At the same moment the submarine was made as bright as day by the powerful rays of a searchlight which fell upon it; but this glare was a boon to Frank, for it gave him a chance to determine his opponent's position, and he was not slow to take advantage of it. With right and left he struck out swiftly time after time, and the Turk, badly battered, at last tumbled from the bridge and into the sea with a howl of pain. At the same instant other figures began to clamber over the side of the submarine, where they had been attracted by the sounds of confusion. Frank acted quickly. Jumping to his feet, he dashed below, closing the door to the bridge and conning tower after him. "Submerge!" he cried as the doors came together with a clang. In vain did the figures upon the top of the D-16 seek to retain a foothold. Their foundation slipped gradually away from them, until they were all left floundering in the sea. Then the D-16 turned in the direction of the allied fleet. CHAPTER XXVII. A DESPERATE UNDERTAKING. The D-16 made the return journey very slowly, for the master hand of Lord Hastings was lacking and Frank, being no navigator and his knowledge of the lay of the land very poor, was forced to proceed cautiously. In Lord Hastings' cabin, Jack was still busy dressing his commander's wound. He found, after an examination, that it was not as serious as he had at first feared. The long bladed knife had caught Lord Hastings on the left side, halfway between the waist and the shoulder, and, turning up, had opened a deep gash clear to the shoulder. Lord Hastings was very weak, for the wound had bled profusely, but he was in no danger. Jack performed a creditable operation upon the wound, and after he had bandaged it carefully, Lord Hastings lay back and went quietly to sleep. Then Jack took command of the vessel. It was early morning when Jack gave the signal to rise, for he wanted to be sure that he had passed all danger points before coming to the surface. When they did bob up from beneath the water, he found that he had gone too far by more than a mile. However, no harm was done, and the D-16 was quickly brought about and soon lay under the lee of the _Queen Elizabeth_. Here she lay till midday when Jack went aboard to report. The commander was very anxious when he learned that Lord Hastings was wounded, but he accepted Jack's report instead and announced that he would visit Lord Hastings some time during the day. "Well," said Frank to his commander as he sat at his side, "I guess this settles our Constantinople trip." "Why so?" asked Lord Hastings. Frank was surprised. "Why we can't go with you in this condition," he replied. Lord Hastings smiled faintly. "A little thing like this is not going to stop me," he said. "True, I can do no fighting, but I can still navigate the boat." "But it is impossible," said Frank.