"Tom, we've done it!" Jack shrieked, when he saw the enemy Gotha plane take a sudden significant dip and flutter downward like a stricken bird.

Evidently a shot more fortunate than any that had preceded it had struck a vital part of the rival craft, putting the motor suddenly out of repair.

When he felt his plane begin to crumple up under him the Hun pilot had commenced to strive frantically to recover control. Jack, horror-stricken by what was happening, leaned over and watched his struggle, which he knew was well nigh hopeless from the beginning.

Still the German ace made a valiant effort to avoid his fate. He could be seen working madly to keep from overturning, but apparently his hour had struck, for the last Jack saw of the beaten Gotha it was turning topsy-turvy, falling like a shooting star attracted to the earth by the law of gravitation.

That affair being over, Jack, breathing hard, now allowed himself to pay some attention to what was going on in other quarters. At the same time he proceeded to introduce a fresh belt of cartridges into the hungry maw of the machine gun, in case they were forced into another engagement.

Above them the battle still raged, though of course Jack could not decide which side might be getting the better of it. His interest focused chiefly on the bombing machines, which he found were now far away, moving along in erratic courses as their pilots strove to get in exact position for a successful blowing up of the bridge.

Jack could count only three of them. Unless the fourth had wandered far afield it looked as though disaster had overtaken its crew. No matter, even such a catastrophe must not deter those remaining from seeking by every means in their power to reach their objective.

Even as he stared downward Jack saw another of those brilliant flashes that proclaimed the bursting of a bomb. He felt a sense of chagrin steal over him, because so far no explosive seemed to have succeeded in attaining the great end sought. The bridge still stood intact, if deserted, for he could catch glimpses of it when the smoke clouds were drifted aside by the night breeze.

Fires were now burning in several quarters, started undoubtedly by some of the bombs that had missed their intended objective. These lighted up the scene and gave it a weird, almost terrifying aspect as witnessed from far above.

All at once Jack saw some bulky object pass between their machine and the ground below. It must be the missing bomber, he concluded, though the realization of the fact made him thrill all over in admiration of the nerve of those who could accept such terrible chances.

Yes, despairing of getting in a telling blow at such a height, the reckless crew of the big Yankee plane had actually dropped down until they could not be more than a thousand feet from the earth. And now they were speeding forward, meaning to test their skill at such close quarters.

Not being able to make Tom hear his voice, Jack gave the other a tug, and so managed to call his attention to what was passing below. Just in time did Tom look, for at that very moment there came another of those amazing brilliant illuminations, and the dull roar greeted their ears a few seconds afterwards.

They saw with staring eyes the air filled with the material that had once constituted the wonderful bridge, across which day and night the retreating Huns were taking their valuable guns and stores. A brief space of time did the scene bear the aspect of chaos, and then, when the smoke cleared sufficiently for them to see, they looked upon a void where the bridge had stood.

Jack fell back appalled, yet quivering with deepest satisfaction. Their raid would be one of triumph, since the main object had now been achieved.

Hardly had he allowed himself to exult after this fashion than Jack discovered that Tom seemed to be greatly agitated. So he once more looked down, filled with a sudden fear lest the gallant fighters in that adventurous bomber had paid dearly for their success.

He immediately saw that his alarm was not groundless. The big Yankee plane must have been struck in some vital part, for it was rapidly sinking as though doomed. Jack's only consolation lay in the fact that the crew seemed to be in better luck than those of the stricken Gotha; for they managed to keep from turning turtle; and unless striking the ground with too great violence might yet come out of the affair alive, even though finding themselves prisoners of war.

Tom was already striking for the upper levels. He saw that the other three bombers had also commenced to climb, since their mission was now carried out, and further risks would be only a needless hazard. Then, too, the crews of the battle Gothas, realizing that they had failed to save the bridge, concluded to withdraw from the combat, leaving the Americans to make their way back to their starting point, victorious and rejoicing.

Yes, there was the signal flashing from the plane of the commander, which meant that the raiding squadron should assemble above the reach of the crackling shrapnel, and prepare in a body for the homeward journey.

A sense of exultation, mingled with sincere thankfulness, gripped the hearts of the two Air Service Boys as they realized that the peril was now really a thing of the past. The homeward trip would be a mere bagatelle, for surely no Huns would venture to attack them while on the way. By exercising good judgment they ought also to keep above the reach of those elevated anti-aircraft guns along the front hills.

Now Jack remembered the temporary blinding sensation. He found on investigating that he had been near a serious accident, since a passing bullet had grazed his head, cutting the skin and causing quite a copious flow of blood.

"What's happened to you?" called out the alarmed Tom, on seeing that the other was binding his handkerchief about his head.

"Another scratch, that's all," replied Jack, as though that were only a matter of course, to be expected when modern knights of the upper air currents sallied forth bent on adventure. "A miss is as good as a mile, you know, Tom. And I guess I have a hard head in the bargain. It's all right, nothing to worry over. Fortunately it didn't strike me in the face, and mar my beauty any."

Jack could joke under almost any serious conditions; but Tom felt relieved to know the worst. They were at the time back again in their appointed place, tailing the procession.

Counting again as best he could, Jack discovered that there were only seven of the battleplanes in the double line now. It looked very much as though the loss of the big bomber was not the only penalty they had paid for their daring raid. But no doubt the story would all be told after the flight was over and the various pilots and observers could get together to compare notes.

Again were they subjected to a bombardment when they sailed over the German front lines; but this time, taking a lesson from their previous experience, they maintained such an altitude that no shrapnel was able to reach them.

Shortly afterward, and one by one, the battered Yankee planes dropped on the open field where the hangars lay, like huge buzzards alighting to satisfy their hunger in an orgy.

The first thing Tom did when he and Jack found themselves again on their feet and the waiting mechanics and hostlers looking after their plane, was to reach out and seize upon his chum's hand.

"We've got good reason to congratulate ourselves on coming through that nasty business so well, Jack," he said earnestly. "If you look at our machine you'll see how near we came a dozen times to cashing in our checks. They knocked us up pretty well, for a fact."

"I should say they did," admitted Jack, as he examined the various marks showing where the Hun bullets had punctured different parts of the wings, or struck the fuselage, narrowly missing both the motor and the partly protected petrol supply tank.

They lingered around for a full hour, there was so much to talk about as they gathered in groups and compared experiences, as well as commented on the possible fate of their fellow aviators who had failed to return.

In spite of the loss incurred, the achievement accomplished was of such a character as to fill them with pardonable pride. No member of that historical night raid, whereby the retreat of the Germans was so badly handicapped by the loss of the big bridge, would ever have cause to blush for his part in the bold undertaking.

Finally the two chums, finding themselves exhausted and in need of sleep, broke away from the chattering throng and sought their bunks in the former Hun dugout. All was now silence around them, the enemy batteries having ceased sending over even occasional shells; and they were able to enjoy a few hours of rest undisturbed by having the roof of their shelter damaged by a chance explosion.

On the following morning the advance was resumed, the same tactics being employed that had met with such success all through the Argonne. Wherever they discovered that machine-gun nests had been placed these were "mopped-up" by surrounding them, and then attacking from the rear, while the attention of the defenders of the stone house, or it might be a windmill foundation, was gripped by a pretense at frontal assault.

Those who had participated in the air raid on the bridge were given a day off, so as to recuperate. They felt that they deserved it, for the destruction of that bridge was apt to be a serious stumbling-block in the path of the retreating Huns, one that might cost them dearly in the way of prisoners and lost artillery.

Jack utilized this opportunity by striving to learn important facts in connection with the matter that was weighing so heavily on his mind. He absented himself from the dugout which the air pilots continued to occupy and which they disliked giving up until assured of some other half-way decent billet in a village that might be abandoned by Fritz when falling back.

Of course Jack had to have his slight wounds attended to, and in order to make sure that he had not neglected this before going off, Tom, during the morning, found it absolutely necessary to wander over to the field hospital, where of course he looked up Nellie.

Really it took almost a full hour for him to make all the inquiries he considered essential; and he might have consumed a still longer time but that there was a call for the nurse's services, and she had to excuse herself.

"Never mind," said Tom grimly to himself, as he made his way back to the old dugout, "it was well worth the walk. And Nellie is looking fine, for a fact. They call her the most popular nurse at the front, and I've heard fellows in plenty say that if ever they got knocked out by Hun bullets they'd want nothing better than to have her take care of them."

He did not find Jack anywhere around when he got back, nor had those he asked seen anything of him since early morning. Of course Tom knew what it was that engaged the attention of his comrade, and he only hoped Jack might not meet with any bad luck in his endeavor to learn something of the movements of his cousin, Randolph Carringford.

Then came the afternoon. From indications Tom fancied that would be their last night in the old dugout. The Huns were still falling back, and word had been going around that by another day the Yankees would undoubtedly occupy the village that lay just beyond the hills where the bursting shrapnel had ascended on the occasion of the passage of the air squadron.

It was about four o'clock when Tom sighted his chum. Jack's face was gloomy, and he lacked his customary sprightliness of walk.

As he came up he tried to smile, but it was a rank failure.

"Well," he said disconsolately, "the very worst has happened, Tom. I've managed to get word after trying for hours, and have learned that my cousin sailed yesterday from Havre. He's beat me to it, and I've lost out!"