Mr. Petrofsky, turning his telescope on the craft behind them.
"I can let them get almost up to us, and get away," replied Tom.
The Russian did not answer. He was gazing earnestly at the approaching aeroplane. A moment later he took the glass down from his eye.
"It's our spy again," he said. "There are two others with him. That is one of the aeroplanes owned by the secret police. They are stationed all over Europe, ready for instant service, and they're on our trail."
The pursuing craft was so near that the occupants could easily be made out with the naked eye, but it needed the glass to distinguish their features, and Mr. Petrofsky had done this.
"Shall I speed up?" cried Tom.
"Yes, get away as fast as you can!" shouted the Russian. "No telling what they may do," and then, with a hum and a roar the motor of the Falcon increased its speed, and the big airship shot ahead.
