Dick Martin became frantic when he saw what was about to happen. He fairly tore at the various levers and controls, and even increased the speed of the motor, but this last only had the effect of sending the machine at a faster rate toward the big expanse of glass, which was the greenhouse roof.

“Shut it off! Shut off the motor!” cried Tom, but his words could not be heard, so he punched Martin in the back, and when that frightened lad looked around his teacher made him understand by signs, what was wanted.

With the motor off there was a chance to speak, and Torn cried:

“Head her up! Try to make her rise and we may clear. I can't do a thing with the levers back here!”

Martin tried, but his efforts had little effect. For one instant the machine rose as though to clear the fragile glass. Then it dived down again, straight for the greenhouse roof.

“Guess it's all up with this machine!” thought Tom quickly. He was not afraid of being killed. The distance to fall was not enough for that, and though he and his fellow aviator might be cut by broken glass, still the body of the aeroplane would protect them pretty well from even this contingency. But there was sure to be considerable damage to the property of a French civilian, and the machine, which was one of the best, was pretty certain to be badly broken.

And then there came a terrific crash. The aeroplane settled down by the stern, and rose by the bow, so to speak. Then the process was reversed, and Tom felt himself being catapulted out of his seat. Only his safety strap held him in place. The same thing happened to Dick Martin.

Then there was an ominous calm, and the aeroplane slowly settled down to an even keel, held up on the glass-stripped frames of the greenhouse, one of the very few in that vicinity, which was considerably in the rear of the battle line.

Slowly Tom unbuckled his safety strap and climbed out, making his way to the ground by means of stepping on an elevated bed of flowers inside the now almost roofless house.

Martin followed him, and as they stood looking at the wreckage they had made, or, rather, that had been made through no direct fault of their own, the proprietor of the place came out, wearing a long dirt-smudged apron.

He raised his hands in horror at the sight that met his gaze, and then broke into such a torrent of French that Tom, with all the experience he had had of excitable Frenchmen, was unable to comprehend half of it.

The gist was, however, to the effect that a most monstrous and unlooked-for calamity had befallen, and the inhabitants of all the earth, outside of Germany and her allies, were called on to witness that never hid there been such a smash of good glass. In which Torn was rather inclined to agree.

“Well, you did something this time all right, Buddie,” Tom remarked to Dick Martin.

“Did I—did I do that?” he asked, as though he had been walking in his sleep, and was just now awake.

“Well, you and the old bus together,” said Tom. “And we got off lucky at that. Didn't I tell you to keep high, if you were going to fly over one of the towns?”

By this time quite a crowd had gathered, and Tom was trying to pacify the excitable greenhouse owner by promising full reparation in the shape of money damages.

How to get the machine down off the roof, where it rested in a mass of broken glass and frames, was a problem. Tom tried to organize a wrecking party, but the French populace which gathered, much as it admired the Americans, was afraid of being cut with the broken glass, or else they imagined that the machine might suddenly soar aloft, taking some of them with it.

In the end Tom had to leave the plane where it was and hire a motor to take him and Martin back to the aerodrome. They were only slightly cut by flying glass, nothing to speak of considering the danger in which they had been.

The result of the disobedience of orders was that the army officials had rather a large bill for damages to settle with the French greenhouse proprietor, and Tom and Dick Martin were deprived of their leave privileges for a week for disobeying the order to keep at a certain height in flying over a town or city.

Had they done that, when the controls jammed, they would have been able to glide down into a vacant field, it was demonstrated. The machine was badly damaged, though it was not beyond repair.

“And that's the last time I'm ever going to be soft with a Hun, you can make up your mind to that,” declared Tom to Jack. “If I'd sat on him hard when I saw he was getting too low over the village, it wouldn't have happened. But I didn't want him to think I knew it all, and I thought I'd take a chance and let him pull his own chestnuts out of the fire. But never again!”

“'Tisn't safe,” agreed Jack. He was rapidly improving, so much so that he was able to fly the next week, and he and Tom went up together, and did some valuable scouting work for the American army.

At times they found opportunity to take short trips to Paris, where they saw Nellie and Bessie, and were entertained by Mrs. Gleason. Nellie was eager for some word from her brother, but none came. Whether the packages dropped by Tom and Jack reached the prisoner was known only to the Germans, and they did not tell.

But the daring plan undertaken by the two air service boys was soon known a long way up and down the Allied battle line, and more than one aviator tried to duplicate it, so that friends or comrades who were held by the Huns might receive some comforts, and know they were not forgotten. Some of the Allied birdmen paid the penalty of death for their daring, but others reported that they had dropped packages within the prison camps, though whether those for whom they were intended received them or not, was not certain.

“But we aren't going to let it stop there, are we?” asked Tom of Jack one day, when they were discussing the feat which had been so successful.

“Let it stop where? What do you mean?”

“I mean are we going to do something to get Harry away from the Boche nest?”

“I'm with you in anything like that!” exclaimed Jack. “But what can we do? How are we going to rescue him?”

“That's what we've got to think out,” declared Tom. “Something has to be done.”

But there was no immediate chance to proceed to that desired end because of something vital that happened just about then. This was nothing more nor less than secret news that filtered into the Allied lines, to the effect that a big Zeppelin raid over Paris was planned.

It was not the first of these raids, nor, in all likelihood, would it be the last. But this one was novel in that it was said the great German airships would sail toward the capital over the American lines, or, rather, the lines where the Americans were brigaded with the French and English. Doubtless it was to “teach the Americans a lesson,” as the German High Command might have put it.

At any rate all leaves of absence for the airmen were canceled, and they were ordered to hold themselves in readiness to repel the “Zeps,” as they were called, preventing them from getting across the lines to Paris.

“And we'll bring down one or two for samples, if we can!” boasted Jack.

“What makes it so sure that they are coming?” asked Tom.

It developed there was nothing sure about it. But the information had come from the Allied air secret service, and doubtless had its inception when some French or British airman saw scenes of activity near one of the Zeppelin headquarters in the German-occupied territory. There were certain fairly positive signs.

And, surely enough, a few nights later, the agreed-upon alarm was sounded.

“The Zeps are coming!”

Tom and Jack, with others who were detailed to repel the raid, rushed from their cats, hastily donned their fur garments, and ran to their aeroplanes, which were a “tuned up” and waiting.

“There they are!” cried Torn, as he got into his single-seated plane, an example followed on his part by Jack. “Look!”

Jack gazed aloft. There was a riot of fire from the anti-aircraft guns of the French and British, but they were firing in vain, for the Zeppelins flew high, knowing the danger from the ground batteries.

Sharp, stabbing shafts of light from the powerful electric lanterns shot aloft, and now and then one of them would rest for an instant on a great silvery cigar-shape—the gas bag of the big German airships that were beating their way toward Paris, there to deal death and destruction.

“Come on!” cried Tom, as his mechanician started the motor. “I'm going to get a Zep!”

“I'm with you!” yelled Jack, and they soared aloft side by side.