For three days more they lingered, and then, one night, when they were just getting ready to retire, there was a knock on the cabin door. Mr.

Petrofsky had been to the village that day, and had received no news.

He had only returned about an hour before.

"Some one's knocking," announced Ned, as if there could be any doubt of it.

"Bless my burglar alarm!" gasped Mr. Damon.

"I'll see who it is," volunteered Mr. Petrofsky, and Tom looked toward the rack of loaded rifles, for that day a man, seemingly a wood cutter had pa.s.sed close to the airship, and had hurried off as if he had seen a ghost.

The knock was repeated. It might be their friends, and it might be--

But Mr. Petrofsky solved the riddle by throwing back the portal, and there stood the Nihilist, Nicolas Androwsky.

"Is there anything the matter?" asked the exile quickly.

"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 compa.s.s," 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.

"After we get well away we can turn on the electrics," remarked Tom, "and if they see us at a distance they may take us for a meteor. But, so close as this, they'd get wise in a minute."

Mr. Damon, who had done all that Tom needed in the starting of the craft, went to the forward port rail, and idly looked down on the black forest they were leaving. He could just make out the clearing where they had rested for over a week, and he was startled to see lights bobbing in it.

"I say, Mr. Petrofsky!" he called. "Did we leave any of our lanterns behind us?"

"I don't believe so," answered the exile. "I'll ask Tom."

"Lanterns? No," answered the young inventor. "Before we started I took down the only one we had out. I'll take a look."

Setting the automatic steering apparatus, he joined Mr. Damon and the Russian. The lights were now dimly visible, moving about in the forest clearing.

"It's just as if they were looking for something," said Tom. "Can it be that any of your Nihilist friends, Mr. Petrofsky are--"

"Friends--no friends--enemies!" cried the Russian. "I understand now!

We got away just in time. Those are police agents who are looking for us! They must have received word about our being there. Androwsky and the others never carry lights when they go about. They know the country too well, and then, too, it leads to detection. No, those are police spies. A few minutes later, and we would have been discovered."

"As it is we're right over their heads, and they don't know it,"

chuckled Tom. The airship was moving silently along before a good breeze, the propellers not having been started, and Tom let her drift for several miles, as he did not want to give the police spies a clew by the noise of the motor.

The twinkling lights in the forest clearing disappeared from sight, and the seekers went on in the darkness.

"Well, we've got the hardest part of our work yet ahead of us,"

remarked Tom several hours later when, the lights having been set aglow, they were gathered in the main cabin. There was no danger of being seen now, for they were quite high.

"We've done pretty well, so far," commented Ned. "I think we will have easier work rescuing Mr. Petrofsky's brother than in locating the mine.

"I don't know about that," answered the Russian. "It is almost impossible to rescue a person from Siberia. Of course it is not going to be easy to locate the lost mine, but as for that we can keep on searching, that is if the air glider works, but there are so many forces to fight against in rescuing a prisoner."

They had a long journey ahead of them, and not an easy route to follow, but as the days pa.s.sed, and they came nearer and nearer to their goal, they became more and more eager.

They were pa.s.sing over a desolate country, for they avoided the vicinity of large towns and cities.

"I wonder when we'll strike Siberia?" mused Tom one afternoon, as they sat on the outer deck, enjoying the air.