"We have news," was the cautious answer, as the Nihilist slipped in, and closed the door behind him. "News of my brother?" "Of your brother! He is in a sulphur mine in the Altai Mountains, near the city of Abakansk." "Where's that?" asked Tom for he had forgotten most of his Russian geography. "The Altai Mountains are a range about the middle of Siberia," explained Mr. Petrofsky. "They begin at the Kirghiz Steppes, and run west. It is a wild and desolate place. I hope we can find poor Peter alive." "And this city of Abakansk?" went on the young inventor. "It is many miles from here, but I can give you a good map," said the Nihilist. "Some of our friends are there," he added with a half-growl. "I wish we could rescue all of them." "We'd like to," spoke Tom. "But I fear it is impossible. But now that we have a clew, come on! Let's start at once! It may be dangerous to stay here. On to Siberia!" CHAPTER XVIII IN A RUSSIAN PRISON The news they had waited for had come at last. It might be a false clew, but it was something to work on, and Tom was tired of inaction. Then, too, even after they had started, the prisoner might be moved and they would have to trace him again. "But that is the latest information we could get," said Mr. Androwsky. "It came through some of our Anarchist friends, and I believe is reliable. Can you soon make a thousand miles in your airship?" "Yes," answered Tom, "if I push her to the limit." "Then do so," advised the Nihilist, "for there is need of haste. In making inquiries our friends might incur suspicions and Peter Petrofsky may be exiled to some other place." "Oh, we'll get there," cried Tom. "Ned, see to the gas machine. Mr. Damon, you can help me in the pilot house." "Here is a map of the best route," said the Nihilist, as he handed one to Mr. Petrofsky. "It will take you there the shortest way. But how can you steer when high in the air?" "By compass," explained Tom. "We'll get there, never fear, and we're grateful for your clew." "I never can thank you enough!" exclaimed the exile, as he shook hands with Mr. Androwsky. The Nihilist left, after announcing that, in the event of the success of Tom and his friends, and the rescue of the exile from the sulphur mine, it would probably become known to them, as such news came through the Revolutionary channels, slowly but surely. "Here we go!" cried the young inventor gaily, as he turned the starting lever in the pilot house, and silently, in the darkness of the night, the Falcon shot upward. There was not a light on board, for, though small signal lamps had been kept burning when the craft was in the forest, to guide the Nihilists to her, now that she was up in the air, and in motion, it was feared that her presence would become known to the authorities of the town, so even these had been extinguished.