"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 be 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 cave-in 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.