The next instant a big piece of driftwood crashed through the casement, just as the two men were hurrying to the front door to answer Tom's summons. "Mr. Petrofsky! This way!" yelled Mr. Damon, sticking his head in through the broken sash. "Come out! We've come to save you! Bless my putty blower, but this is great! Come on!" For a moment the exile stared at the head thrust through the broken window, and he listened to Tom's emphatic knocks and demands. Then with a cry of delight the Russian sprang for the open casement, while the guard that had remained near him made a leap to catch him, crying out: "Betrayed! Betrayed! It's the Nihilists! Look out, comrades!" CHAPTER VII THE AIR GLIDER Mr. Damon continued to hammer away at the window sash with the piece of driftwood. There were splinters of the frame and jagged pieces of glass sticking out, making it dangerous for the exile to slip through. "Come on! Come on!" the eccentric man continued to call. "Bless my safety valve! We'll save you! Come on!" Mr. Petrofsky was leaping across the room, just ahead of the one guard. The other two were at the open door now, through which Tom could be seen. Then the spies, realizing in an instant that they had been deceived, made a dash after their comrade, who had his hand on the tails of the exile's coat. "Break away! Break loose!" cried Mr. Damon, who, by this time had cleared the window so a person could get through. "Don't let them hold you!" "I don't intend to!" retorted Mr. Petrofsky, and he swerved suddenly, tearing his coat, from the grasp of the guard. In another instant the exile was at the casement, and was being helped through by Mr. Damon, and there was need of it, for the three guards were there now, doing their best to keep their prisoner. "Pull away! Pull away!" cried Mr. Damon. "We'll help you!" shouted Tom, who, now that his trick had worked, had sped around to the other side of the hut. "Don't be afraid, we're with you!" exclaimed the detective, who was with the young inventor. "Grab him! Keep him! Hold him!" fairly screamed the rearmost of the three guards. "It is a plot of the Nihilists to rescue him. Shoot him, comrades. He must not get away!" "Don't you try any of your shooting games, or I'll take a hand in it!" shouted the detective, and, at the same moment he drew his revolver and fired harmlessly in the air. "A bomb! A bomb!", yelled the guards in terror. "Not yet, but there may be!" murmured Tom. The firing of the shot produced a good effect, for the three men who were trying to detain Ivan Petrofsky at once fell back from the window and gave him just the chance needed. He scrambled through, with the aid of Mr. Damon, and before the guards could again spring at him, which they did when the echoes of the shot had died away. They had realized, too late, that it was not a bomb, and that there was no immediate danger for them. "Come on!" cried Tom. "Make for the airship! We've got to get the start of them!"