The blow had descended so suddenly that it was paralyzing. Tom and his friends did not know what to do, but they saw the wisdom of the course of leaving everything to Ivan Petrofsky. lie was a Russian, and he knew the Russian police ways--to his sorrow.

"I'm not afraid, said Tom, when they had been locked in a large prison room, evidently set apart for the use of political, rather than criminal, offenders. "We're United States citizens, and once our counsel hears of this--as he will--there'll be some merry doings in Oskwaski, or whatever they call this place. But I am worried about what they may do to the Falcon."

"Have no fears on that score," said the Russian exile. "They know the value of a good airship, and they won't destroy her."

"What will they do then?" asked Tom.

"Keep her for their own use, perhaps."

"Never!" cried Tom. "I'll destroy her first!"

"If you get the chance!" interposed the exile.

"But we're American citizens!" cried Tom, "and--"

"You forget that I am not," interrupted Mr. Petrofsky. "I can't claim the protection of your flag, and that is why I wish to remain unknown. We must act quietly. The more trouble we make, the more important they will know us to be. If we hope to accomplish anything we must act cautiously."

"But my airship!" cried Tom.

"They won't do anything to that right away," declared the Russian in a whisper for he knew sometimes the police listened to the talk of prisoners. "I think, from what I overheard when they arrested us, that we either trespassed on the grounds of some one in authority, who had us taken in out of spite, or they fear we may be English or French spies, seeking to find out Russian secrets."

They were served with food in their prison, but to all inquiries made by Ivan Petrofsky, evasive answers were returned. He spoke in poor, broken Russian, so that he would not be taken for a native of that country. Had he been, he would have at once been in great danger of being accused as an escaped exile.

Finally a man who, the exile whispered to his Companions, was the local governor, came to their prison. He eagerly asked questions as to their mission, and Mr. Petrofsky answered them diplomatically.

"I don't think he'll make much out of what I told him," said the exile when the governor had gone. "I let him think we were scientists, or pleasure seekers, airshipping for our amusement. He tried to tangle me up politically, but I knew enough to keep out of such traps."

"What's going to become of us?" asked Ned.

"We will be detained a few days--until they find out more about us. Their spies are busy, I have no doubt, and they are telegraphing all over Europe about us."

"What about my airship?" asked Tom.

"I spoke of that," answered the exile. "I said you were a well-known inventor of the United States, and that if any harm came to the craft the Russian Government would not only be held responsible, but that the governor himself would be liable, and I said that it cost much money. That touched him, for, in spite of their power, these Russians are miserably paid. He didn't want to have to make good, and if it developed that he had made a mistake in arresting us, his superiors would disclaim all responsibility, and let him shoulder the blame. Oh, all is not lost yet, though I don't like the looks of things."

Indeed it began to seem rather black for our friends, for, that night they were taken from the fairly comfortable, large, prison room, and confined in small stone cells down in a basement. They were separated, but as the cells adjoined on a corridor they could talk to each other. With some coarse food, and a little water, Tom and his friends were left alone.

"Say I don't like this!" cried our hero, after a pause.

"Me either," chimed in Ned.

"Bless my burglar alarm!" exclaimed Mr. Damon. "It's an awful disgrace! If my wife ever heard of me being in jail--"

"She may never hear of it!" interposed Tom.

"Bless my heart!" cried the odd man. "Don't say such things."

They discussed their plight at length, but nothing could be done, and they settled themselves to uneasy slumber. For two days they were thus imprisoned, and all of Mr. Petrofsky's demands that they be given a fair trial, and allowed to know the nature of the charge against them, went for naught. No one came to see them but a villainous looking guard, who brought them their poor meals. The governor ignored them, and Mr. Petrofsky did not know what to think.

"Well, I'm getting sick of this!" exclaimed Tom--I wish I knew where my airship was."

"I fancy it's in the same place," replied the exile. "From the way the governor acted I think he'd be afraid to have it moved. It might be damaged. If I could only get word to some of my Revolutionary friends it might do some good, but I guess I can't. We'll just have to wait."

Another day passed, and nothing happened. But that night, when the guard came to bring their suppers, something did occur.

"Hello! we've got a new one!" exclaimed Tom, as he noted the man. "Not so bad looking, either."

The man peered into his cell, and said something in Russian.

"Nothing doing," remarked the young inventor with a short laugh. "Nixy on that jabbering."

But, no sooner had the man's words penetrated to the cell of Ivan Petrofsky, that the exile called out something. The guard started, hastened to that cell door, and for a few seconds there was an excited dialogue in Russian.

"Boys! Mr. Damon! We're saved!" suddenly cried out Mr. Petrofsky.

"Bless my door knob! You don't say so!" gasped the odd man. "How? Has the Czar sent orders to release us."

"No, but somehow my Revolutionary friends have heard about my arrest, and they have arranged for our release--secretly of course. This guard is affiliated with the Nihilist group that got on the trail of my brother. He bribed the other guard to let him take his place for to-night, and now

"Yes! What is it?" cried Tom.

"He's going to open the cell doors and let us out!"

"But how can we get past the other guards, upstairs?" asked Ned.

"We're not going that way," explained Mr. Petrofsky. "There is a secret exit from this corridor, through a tunnel that connects with a large salt mine. Once we are in there we can make our way out. We'll soon be free."

"Ask him if he's heard anything of my airship?" asked Tom. Mr. Petrofsky put the question rapidly in Russian and then translated the answer.

"It's in the same place."

"Hurray!" cried Tom.

Working rapidly, the Nihilist guard soon had the cell doors open, for he had the keys, and our friends stepped out into the corridor.

"This way," called Ivan Petrofsky, as he followed their liberator, who spoke in whispers. "He says he will lead us to the salt mine, tell us how to get out and then he must make his own escape."

"Then he isn't coming with us?" asked Ned.

"No, it would not he safe. But he will tell us how to get out. It seems that years ago some prisoners escaped this way, and the authorities closed up the tunnel. But a cavein of the salt mine opened a way into it again."

They followed their queer guide, who led them down the corridor. He paused at the end, and then, diving in behind a pile of rubbish, he pulled away some boards. A black opening, barely large enough for a man to walk in upright, was disclosed.

"In there?" cried Tom.

"In there," answered Mr. Petrofsky. He and the guard murmured their good-byes, and then, with a lighted candle the faithful Nihilist had provided, and with several others in reserve, our friends stepped into the blackness. They could hear the board being pulled back into place behind them.

"Forward!" cried the exile, and forward they went.

It was not a pleasant journey, being through an uneven tunnel in the darkness. Half a mile later they emerged into a large salt mine, that seemed to be directly beneath the town. Work in this part had been abandoned long ago, all the salt there was left being in the shape of large pillars, that supported the roof. It sparkled dully in the candle light.

"Now let me see if I remember the turnings," murmured Mr. Petrofsky. "He said to keep on for half an hour, and we would come out in a little woods not far from where our airship was anchored."

Twisting and turning, here and there in the semi-darkness, stumbling, and sometimes falling over the uneven floor, the little party went on.

"Did you say half an hour?" asked Tom, after a while.

"Yes," replied the Russian.

"We've been longer than that," announced the young inventor, after a look at his watch. "It's over an hour."

"Bless my timetable!" cried Mr. Damon.

"Are you sure?" asked Mr. Petrofsky.

"Yes," answered Tom in a low voice.

The Russian looked about him, flashing the candle on several turnings and tunnels. Suddenly Ned uttered a cry.

"Why, we passed this place a little while before!" he said. "I remember this pillar that looks like two men wrestling!"

It was true. They all remembered it when they saw it again.

"Back in the same place!" mused the Russian. "Then we have doubled on our tracks. I'm afraid we're lost!"

"Lost in a Russian salt mine!" gasped Tom, and his words sounded ominous in that gloomy place.