Tom turned away from the window, to find his companions regarding him anxiously.

"A storm," repeated Ned. "What sort?"

"It might turn into any sort," replied Tom. "All I can see now is a lot of black clouds, and the wind must be blowing pretty hard, for there's quite a sea on."

"Bless my galvanometer!" cried Mr. Damon. "Then we are out over the ocean again, Tom?"

"Yes, there's no doubt of it."

"What part?" asked the assistant pilot.

"That's more than I can tell," Tom answered.

"Suppose I take a look?" suggested Captain Warner. "I've done quite a bit of sailing in my time."

But, when he had taken a look through the window at which Tom had been standing, the naval officer descended, shaking his head.

"There isn't a landmark in sight," he announced. "We might be over the middle of the Atlantic, for all I could tell."

"Hardly as far as that," spoke Tom. "They haven't been pushing the Mars at that speed. But we may be across to the other side before we realize it."

"How's that?" asked Ned.

"Well, the ship is in the possession of these foreign spies," went on Tom. "All their interests are in Europe, though it would be hard to say what nationality is in command here. I think there are even some Englishmen among those who attacked us, as well as French, Germans, Italians and Russians."

"Yes, it seems to be a combination of European nations against us," admitted Captain Warner. "Probably, after they have made good their seizure of Tom's aerial warship, they will portion her out among themselves, or use her as a model from which to make others."

"Do you think that is their object?" asked Mr. Damon.

"Undoubtedly," was the captain's answer. "It has been the object of these foreign spies, all along, not only to prevent the United States from enjoying the benefits of these progressive inventions, but to use them for themselves. They would stop at nothing to gain their ends. It seems we did not sufficiently appreciate their power and daring."

"Well, they've got us, at any rate," observed Tom, "and they may take us and the ship to some far-off foreign country."

"If they don't heave us overboard half-way there," commented Ned, in rather gloomy tones

"Well, of course, there's that possibility," admitted Tom. "They are desperate characters."

"Well, we must do something," declared Lieutenant Marbury. "Come, it's daylight now, and we can see to work better. Let's see if we can't find a way to get out of this prison. Say, but this sure is a storm!" he cried, as the airship rolled and pitched violently.

"They are handling her well, though," observed Tom, as the craft came quickly to an even keel. "Either they have a number of expert birdmen on board, or they can easily adapt themselves to a new aircraft. She is sailing splendidly."

"Well, let's eat something, and set to work," proposed Ned.

They brought out the food which had been given to them the night before, but before they could eat this, there came a knock on the door, and more food and fresh water was handed in, under the same precautions as before.

Tom and his companions indignantly demanded to be released, but their protests were only laughed at, and while the guards stood with ready weapons the door was again shut and locked.

But the prisoners were not the kind to sit idly down in the face of this. Under Tom's direction they set about looking through their place of captivity for something by which they could release themselves. At first they found nothing, and Ned even suggested trying to cut a way through the wooden walls with a fingernail file, which he found in one of his pockets, when Tom, who had gone to the far end of the storeroom, uttered a cry.

"What is it--a way out?" asked Lieutenant Marbury anxiously.

"No, but means to that end," Tom replied. "Look, a file and a saw, left here by some of my workmen, perhaps," and he brought out the tools. He had found them behind a barrel in the far end of the compartment.

"Hurray!" cried Ned. "That's the ticket! Now we'll soon show these fellows what's what!"

"Go easy!" cautioned Tom. "We must work carefully. It won't do to slam around and try to break down the door with these. I think we had better select a place on the side wall, break through that, and make an opening where we can come out unnoticed. Then, when we are ready, we can take them by surprise. We'll have to do something like that, for they outnumber us, you know."

"That is so," agreed Captain Warner. "We must use strategy."

"Well, where would be a good place to begin to burrow out?" asked Ned.

"Here," said Tom, indicating a place far back in the room. "We can work there in turns, sawing a hole through the wall. It will bring us out in the passage between the aft and amidship cabins, and we can go either way."

"Then let's begin!" cried Ned enthusiastically, and they set to work.

While the aerial warship pitched and tossed in the storm, over some part of the Atlantic, Tom and his friends took turns in working their way to freedom. With the sharp end of the file a small hole was made, the work being done as slowly as a rat gnaws, so as to make no noise that would be heard by their captors. In time the hole was large enough to admit the end of the saw.

But this took many hours, and it was not until the second day of their captivity that they had the hole nearly large enough for the passage of one person at a time. They had not been discovered, they thought.

Meanwhile they had been given food and water at intervals, but to all demands that they be released, or at least told why they were held prisoners, a deaf ear was turned.

They could only guess at the fate of Koku. Probably the giant was kept bound, for once he got the chance to use his enormous strength it might go hard with the foreigners.

The Mars continued to fly through the air. Sometimes, as Tom and his friends could tell by the motion, she was almost stationary in the upper regions, and again she seemed to be flying at top speed. Occasionally there came the sound of firing.

"They're trying my guns," observed Tom grimly.

"Do you suppose they are being attacked?" asked Ned, hopefully.

"Hardly," replied Captain Warner. "The United States possesses no craft able to cope with this one in aerial warfare, and they are hardly engaging in part of the European war yet. I think they are just trying Tom's new guns."

Later our friends learned that such was the case.

The storm had either passed, or the Mars had run out of the path of it, for, after the first few hours of pitching and tossing, the atmosphere seemed reduced to a state of calm.

All the while they were secretly working to gain their freedom so they might attack and overpower their enemies, they took occasional observations from the small window. But they could learn nothing of their whereabouts. They could only view the heaving ocean, far below them, or see a mass of cloud-mist, which hid the earth, if so be that the Mars was sailing over land.

"But how much longer can they keep it up?" asked Ned.

"Well, we have fuel and supplies aboard for nearly two weeks," Tom answered.

"And by the end of that time we may all be dead," spoke the young bank clerk despondently.

"No, we'll be out of here before then!" declared Lieutenant Marbury.

Indeed the hole was now almost large enough to enable them to crawl out one at a time. They could not, of course, see how it looked from the outside, but Tom had selected a place for its cutting so that the sawdust and the mark of the panel that was being removed, would not ordinarily be noticeable.

Their set night as the time for making the attempt--late at night, when it was hoped that most of their captors would be asleep.

Finally the last cut was made, and a piece of wood hung over the opening only by a shred, all ready to knock out.

"We'll do it at midnight," announced Tom.

Anxious, indeed, were those last hours of waiting. The time had almost arrived for the attempt, when Tom, who had been nervously pacing to and fro, remarked:

"We must be running into another storm. Feel how she heaves and rolls!"

Indeed the Mars was most unsteady.

"It sure is a storm!" cried Ned, "and a heavy one, too," for there came a burst of thunder, that seemed like a report of Tom's giant cannon.

In another instant they were in the midst of a violent thunderstorm, the airship pitching and tossing in a manner to almost throw them from their feet.

As Tom reached up to switch on the electric light again, there came a flash of lightning that well nigh blinded them. And so close after it as to seem simultaneous, there came such a crash of thunder as to stun them all. There was a tingling, as of a thousand pins and needles in the body of each of the captives, and a strong smell of sulphur. Then, as the echoes of the clap died away, Tom yelled:

"She's been struck! The airship has been struck!"