Frank tinkered with the motor and took a firm grip on the wheel. But the hydroplane did not move. "Something wrong," said Frank, quietly. "What?" demanded Jack. "Something wrong with the motor. It won't work." Frank had bent over and was examining it carefully. Came a shot from the German torpedo boat. "If we don't get out of here pretty quick," said Jack, quietly, "we won't get out at all." Frank made no reply, but continued to tinker with the engine. A second shot from the German torpedo boat. It skimmed the water ahead of the hydroplane. Jack gazed toward the vessel. As he did so a small boat put off from the German and headed toward them. "They're coming after us, Frank," said Jack, "a whole boatload of 'em. How long will it take you to fix that thing?" Frank uttered an exclamation of satisfaction. "I've found it," he cried. "Five minutes," he answered Jack's question. "Five minutes is liable to be too late," returned Jack, measuring the distance to the rapidly approaching German boat with his eye. "However, hurry as much as you can." Frank did not take his eye from his engine. "How far away?" he asked as he worked. "Three quarters of a mile," replied Jack, calmly. "Lots of time for us, then," said Frank, still working as swiftly as possible. "Maybe," replied his chum. "Don't forget they carry pretty fair rifles with them." "If we can get started before they shoot, I'll guarantee they don't get us," returned Frank. "Well, they'll get us if you keep talking and don't get a move on there," said Jack. "They're coming like the wind." "That's just the way I'm working. She's almost fixed row. Can you hold them off?" "What, with a single revolver against a score of rifles? Not much. They're right on us now. How's that engine?" "Fixed!" cried Frank at that moment, straightening up. "All right. Let her go then," said Jack, calmly. "They don't know yet that we're going to run. They have made no preparations to fire. Evidently they think we shall wait for them." Even while Jack was speaking, the hydroplane began to move slowly over the surface of the water. Very slowly it went at first, then faster and faster. "Halt!" came a cry from the German boat. Jack picked up his cap and waved it at the Germans. "Some other time," he called back. "We're terrible busy today. Goodbye." The German officer gave a sharp command. Several sailors sprang to their feet and blazed away at the hydroplane with their rifles. Bullets flew by on all sides, but none struck home. Again Jack waved his cap. "Very bad shooting," he remarked. "Looks like some of my--Hello! That wasn't so bad." For the lad's cap, which he had been waving in derision at the pursuing foe, was suddenly carried from his hand by a German bullet. "By Jove!" said Jack, quietly, "I wouldn't have lost that cap----" He gazed at it as it floated in the water. And at that instant Frank sent the hydroplane soaring into the air with a lurch. Jack glanced down into the water.