied by a flash as of lightning. The reports were almost deafening.

Eager eyes were turned aloft. The moon shone, but it was difficult to make out so small an object as an airplane at a height of a mile or more without the use of searchlights, and even these were not very efficient on such a night.

Still, some of the pilots believed they could see several enemy planes swooping over at a lower level, possibly, they thought, on the lookout for the procession of cars bearing the aroused Allied aviators to the hangars.

Bang!

A bomb fell not fifty feet away from the car in which the two chums were seated. One of their companions received a trifling wound from the effect of the explosion of the TNT contents of the bomb, said to be the most powerful known for such uses, and handled by the engineers of all the armies, under different names.

If the design of the Boche who swooped down for the purpose of waylaying the cars carrying the French and American airmen was to rob the Allies of the services of a dozen eminent pilots all at once, it failed in execution.

At last the aviators arrived on the scene. It was lively enough, with bombs still bursting here and there. Already considerable damage had been done to some of the hangars.

The Allied pilots were "mad all the way through" at having been caught napping by the foe. They paid no attention to the danger that still hung over their heads, with the enemy's supply of explosives as yet unexhausted. While the dreadful detonations continued, sometimes exceedingly close by, the various pilots seized upon such mechanicians as they could.

One by one the planes rolled along the field and began to climb upward by way of the usual spiral staircase route, to give battle to the enemy, regardless of any superiority in numbers.

Jack was dismayed to discover that his plane was badly wrecked by one of the explosions. Indeed, it was afterwards found that he had to have a new machine, since the repairs necessary to put the old one into service again were too complicated to be done at the front.

Tom was more fortunate. His hangar had also suffered to some extent, but so far as could be seen in a hasty examination his plane was not injured in the least.

He too went up, burnt-corked face and all. There were clowns abroad that night who could give Tom many points in the game, so far as comical looks went, and still easily win the stakes. But all else was forgotten under the spur of the moment, save that each man was eager to get in touch with the Boche pilots who had almost spoiled their one great evening.

But no longer were those crashing detonations coming. This told the story only too well. The Germans had either exhausted their supply of bombs, or else they deemed discretion the better part of valor. They had evidently taken their departure before the first Allied pilot got up to the elevation they had been using in their bombardment.

Nothing could be seen of them, though had the Allied pilots been able to use their ears, which was impossible when their own motors were making such loud noises, they might have heard, in the distance and to the east, the telltale music of Teuton propellers beating the air in a rush for home ports.

A pursuit was organized, and several planes followed the retreating invaders over the entire distance to the front; but it was of no avail. The enemy planes had had too good a start, and were being pushed for all they were worth to get beyond the danger zone.

There had been several accidents at the Bar-le-Duc field, but none of them fatal. This was not at all surprising, considering the haste shown by the pilots to mount and engage the foemen.

Too, several of the planes besides Jack's had been damaged, a circumstance which brought about disaster before the aviator was able to leave the ground.

As the fliers came back one after another, filled with indignation and disappointed hopes, Jack stalked about, with his black face, yet laughed to see what comical pictures most of his fellow aviators made.

By degrees most of them began to realize that the joke was on them, and joined in greeting with noisy shouts each fresh arrival from above. The damage had not been so very serious after all, since most of the Teuton bombs had either failed to explode when aimed true, or else only dug enormous craters in the ground where it did not matter, sometimes even a quarter of a mile away from the hangars. Jack's machine, it was found, was the only one badly damaged.

From that time there was one subject on which American and French pilots were agreed. They must certainly repay their enemy rivals for this visitation. The honors could not continue to be all on one side.

So from that hour every Allied pilot who went far back of the German lines used his glasses diligently, in the endeavor to locate the secret aviation field of the Boche. This would naturally be camouflaged in the customary fashion, at which the Teutons had become almost as proficient as the French; but trust an airman to spy out the lodging place of his kind.

Step by step they learned which direction the enemy planes took in coming to the front, and retiring when through for the day. Thus in good time the hiding place was found. Great was the delight of the whole Lafayette Escadrille when this confidential news was passed about. And, later on, a party of Allied aviators paid a night visit to the German camp, and dropped several tons of high explosives from bombing planes, that were heavily guarded by the fighting Nieuports.

They had reason to believe from what they themselves saw, as well as through a secret report received from a French spy, that their aim had been remarkably fine; and that many times the amount of damage the Germans had done at Bar-le-Duc had been carried out on the reprisal sally.

After that it seemed as though the slate had been wiped clean. Their honor had been fully purged of the stain that had rested on it ever since that dreadful night when they were caught off their guard.

It turned out that the enemy had meant to start an action on the following day, and it had been hoped that the squadron of airmen might so cripple the French service that the advantage would be all on the side of the assailants.

Something happened, however, to balk the plans of the Crown Prince. Perhaps he had a reprimand from his august father and emperor for so recklessly sacrificing such vast numbers of his men in a fruitless assault against the stonewall defensive of the French army. It may also have been something else that called the attack off, but at any rate it failed of accomplishment.

The stagnation along the front continued; but all this while General Petain was making quiet though effective preparations, in order some day to strike a staggering blow, such as the French had before given, which would take the enemy by surprise, and push him still further back.

Jack was fretting because thus far he had seen so little of real action. Since his Nieuport had been sent away, and another had as yet failed to arrive for his use, he often bewailed his ill-luck. He even assured his chum the "green mould would be growing all over his person if something didn't soon come to pass to break the terrible monotony."

But every lane, however long, must have its turning; and Jack's hour struck at last.


CHAPTER XIII
MORE WORK IN PROSPECT

"Tom, sit down here on this bench, won't you? I want to have a little talk with you about some things that have bothered me a whole lot lately," said Jack, some days after the exciting experiences narrated in the two preceding chapters.

"I can give a pretty good guess what they are, Jack, since I see you staring hard at the slip of paper found attached to the toy balloon which drifted over our lines from somewhere back of the German front."

"Yes; I own up I do sit and look at that paper, Tom. If it could only talk I'd know who penned that warning, and my curiosity'd be satisfied for one thing. But try as hard as I may, I can't be certain whether it was Mrs. Neumann, or somebody else. But I wanted to speak to you about Bessie just now."

"What about her, Jack?" asked Tom, knowing how much his chum was concerned over the unknown fate of the pretty young girl they had met on the Atlantic liner, and who was apparently anything but happy in the charge of her legally appointed guardian, Carl Potzfeldt.

"There are several things she told me, half unwillingly, I admit, that I guess I haven't said anything about to you, Tom."

"Then she confided her secrets to you, eh?" half chuckled Tom; though he saw his chum was in anything but a humorous frame of mind. "I remember you told me she felt very bitter toward all Germans because she had lost her mother when the Lusitania went down."

"Yes. But this had to do with her guardian," Jack continued.

"Oh, I see! Mr. Potzfeldt, Jack? You haven't felt favorably disposed toward that gentleman at any time since first meeting him."

"Neither have you, Tom, to tell the truth!" declared the other quickly. "In fact, as I remember it, both of us were pretty much inclined to believe he was a paid spy of the German Government, working on some line of dark business over in America. Well, he had to clear out in a hurry, Bessie told me."

"Did the authorities get track of his scheming work, and was he in danger of being arrested for plotting against Uncle Sam's interests as a neutral?" Tom asked.

"It may have been that; but Bessie wasn't sure about it. In fact, she seemed inclined to believe her guardian had some secret, which was in danger of being exposed. An old friend of her mother's was interesting himself in the matter. Given time, he might have made it uncomfortable for Carl Potzfeldt; and so the gentleman cleared out between two days."

"Taking Bessie with him!"

"Yes. They made as if to go to Chicago, but instead hurried to New York. When he came aboard at the last call he kept to his cabin for a time, until we were well away from land. There has been considerable of mystery about his actions. Bessie is afraid of him, too. She even hinted that she believed he might have obtained control of her fortune and herself through fraud, and that this was in danger of being found out at the time he cut stick and ran."

"All this is interesting, Jack; but just when and how we're ever going to learn the truth about it I'm unable even to guess. It would be like hunting for a needle in a haystack to try to find Potzfeldt. He and his pretty little ward may be hundreds of miles away from here."

"Perhaps you're right, Tom," mused the other sadly, as he stared afar off toward the north. "I'd be glad of a chance to do something for that poor girl. She is to be greatly pitied, if she's wholly in the power of a man who wouldn't hesitate to do anything, if he saw a chance for gain ahead."

"Well, all you can do, Jack, is to live on and hope a lucky chance will bob up for you. But there's our captain beckoning to me. Perhaps another battle is on the carpet for to-morrow, and I'll be given a look-in again."

"Oh, if the lightning would only strike me too!" sighed Jack, enviously. "Please beg him to figure out something I can do, Tom. If it's only occupying a place aboard an observation plane or taking photographs of the Germans regrouping far back of the lines, I'd gladly welcome it. Anything but sitting here, when all the other pilots are at work."

Tom hurried to join the commander of the Lafayette Escadrille. He had taken a great fancy to the gallant man, and believed this feeling was in a measure returned. Jack continued to sit and mope. He really felt slighted to be left out when so much thrilling work was being done.

He had put away the well-thumbed scrap of paper with its mysterious lines of warning, for the time being Bessie and all her troubles passing from his mind. Jack was now full of his own affairs. He found himself growing a bit discontented because thus far he had been allowed to do so little for the cause, when his heart was full to overflowing with a desire to assist.

There were aviators going and coming all the time, and surely many of them did not excel him appreciably in talents. Why did not those in charge find something for an ambitious pilot to do? He was striving daily to master the weak spots in his education; and had not the captain himself assured him he was doing bravely? He turned to cast an occasional look toward the spot where Tom and the commander of the air squadron still talked earnestly. Yes, something was certainly "on tap," as Jack expressed it, for he saw the other carefully examining a bit of paper his companion had evidently placed in his hand.

Jack began to be interested. Perhaps after all it might turn out to be something quite different from what Tom had anticipated. Had the captain simply wished to notify the other to be ready to answer a call on the following morning, surely he need not have taken all this time; nor would he have given Tom that paper, undoubtedly carrying explicit instructions.

How the minutes dragged! Jack thought it an eternity before he saw Tom and the captain separate. He was glad to notice that his chum once more headed in the direction of the spot where they had been seated on a bench back of the long row of frame buildings used for permanent hangars at the Bar-le-Duc aviation field.

Yes, Tom had evidently been told something that pleased him very much. His smile admitted the fact, and Jack knew by now just how to read the face of his comrade so as to get a good idea of what was passing in his mind.

"Looks like good news, Tom," he cried out, for motors were rattling and throbbing, mechanicians and helpers, as well as pilots, calling to one another, and all manner of sounds combining to make a great racket.

Tom shrugged his shoulders in a non-committal way, which might mean a whole lot, and again might express a small fraction of disappointment.

"Yes, I've been given a job, if that's what you mean," he admitted, as he dropped down once more on the bench alongside Jack, and threw one leg over the other.

"More fighting to-morrow, possibly?" queried Jack, anxiously. But he found his curiosity further whetted when Tom shook his head in the negative.

"Not necessarily this time, it seems," he went on to say; "though of course you never can tell what you'll strike when once you pass fifty miles, more or less, behind the enemy front."

Jack pursed his lips up as if about to whistle, but he made no sound. It was only a visible indication of surprise on his part–surprise, and an eager desire to know just what his chum was so slow in telling him.

"Another bombing raid, then, is it?"

"Never a bomb going along this time," came the puzzling answer. "Nor is there going to be a big bunch of planes starting out. I'm to be the only pilot in the game this time, Jack."

"You're knocking me silly with that, Tom," protested the other young aviator. "I can see the twinkle in your eyes, as if you were holding something back, so as to tantalize me. Are you free to tell me what this business of yours it is the captain has just handed over to you?"

"Oh, surely, Jack. He told me I could take one fellow into my confidence, and no more. So I mean to tell you all about it."

Tom turned and cast a careful look around. They were not very close to any of the hangars, it happened; and none of the many helpers and attendants could possibly overhear what was said, with all that clatter constantly going on.

"I guess it's perfectly safe for me to talk here, Jack, and not give the thing away. You know it does seem that the German spies are able to penetrate nearly everywhere, and pick up all sorts of valuable information, to send across the line in any one of a dozen different ways."

"Yes. But go on, Tom."

"It seems there is need of some one to go to-night to a particular place far back of the German lines–in fact, close to the fortified city of Metz itself. In a certain place, inside a hollow post, will be found a paper marked in cipher, and containing much valuable information which has been collected by one of the ablest of the French spies. He is really a native of Alsace-Lorraine, and well thought of by the Germans. As it is utterly out of the question for him to report in person, he has adopted this way of getting his news to General Petain. And as there is a scarcity of pilots capable of doing this work our captain has selected me to undertake it for the cause."

"But Tom, I should have thought he would have picked out some one more familiar with the ground back there. How can you find your way to that particular place, if you've never been there before?"

"I've been given directions that are bound to take me right," Tom assured his worried chum. "There was a man they used for this purpose, and several times he's brought back the papers; but on his last trip he had the misfortune to run into a bunch of cruising Fokkers, and they brought him down. He fell fortunately inside the French lines, so his papers were saved; but Francois will never handle the controls of a plane again. He was killed."

"Then there is danger in the game!"

"Certainly there is. But in these times who could dream of passing so far back of the German front without expecting to be in constant peril? The papers will be put in a little box previously prepared. Should disaster overtake us, it will be flung overboard, and before it reaches the ground everything will have been consumed by the fire that follows."

Jack's eyes began to glitter.

"Just so, Tom! But I notice that you used the plural pronoun when you spoke. Then you do not go on this mission alone?"

"No, that's right. I have been given permission to pick out my one companion, for there will be two of us aboard the plane to-night."

Jack tried to keep calm, but it was indeed difficult, and his voice faltered more or less as he hurriedly went on to say:

"Have you already made your selection?"

"Yes," the other assured him in his tantalizing way. "I wanted to know whether the captain approved of my choice; which I am glad to say turned out to be the case."

Jack gulped something down, and then blurted out:

"Did you mention my name at all, Tom?"

"Yours was the only one I had in mind; and Jack, rest easy, you're going along with me to-night to glimpse the lights of Metz!"


CHAPTER XIV
OFF ON A DARING MISSION

The two air service boys fell to talking earnestly concerning what they should take with them, and how to study a map which their captain had promised to put in Tom's hands immediately.

This was not of the ordinary kind, but so definitely marked for just such an emergency that even a novice could probably find his way to Metz, granting that he possessed the necessary qualifications of an air pilot.

Presently a messenger came with a package for Tom. This proved to be the chart from the commander of the air squadron. Tom was to make as good a copy as was in his power, for the original was too valuable to risk losing.

Jack understood that there were several reasons for having Tom do this. In the first place his work on the chart would familiarize the young aviator with its every detail, and fix things firmly in his mind. Then again, if they were lost, and never returned, the priceless chart for night voyaging over the enemy's lines would be at least safe.

Daring men had gone forth on similar desperate errands before then, and had never been heard from again. It is the fortune of war. Those who indulge in enterprises that border on the sensational must always expect to sup with deadly peril.

When the evening meal was announced the two chums were already deep in the work. Of course not a whisper of their intended mission was breathed at the table. No one dreamed of their contemplated trip. The customary chatter and good-natured badinage flowed during the whole supper-time. While some of the American aviators had received wounds in recent engagements there had been no chair vacant for some little time now; and hence no gloom rested on the escadrille. From the table the boys again went to their room.

"How far is Metz from Verdun?" asked Jack, as they labored to complete their preparations for departure.

"Not over forty miles, I should say, as the crow flies, Jack. I've never been over the route, but it can be measured on this copy of the map."

"And that's the direct line we expect to cover, of course?"

"We'll head due east."

"And as it'll be densely dark when we start I guess we needn't mount to ten thousand feet to pass over the enemy lines, eh, Tom?"

"There'll really be little need," came the reply, showing that the pilot had already figured all this out. "At the same time we ought to keep far enough out of range to avoid being struck by stray shrapnel."

"Will they bombard us, do you think?" demanded Jack.

"Oh, that's to be expected," said Tom indifferently. "You see the men who man the anti-aircraft guns are constantly on the alert. They're bound to hear the whirr of our propeller as we pass over, no matter how high we soar. The searchlight will spot us out, and then they'll do their best to make things uncomfortable for the pair of us. But the chances are ten thousand to one against our being hit."

"You said our course would be due east, didn't you?"

"I'll change that assertion a bit, Jack; we start east after we're well across the front, and away from the dazzling searchlight business. In the beginning we'll point the nose of our big machine toward the north."

"So as to deceive the watchers, of course," remarked Jack.

"That's what the game is."

Jack's eyes sparkled. He was always proud of his chum's clever reasoning powers, and believed Tom could hold his own with any one with regard to mapping out a promising plan.

Their preparations completed, the two air service boys lay down to secure a little rest. As they were not to start until some time after midnight, Tom believed they should secure a few hours of sleep. The moon was a late one, and would not rise, even with a midnight start, until they were well back of the enemy lines.

An alarm-clock aroused them at the appointed time. Tom immediately shoved the noisy thing under his blankets before it could wake up the entire house, and set people wondering what was happening that any one should want to be aroused at such an unseemly hour.

It was terribly black outside. Jack pressed his nose against the window and took a look, even while hurriedly finishing his dressing. Tom had taken the precaution to put a fresh battery in his little hand electric torch, which he believed would prove to be worth its weight in gold.

Arriving at their destination, the boys quickly found their two-seater aircraft awaiting their coming. Quite a crowd stood around, and made guesses concerning the possible reason for the captain's order that this plane should be made ready for a journey, with enough supplies of gasolene and oil aboard to cover any ordinary emergency.

Tom took no chances. He believed the attendants had faithfully carried out all directions, but to make doubly sure he looked over things himself. It was his life and Jack's that were at stake, and not those of the attendants; so he persisted in testing this and that thing until he felt certain everything was as it should be.

"Is it time we started, Tom?" asked his companion, when this procedure had resulted satisfactorily.

"We'll wait just ten minutes more," he was told. "I've figured everything down to a fraction, and expect to proceed by clock-work. We want to be well over the line before the moon peeps up. After that we can loaf a bit, and let the old lady get a little way above the horizon. That's so we may have the benefit of her light when we want to land."

The minutes passed slowly. Meanwhile the crowd increased, every man who chanced to be abroad at that hour of the night gathering to see the two Americans start on their mysterious errand. All sorts of guesses were indulged in, many of them of the wildest character. Jack hearing some of this talk, which he half understood, was convulsed in silent laughter over the remarkable ideas that seemed to possess the minds of those French mechanicians and hostlers.

Finally Tom stood up.

"It's time!" he said simply, and Jack understood without any further explanation. He at once proceeded to climb into his seat and complete his simple preparations for the work in hand, being already fully dressed in his fur-lined garments, and with his warm hood and goggles in place.

A minute afterwards Tom called out the word that started the propellers whirling. The motor took up the refrain, and hummed merrily, as though glad to be busy again. Then they were pushed along for a start, gathering momentum so quickly that the mechanicians dropped back to watch the dark object vanish almost wholly from their sight along the level field.

Both boys noticed the great difference between this two-seater and their own active little Nieuports. How clumsy this machine was, and how slow to answer to the call of the pilot! Yet it would be far better for their purpose than two of the small aircraft, since it allowed them to be together.

The few lights of the aviation field near Bar-le-Duc had faded almost entirely out of sight by the time Tom turned to the north and headed for Verdun. True, he might have pointed the nose of the airplane directly east, and saved considerable distance, but there were good reasons for not doing this.

To cross the German lines further south would surely convince the Teutons that the aviators were heading for the vicinity of Metz, which was just what Tom did not wish to have happen. Then again, his chart covered only the direct line between Verdun and the fortified city of Lorraine that forty-odd years back had been French territory, before the Germans seized it as spoils after the war that made France a republic for the third time.


CHAPTER XV
THE MOONLIGHT FLIGHT

The time for talking had passed. With the motor working noisily, and the twin propellers churning the air, they could hardly have heard the discharge of one of the 'Big Berthas', as the Allies were wont to call the monster Krupp guns, and so called them because a woman whose maiden name had been Bertha Krupp, owned a big interest in the works where they were manufactured.

All was dark around and below them. Above the stars shone, and gave a small amount of cold, cheery light. Tom had made a study of the heavens, and was able to steer by means of the stars. The aviator is often as much dependent on compass and heavenly bodies to shape his course as the sailor hundreds of miles away from land.

Tom was in no especial hurry. He had carefully thought out his plans, and meant to pass over Verdun at just a certain time. Then would come the two lines of hostile trenches, and the ordeal of searchlights and shrapnel. Once that was done with, they had really little further to fear.

The minutes slipped away. Under ordinary conditions they were accustomed to making that thirty miles in just about half that number of minutes, thanks to the ability of the speedy Nieuports to cover distance. It would be twice that now before they would find themselves at the front.

Already they could see various signs to tell them they were drawing near. Rockets used as signals of various kinds ascended at intervals, and burst. Others of the star variety, and which discharged glowing white electric balls that lighted the earth below, could also be seen. One side or the other apparently had some reason for desiring to scrutinize a special sector of terrain in No-Man's-Land, the disputed region lying between the hostile trenches.

Jack used his eyes to advantage. These things had not yet grown stale with him, for he still found himself filled with awe and wonder when gazing down from a lofty height at the world shrouded in darkness below.

There within a comparatively short distance, that might not be over twenty miles, a round million of soldiers were gathered, armed with numberless engines of destruction of the most ponderous nature imaginable. It was enough to give any one a genuine thrill, and Jack felt such a sensation creeping over him.

The crucial time had now come. They were passing over the line of the French trenches. Jack knew this from various signs, and also that in another minute they might expect to be spotted by some of the enemy searchlights. These would be unmasked, and trained on the heavens in the effort to locate the cause of that well known clattering noise above.

This speedily came about. First one long shaft of dazzling light rushed back and forth; then others joined in the hunt, until presently they focussed on the progressing two-seater pushing north.

Then began the bombardment. Numerous anti-aircraft guns were poking their noses upward in anticipation of just such a call. Their crews commenced to shower the shrapnel around and below the bird of passage, whose mission, whatever it might prove to be, could mean only evil to the Teuton cause.

All this racket was lost upon the two so far above the earth. They heard nothing of the bleat of the firing guns. Even the bursting of shrapnel went unheeded, save at a time when a shell exploded close by, and was faintly heard.

Tom was wisely taking but little chance. He maintained an altitude that prevented most of the shrapnel from coming anywhere near the plane.

They crossed the enemy front, and sped on. The bombardment diminished in fury as they left the first and second line trenches behind them. It was continued to some extent from an elevation further back, but as Tom knew of this formation, and had crept up still higher, no accident happened to them.

At last the air service boys were fully launched on their night voyage through the upper currents. Tom waited until he considered that it was really safe to change their course. He did not want to betray his movements in case some daring Boche pilot started up in a swift Fokker machine to pursue them.

Once he shut off the engines and volplaned down a thousand feet or more. This was done because it was intensely cold up where they were; and the reasons that had kept them at such a high altitude existed no longer. Then again Tom wished to listen to discover if there was another aircraft near them; and this could be done only when his motor was silent.

"No pursuit, Jack!" he managed to call to his chum before they once more straightened out, and again allowed the motor to send forth its loud hum.

Jack had no chance to make any sort of reply. It did not matter, for he, too, had eagerly listened, and had failed to catch any telltale sound.

Immediately Tom shaped a new course. No longer were they heading toward the north by east, but directly east. There some forty miles, more or less, away, lay the city of Metz, the object of their mission.

After moving along in this fashion for a short time Tom drove his machine more slowly. He was watching for the rising of the old moon ahead, where the horizon was already lighted with her near approach.

How strange she looked peering above the edge of the world as though curious to see all that was going on in this troubled hemisphere. Jack thought he had never witnessed a more peculiar spectacle. But at least this fragment of a moon would be likely to afford them the necessary illumination required when they attempted to land in a field that neither of them had ever seen before, and only knew through information imparted by means of their chart, and its accompanying notes.

Some other pilot had doubtless been over this same route on previous occasions; yes, and even landed in that identical field. He had made the chart; and the accompanying memoranda consisted of his personal experiences.

Already the moon had dispelled some of the cheerless gloom round about them. It was still cold up in that upper strata of rarefied air; but their fur-lined garments kept them from suffering. Besides this, they were young and vigorous, and their blood was warm, and they were excited with their mission and able to ignore any physical discomfort that might come to them.

Jack continued to stare ahead as time passed. He was looking for some sign of the city towards which they were flying. Tom, on his part, often took note of his compass, then flashed a glance up at the stars, and finally sought to discover some landmark far down below that was marked upon the chart.

He had the utmost confidence in his own judgment, and believed he would bring up at the identical place which was their goal.

Tom now volplaned again, wishing to draw nearer to the earth. It was while thus dropping, with engine muffled, that his ears caught a sound calculated to give him an uneasy feeling.

This was undoubtedly the whirr of a propeller beating the air in furious fashion. It also came from behind. Jack, too, had caught the sound, and was thrilled with sudden apprehension of impending trouble.

They were undoubtedly being pursued, and by a much faster plane than their own. This would mean that presently they would be overtaken and fired upon. It was not in the nature of Tom Raymond to allow such a thing to occur and be kept from doing his share of the fighting.

When Tom swung around to face the rear, and actually started to run toward the oncoming foe, Jack knew what was expected of him. He must man the gun, and prove how well he had learned his lesson when at school at Pau and at Casso.

No longer could they expect to be guided by sounds. Their own motor thundered so loudly that every other sound was deadened. They must depend on eyesight alone to tell them when they were nearing the oncoming Fokker craft. Perhaps the first indication they would have of its presence would be the flash of its quick-firing gun, spattering bullets around them like hail.

So Jack strained his vision to the limit. He was eager to discover the enemy before they themselves were seen. Much might depend on who fired first, in a duel of this kind.

Suddenly the gun began to bark after its own peculiar way. Jack believed he had glimpsed something moving, and was sending forth a storm of lead in the hope of a lucky hit that would crumple the other machine up and put an end to that peril.

Tom held the course. He knew that every second was carrying the rival airplanes nearer together–knew that possibly they were so headed that if they continued to rush forward they might smash in a frightful collision that would send both down thousands of feet to the earth.

It was a time for careful calculations and prompt action. Tom gripped the controls and was ready either to swerve or to dip as occasion demanded. Meanwhile, Jack was doing his best to riddle the advancing Boche machine and its pilot.

There was no longer any difficulty in seeing just where the Fokker was, for a constant flashing as her gun rattled betrayed its position exactly. The flying lead was now whistling all about the two air service boys but they did not know how close they sailed to death.

Then Tom swung smartly to the right. He dared not keep on longer in his course lest he collide with the German craft. Just about the same instant he realized that the Fokker was diving. There was something queer about that manoeuvre. Tom had never known a French or an American nor yet a British airman to adopt such a clumsy way of plunging so as to avoid punishment.

Circling around he started back on a little lower level, looking for the enemy. In making his latest volplane Tom had listened intently, hoping to ascertain whether the motor of the enemy craft still throbbed somewhere close by; but he heard not a sound to tell the story.

Just then, suspicious of the truth, he glanced down, and was just in time to see a little flash of flame arise from the distant surface of the earth. Then the awful truth broke upon both boys. They realized that the German pilot had lost control of his machine, which had turned over and over in its drop, finally crashing to the ground, and being instantly enveloped in flames!


CHAPTER XVI
LANDING CLOSE TO METZ

Tom had his hands full in trying to get back to his course again. Naturally, in the excitement attending the duel in midair he could not pay attention to where he was going. It was easy enough to shape his line of flight by the aid of the stars and his compass, but he had also to catch certain landmarks below, that would serve to guide him.

Fortune favored him in that he quickly sighted the lights of a town; and this gave him the bearings he sought. His mind freed from further anxiety concerning this matter, he pushed on once more.

When presently he became aware of the presence of more lights Jack gave Tom the signal agreed on between them to mark such a circumstance. Then the pilot again commenced to drop to lower levels by a series of easy volplanes.

Like a huge bird the airplane swept along, now close to earth. Had one of the peasants who lived in that region chanced to be aroused by the rattle of the propeller and thrust his head out of his cottage door, he must have gazed in awe to see the vast shadowy form come between him and the starry heavens, with the light of the moon silvering its extended wings.

One trip failed to show them just what they wanted, and so Tom, knowing that the field must be somewhere in that immediate neighborhood, immediately swung around and started in again.

The second search failed to bring success. Jack began to experience a sensation akin to dismay. Was their work doomed to meet with no result and would they find themselves compelled to start back to Verdun without having accomplished the important errand on which they had been dispatched?

It was not Tom Raymond's way to feel discouraged because things did not always go as he wished from the start. He believed in the old motto, "If at first you don't succeed, try, try again." And he would circle around that vicinity for a full hour if only in the end he might find that for which he searched.

Three times however, was the limit. Then Tom felt certain he had "struck pay dirt"; and that the opening lying below was the identical field to which he had been directed.

After that it resolved itself into a simple landing by moonlight. There were no ready mechanicians waiting to lend a hand; and everything must be done by the pilot and his assistant. But then, all war aviators must be able to make ordinary repairs if necessary, and do other duties that usually they allow the mechanics to perform.

Tom brought the heavy machine to the earth softly. It was fine work he did, considering the fact that it was unfamiliar ground he was striking and the moonlight was far from strong.

They jolted along a short distance, and then came to a full stop. Jack was the first to spring out. His first thought was of the strangeness of being on German soil, far back of the fighting lines, and within a few miles of Metz, a city of prime importance.

Hardly had they landed when the air service boys found themselves listening to sounds that seemed significant. Plainly came reports of firearms and of loud shouting, as of excited men.

"What do you think that row means, Tom?" asked Jack, as they stood listening with quickened hearts.

"It's hard to say," the other replied. "They may be having a riot of some kind over in the city. But I'm afraid it is more apt to have something to do with our presence here."

"Do you mean they've seen our dropping down and that there may be soldiers on the way here to see what we're up to?" asked Jack.

"That may turn out to be the truth of it. But we mustn't lose any more time. What we want now is that paper. Jack, remember that we arranged it so you'd stay with the plane, while I hurried off to get it."

"All right, Tom; only I wish you'd let me go along. Then if anything happened we'd be together, anyhow."

"It's better for you to stay here. I'll be gone only a few minutes if everything turns out O.K."

Tom turned and ran across the field. Jack stared after him until he lost track of the runner in the misty moonlight. Then he occupied himself in listening to that clamor and wondering whether it was really getting closer, or if his fears only made him think so.

There was certainly a big noise. Men continued to shout, and guns were being discharged, but not so frequently as before. Perhaps this latter was done by nervous guardians of the Lorraine city, who on first hearing the racket took it for granted that it meant an airplane attack, and were therefore starting in to bombard the skies, discovering hostile fliers in every lurking fleecy cloud.

Yes, Jack was positive now that those who shouted to one another must be coming out of the city, and heading for the big field where Tom had dropped down.

"Like as not," Jack told himself, "some wisebody has discovered that airplanes have been using this ground for alighting. When they had word that an enemy machine was heading this way they just naturally concluded it might drop down here. I guess our little fight up aloft was heard and understood by some one on guard. I hope Tom will soon get back here, that's what!"

Tom had been gone several minutes, and Jack tried to pierce the misty light beyond in the endeavor to discover some sign of his returning. His uneasiness increased, and with reason, for the noise was drawing perilously near.

Jack tried to figure out what his plan of campaign should be in case a motley mob of citizens and soldiers suddenly appeared in view, carrying lanterns, and perhaps blazing torches.

True, he had his automatic pistol with him, but what would that puny weapon avail when pitted against a score or two of enemies; many of them armed soldiers of the Kaiser, who would ruthlessly fill him with lead at the first show of resistance on his part?

Would it be better policy for him to slip away and conceal himself in case they did arrive before Tom returned?

But had not Tom explicitly told him to stay on guard over the airplane until he came back? Jack drew in a fresh breath. He threw back his shoulders aggressively and his mind was made up. He would stick it out, no matter at what cost. If the Boches wanted that plane they would have to fight for it, that was all.

He had his pistol out now, and was fondling it as a child would a pet toy. So far Jack had fired the weapon only at targets, but he had the reputation of being a good shot. He believed he could make every bullet it contained tell.

Then what about the mitrailleuse aboard the plane? Was it not possible to train it on the advancing host, and give them such a hot reception that they would break and race madly for shelter?

He knew the gun was fixed to shoot straight ahead. This was the custom with all those who went up in airplanes. To attempt to fire any other way would imperil the stability of the plane, and in many cases bring about sudden disaster.

Jack fumbled for the fastenings of the airplane mitrailleuse, it being his intention to swing the gun free, so that he could turn its muzzle in any quarter desired. But it had been too well secured in place for such a quick delivery, and presently he gave the idea up as a bad one.

No Tom yet! Things certainly were taking on a dark hue, and it looked as though desperate trouble might be in store for the two chums. Jack almost believed he could see dancing lights coming along what might be a road. He looked again, and no longer had any doubt on that score.

"Well, a fellow can die only once, and after all what does it matter whether he meets his end by falling ten thousand feet from the clouds or in trying to hold off an angry mob of Teuton soldiers and citizens of Metz who are in sympathy with the methods of the Kaiser?" Jack's reflections served to give him courage.

There was the leading one of the mob, starting across the dimly lighted field! Jack set his jaws hard, and determined that he would wait until the other had come close up. Ammunition was much too precious to be wasted without results following.

He was soon glad he had made such a sensible resolution, for as the runner drew closer something familiar about his figure and methods of leaping told Jack it was none other than Tom.

"Get aboard in a hurry, after you've given the propellers a swing!" cried Tom, almost breathless himself after such a sharp run. "I've got what I wanted."

He was already in his place with his hand on the control.

"Tell me when, Tom!" sang out Jack.

"Cut loose!" ordered the pilot.

The propellers spun, and the motors commenced their furious throbbing. Jack swung aboard, and at once the plane started to roll along the field, even as men appeared, bursting into view on one side, and shouting harshly as they realized how close they had come to catching those they sought.


CHAPTER XVII
MORE TROUBLE FOR THE CHUMS

It had been a close call for the two air service boys. Had they been delayed just a minute or two longer escape might have been impossible. And to have been caught with the spy's paper of information in their possession might have proved a very serious matter.

Some of the mob, that had come from Metz itself, were German soldiers. They carried guns with which they opened a hot fire on the departing plane.

Again the lucky star of Tom and Jack seemed to be in the ascendant, for they did not receive even a scratch. Later they found reason to believe that a number of the leaden missiles had come very close to their persons; for the marks upon the body of the plane itself, as well as the tiny holes in the stout linen covering of the wings, told where bullets had passed. Possibly, though, these had come from the rapid-fire gun handled by the Boche airman.

The plane had left the ground and started to mount when this shooting occurred, so that the marksmen had at least had a fair target at which to fire. But as the departing airplane was speeding away from them the rapidly increasing distance may have disconcerted the Germans. At any rate they failed to bag their game.

The boys were now mounting upwards again, filled with joy over their recent escape. Jack felt sure that Tom had the precious paper; for he well knew the other would never have returned so quickly had not success rewarded his search.

They were soon heading directly for their distant base. Tom could now give his aerial steed the rein, and get all the speed possible out of the cumbersome two-seater. There was no longer any necessity for "loafing on the job," to allow a tardy moon to come in sight, as had been the case before. Home, and at top speed, was the slogan now.

But, alas! it was not long before Tom realized that something was wrong with the plane. He found it increasingly difficult to manage the engine, and the machine began to give erratic jumps that alarmed Jack.

Had it been possible to make himself heard above the clatter of the motor and the propeller, Jack would have been much inclined to shout out, and ask his more experienced comrade what had happened.

Still he could give a shrewd guess. One of the bullets fired by the Teuton soldiers must have struck some part of the motor, and done enough damage to make its workings exceedingly erratic. If such were the case, would it be wise for them to try to push on at this high altitude, where a sudden collapse would mean death for both of the occupants of the disabled plane?

Tom soon shut the motor off, and tilted the machine for a volplane down several thousand feet to a new level.

Jack held his breath. This was partly because the wind rushed at him in a vicious fashion while they were plunging downward, and also on account of a new fear that clutched his heart.

How about the wings of the airplane standing the strain when Tom suddenly brought that volplane to a stop and tried to sail on an even keel again? Would they hold out? Or had some defect occurred in them which could also be charged to the spattering bullets fired by the Metz mob?

Then Jack breathed easier again.

The thing had been accomplished, and they were once more speeding onward, as Tom touched the controls that started the motor working. All then was well, as far as they had gone. Apparently they could by successive stages descend close to the treetops, and skim along until some favorable open space showed, into which a skillful pilot would find it possible to drop lightly and land.

A second volplane further added to Jack's peace of mind. They were now halfway down, and all seemed well. The earth loomed up below, although as yet it took on only a vague, misty effect, due to the weak moonlight.

Jack busied himself in trying to make things out, as for the third time the nose of the heavy observation Caudron was suddenly pointed downward, and they took the next "header."

This time Tom dropped a greater distance. When once more the loud hum of motor and propellers was heard they had almost reached the treetops. Jack gave one gulp, in fear lest his pilot could not make things work as he intended, and that they must crash to the earth while descending at such frightful speed.

Now everything was all right. They could not be more than a thousand feet above the floor of the valley they were following in their homeward route. If anything happened surely Tom would find some way of making a landing, even if a clumsy one that would put their machine out of the running and leave them stranded on enemy soil.

They continued to move along slowly, both looking eagerly to discover signs that would invite a possible landing. It looked as though they were in the country; at least they did not discover any signs of lights to indicate the presence of houses near by.

Soon a landing proved feasible, as they came to just the kind of open plot the air service boys yearned to discover. To make absolutely certain before committing himself, Tom circled the ground twice, and even dropped lower and lower while so doing, all the while straining his vision to the utmost.

Then the thing was done.

That was far from a pleasant landing. It shook them up considerably; but Jack was of the opinion that no damage resulted to the airplane, which after all was just then the main consideration.

Both of them leaped to the ground, after which Tom secured his electric hand-torch which he had found useful so many times while on the outward trip and he wished to consult the compass or the register of the barograph.

"I guess there's some sort of a house near by," said Jack, "because a rooster crowed over yonder. Yes, I can see what looks like the line of a road, too. I suppose it runs the entire length of this valley."

While Jack was saying this softly the pilot had started to take an inventory of the motor. His now practiced eye ran along this and that part, each of which was so essential to the smooth running of the engine. Tom too had already formed a pretty clear idea as to where he was likely to find the damage, and hence was able in a short time to give a satisfied grunt.

"Located the trouble, have you, Tom?" queried the other.

"Yes. It's right where I expected to find it. A bullet has made a dent that interferes with the free action of the part. Besides, I think that spark plug has become fouled with oil, and will have to be changed to get the best results."

"How lucky you brought another with you! Lots of fellows wouldn't have bothered about such a little thing."

"I had my suspicions about that when we started," explained the other, "even though the mechanician assured me it was perfectly clean. I know different now, and will certainly give him a piece of my mind when we get back."

"Then you expect to get home safely, do you?" asked Jack, in a relieved tone, that proved how anxious he had been growing since troubles had so consecutively alighted on them.

"Surely," chuckled the other, with his usual confidence in voice and manner, "a thing like this isn't going to stop our plans. Here in this retired spot nobody's apt to bother us while we make our repairs. You can hold this torch, Jack, and shove the light squarely on the work."

Tom worked for some time. He tapped as gently as possible when knocking out the dent made by the bullet, and he gradually removed the cause of the trouble. He was just finishing with the spark-plug when the confidence of the air service boys received a sudden jolt.


CHAPTER XVIII
THE LONE HOUSE BY THE ROADSIDE

"Listen, Tom!" hissed Jack.

The other had just sighed with relief on completing the work of replacing the spark-plug that had become fouled with oil.

"I, too, heard it plainly, Jack!" he breathed.

"Was it someone screaming or sobbing?" asked the other breathlessly.

"Sounded like it to me."

"And either a woman or a girl, at that!" hazarded his chum in bewilderment.

"It might have been a boy," suggested Tom. "There it is again."

Both of them listened. Peculiar sensations crept over them as they stood and thus strained their ears to catch any further sounds. Sobbing at any time is enough to arouse the feelings of a sensitive nature; but heard in the dead of night, and under the conditions that surrounded the two young aviators, made it all the more thrilling.

Jack in particular was touched to the heart.

"Say, that's a queer thing, Tom!" he muttered. "Why should anybody be crying or screaming like that away off here, and at this time of night?"

"Oh, there are many who are weeping in these dark days," said Tom gravely. "The men in myriads of families will never come home again. Perhaps a mother, or it may be a sister, has just had word that son, father, or brother has been shot down in battle."

Jack shuddered. Why should his thoughts instantly fly to the Boche pilot whom they had met and fought and conquered while on the way to Metz on their present perilous mission? It had been a fair fight, and a case of their lives or his. Nevertheless Jack shuddered as he remembered how the other had gone down after that last exchange of gunfire.

"Tom, notice that it comes from almost the identical direction where I told you I heard the crowing of a rooster a while ago," he hastened to say, more to rid his mind of those ghastly thoughts than anything else.

What a strange fatality if this should be the home of the unfortunate Teuton pilot of that Fokker machine, and the one who mourned was his mother or a young sister, or perhaps his wife!

"That means there's a house not far away, possibly an estate of some kind," mused Tom, as though turning over some sudden project in his mind.

Jack guessed what his chum was thinking about.

"Tom," he said softly, when for the third time they caught the heart-rending, half stifled sobs coming on the still night air.

"What do you want now, Jack?"

"I was just wondering whether you'd agree to something," continued the other, in a persuasive tone. "We're not in any great hurry, are we?"

"Well, no, perhaps not, Jack; though I'd like to deliver the paper into the hands of our commander as soon as possible. It is probably of the utmost importance, you know."

"I can't help thinking how I'd feel, Tom, if my mother or sister were in some great trouble, and fellows who might be in a position to hold out a helping hand considered their own personal safety first."

When Jack said this his voice was husky. Apparently the incident appealed strongly to his emotions. Jack had always been unusually thoughtful in regard to women of whatever age or degree, and would go far out of his way to do one a favor; so it was not strange that he should feel as he did at this time.

Tom was in a mood to be easily persuaded. The plaintive sobs, telling of woe that clutched some one's heart-strings, stirred a responsive chord within him. He, too, remembered those at home. Jack had put a clincher on his argument when he asked what their opinion of a man would be who turned aside and went his own way after hearing a woman or a child crying bitterly.

"All right, then, Jack; perhaps we can spare the time to take a turn around here, and see if we can be of any help," he announced, greatly to the satisfaction of his chum.

"Perhaps some one has been hurt and needs assistance," suggested Jack. "It isn't going to delay us much, and may be of great help to them. Come on–let's be on the move."

Tom was not quite so precipitate as his companion. Caution had a part in his make-up.

"Don't try to rush things, Jack," he said. "I must take a last look over my work here, you know."

"But you said everything was completed, Tom!" persisted the other.

"So it is, but I ought to make doubly sure before we leave the plane," Tom added, as he took the electric hand-torch from his companion and began systematically to look over the engine at which he had been working, carefully examining every detail.

Jack said nothing further. He understood what his chum meant when he declared it important that they should know absolutely the motor was in prime condition for immediate service. Something might occur to necessitate a hurried departure from the vicinity; a detachment of the enemy forces might appear, or other perils hover over their heads that might be laughed at only if they could take to the air without detention.

Tom was not long in doing as he desired. Meanwhile Jack could hear an occasional sob from the same quarter as before, and the sounds continued to exercise a peculiar influence over him which he could not have explained had he been asked.

"I'm ready now, Jack!".

"Glad to hear it," muttered the other, half under his breath; not that he meant to infer Tom had been unduly long, but because his feelings were wrought up to a high pitch that caused him to quiver all over.

Tom evidently guessed this, judging from his next remark.

"Cool down, Jack," he said, laying a hand on his companion's arm. "This will never do, you know. Getting excited is the worst thing an air pilot can do. It'll prove fatal to all your hopes, unless you manage to control your feelings better."

"I guess you're right, Tom."

"I don't think there's any chance the plane will be discovered here in the open field, even if there is a road so close by," mused the pilot, after they had gone perhaps as far as twenty-five yards.

"Not in a thousand years," asserted Jack confidently, turning to look back as he spoke. "Why, even now I can't discover a sign of the wings, or anything else in the misty moonlight, it's so deceptive. Only that lone tree standing close to where we dropped tells me the location of our plane."

"Yes, I marked that, too," asserted Tom quietly. "I thought we ought to have some sort of landmark to guide us if we should be in a hurry coming back. And the tree, standing up fairly high, can be seen ten times better than anything close to the earth."

"Here's the road, Tom."

"So it is, and an important one in the bargain, judging from its condition," remarked the other, softly.

"It runs the length of the valley, of course," added Jack. "I shouldn't be surprised if it went all the way from Metz to the Verdun front. If that's the case it must have considerable travel, even if nothing has chanced to come along since we landed."

"I can see signs to tell that we are close to some sort of country estate, or it may only be a Lorraine farm."

"I can glimpse lights through the trees, and chances are they come from windows in the house beyond."

"I see them too," affirmed Tom.

"But say, isn't it pretty late for a farmhouse to be lighted up like that?"

"Depend on it, there's some good reason for all that illumination," Jack was told. "And perhaps we'd better drop this talking so much, now we're getting close to the place. No telling what we'll find there. For all we know this may be some one's headquarters, though pretty far back of the line for that sort of thing. But I think it'll turn out to be something more than ordinary."

It did.

Jack began to weave all manner of fantastic explanations to account for the illumination of the house alongside the road to Metz.

He felt he would not be very much astonished to discover a line of military cars standing at the gate, and find that an important council of war was being conducted within the building.