"Have we--have we time to get a drink?" gasped Ned, when the aeroplane, now on a level keel, had been shooting forward about three minutes. Already it was beyond the reach of the rifles.

"Yes, but take only a little," cautioned Tom. "Oh! it doesn't seem possible that we are free!"

He switched on a few interior lights, and by their glow the faint and starving platinum-seekers found water and food. Their craft had, apparently, not been touched in their absence, and the machinery ran well.

Cautiously they ate and drank, feeling their strength come back to them, and then they removed the traces of their terrible imprisonment, and set about in ease and comfort, talking of what they had suffered.

Onward sped the aeroplane, onward through the night, and then Tom, having set the automatic steering gear, all fell into heavy slumbers that lasted until far into the next day.

When the young inventor awoke he looked below and could see nothing--nothing but a sea of mist.

"What's this?" he cried. "Are we above the clouds, or in a fog over some inland sea?"

He was quite worried, until Ivan Petrofsky informed him that they were in the midst of a dense fog, which was common over that part of Siberia,

"But where are we?" asked Ned.

"About over the province of Irtutsk," was the answer. "We are heading north," he went on, as he looked at the compass, "and I think about right to land somewhere near where my brother is confined in the sulphur mine."

"That's so; we've got to drop," said Tom. "I must get the gas pipe repaired. I wish we could see over what soft of a place we were so as to know whether it would be safe to land. I wish the mist would clear away."

It did, about noon, and they noted that they were over a desolate stretch of country, in which it would be safe to make a landing.

Bringing the aeroplane down on as smooth a spot as he could pick out, Tom and Ned were soon at work clearing out the clogged pipe of the gas generator. They had to take it out in the open air, as the fumes were unpleasant, and it was while working over it that they saw a shadow thrown on the ground in front of them. Startled they looked up, to see a burly Russian staring at them.

The sudden appearance of a man in that lonely spot, his calm regard of the lads, his stealthy approach, which had made it possible for him to be almost upon them before they were aware of his presence, all this made them suspicious of danger. Tom gave a quick glance about, however, and saw no others--no Cossack soldiers, and as he looked a second time at the man he noted that he was poorly dressed, that his shoes were ragged, his whole appearance denoting that he had traveled far, and was weary and ill.

"What do you make of this, Ned?" asked Tom, in a low voice.

"I don't know what to make of it. He can't be an officer, in that rig, and he has no one with him. I guess we haven't anything to be afraid of. I'm going to ask him what he wants."

Which Tom did in his plainest English. At once the man broke into a stream of confused Russian, and he kept it up until Tom held up his hand for silence.

"I'm sorry, but I can't understand you," said the young inventor. "I'll call some one who can, though," and, raising his voice, he summoned Ivan Petrofsky who, with Mr. Damon, was inside the airship doing some small repairs.

"There's a Russian out here, Mr. Petrofsky," said Tom, "and what he wants I can't make out."

The exile was quickly on the scene and, after a first glance at the man, hurried up to him, grasped him by the hand and at once the two were talking such a torrent of hard-sounding words that Tom and Ned looked at each other helplessly, while Mr. Damon, who had come out, exclaimed:

"Bless my dictionary! they must know each other."

For several minutes the two Russians kept up their rapid- fire talk and then Mr. Petrofsky, evidently realizing that his friends must wonder at it, turned to them and said:

"This is a very strange thing. This man is an escaped convict, as I once was. I recognized him by certain signs as soon as I saw him, though I had never met him before. There are certain marks by which a Siberian exile can never be forgotten," he added significantly. "He made his escape from the mines some time ago, and has suffered great hardships since. The revolutionists help him when they can, but he has to keep in concealment and travels from town to town as best he may. He has heard of our airship, I suppose from inquiries the revolutionists have been making in our behalf, and when he unexpectedly came upon us just now he was not frightened, as an ordinary peasant would have been. But he did not know I was aboard."

"And does he know you?" asked Tom. "Does he know you are trying to rescue your brother?"

"No, but I will tell him."

There was another exchange of the Russian language, and it seemed to have a surprising result. For, no sooner had Ivan Petrofsky mentioned his brother, than the other, whose name was Alexis Borious seemed greatly excited. Mr. Petrofsky was equally so at the reply his new acquaintance made, and fairly shouted to Tom, Ned and Mr. Damon.

"Friends, I have unexpected good news! It is well that we met this man or we would have gone many miles out of our way. My brother has been moved to another mine since the revolutionists located him for me. He is in a lonely district many miles from here. This man was in the same mine with him, until my brother was transferred, and then Mr. Borious escaped. We will have to change our plans."

"And where are we to head for now?" asked Tom.

"Near to the town of Haskaski, where my poor brother is working in a sulphur mine!"

"Then let's get a move on!" cried Tom with enthusiasm. "Do you think this man will come with us, Mr. Petrofsky, to help in the rescue, and show us the place?"

"He says he will," translated the exile, "though he is much afraid of our strange craft. Still he knows that to trust himself to it is better than being captured, and sent back to the mines to starve to death!"

"Good!" cried Tom. "And if he wants to, and all goes well, we'll take him out of Russia with us. Now get busy, Ned, and we'll have this machine in shape again soon.

While Ivan Petrofsky took his new friend inside, and explained to him about the workings of the Falcon, Tom and Ned labored over the gas machine with such good effect that by night it was capable of being used. Then they went aloft, and making a change in their route, as suggested by Mr. Borious, they headed for the desolate sulphur region.

For several days they sailed on, and gradually a plan of rescue was worked out. According to the information of the newcomer, the best way to save Mr. Petrofsky's brother was to make the attempt when the prisoners were marched back from the mines to the barracks where they were confined.

"It will be dark then," said Mr. Borious, "and if you can hover in your airship near at hand, and if Mr. Petrofsky can call out to his brother to run to him, we can take him up with us and get away before the guards know what we are doing."

"But aren't the prisoners chained?" asked Tom.

"No, they depend on guards to prevent escapes."

"Then we'll try that way," decided the young inventor.

On and on they sailed, the Falcon working admirably. Verst after verst was covered, and finally, one morning, Mr. Borious, who knew the country well, from having once been a prisoner there, said:

"We are now near the place. If we go any closer we may be observed. We had better remain hidden in some grove of trees so that at nightfall we can go forth to the rescue."

"But how can we find it after dark?" asked Ned.

"You can easily tell by the lights in the barracks," was the answer. "I can stand in the pilot house to direct you, for nearly all these exile prisons are alike. The prisoners will march in a long line from the mine. Then for the rescue."

It was tedious waiting that day, but it had to be done, and to Tom, who was anxious to effect the rescue, and proceed to the place of the winds to try his air glider, it seemed as if dusk would never come as they remained in concealment.

But night finally approached and then the great airship went silently aloft, ready to hover over the prison ground. Fortunately there was little wind; and she could be used as a balloon, thus avoiding the noise of the motor.

"The next thing I do, when I get home," remarked Tom, as they drifted along. "Will be to make a silent airship. I think they would be very useful."

With Mr. Borious in the pilot house, to point out the way, Tom steered through the fast-gathering darkness. The Russian had soon become used to the airship, and was not at all afraid.

"Can you go just where you want to, as a balloon?" asked the new guide.

"No, but almost," replied Tom. "At the last moment I've got to take a chance and start the motor to send us just where we want to go. That's why I think a silent airship would be a great thing. You could get up on the enemy before he knew it."

"There are the prison barracks," said the guide a little later, his talk being translated by Mr. Petrofsky. Below and a little ahead of them could been seen a cluster of lights.

"Yes, that looks like a line of prisoners," remarked Ned, who was peering through a pair of night glasses.

"Where?" asked Tom eagerly, and they were pointed out to him. He took an observation, and exclaimed:

"There they are, sure enough. Now if your brother is only among them, Mr. Petrofsky, we'll soon have him on board."

"Heaven grant that he may be there!" said the exile in a low voice.

A moment later, the Falcon, meanwhile having been allowed to drift as close as possible to the dimly-seen line of prisoners, Tom set in motion the great motor, the propeller blades heating the air fiercely.

At the sound there was a shout on the ground below, but before the excitement had time to spread, or before any of the guards could form a notion of what was about to take place, Tom had sent his craft to earth on a sharp slant, closer to the line of prisoners than he had dared to hope.

Mr. Petrofsky sprang out on deck, and in a loud voice called in Russian:

"Peter! Peter! If you are there, come here! Come quickly! It is I, your brother Ivan who speaks. I have come to save you--save you in the wonderful airship of Tom Swift! Come quickly and we will take you away! Peter Petrofsky!"

For a moment there was silence, and then the sound of some one running rapidly was borne to the ears of the waiting ones. It was followed, a moment later, by angry shouts from the guards.

"Quick! Quick, Peter!" cried the brother, "over this way!"

For an instant only the exile showed a single electric flash light, that his brother might see in which direction to run. The echo of the approaching footsteps came nearer, the shouts of the guards redoubled, and then came the sound of many men running in pursuit.

"Hurry, Peter, hurry!" cried Mr. Petrofsky, and, as he spoke in Russian the guards, of course, understood.

Suddenly a rifle shot rang out, but the weapon seemed to have been fired in the air. A moment later a dark figure clambered aboard the airship.

"Peter, is it you?" cried Ivan Petrofsky, hoarsely.

"Yes, brother! But get away quickly or the whole guard will be swarming about here!"

"Praise the dear Lord you are saved!"

"Is it all right?" cried Tom, who wanted to make sure they were saving the right man.

"Yes! Yes, Tom! Go quickly!" called Ivan Petrofsky, as he folded his brother in his arms. A moment later, with a roar, the Falcon shot away from the earth, while below sounded angry cries, confused shouts and many orders, for the guards and their officers had never known of such a daring rescue as this.