"Four," replied Jack briefly, now beginning to smile to himself, for he saw the German did not know what had happened. "Which way did they go?" demanded the German. "Straight to the bottom," replied Jack, with a note of thankfulness in his voice. "What!" exclaimed the officer, starting to his feet. "To the bottom," Jack repeated. "Impossible!" cried the officer. "One British ship couldn't sink four German torpedo destroyers." "I didn't say there was only one," said Jack. "We some assistance." "You must have had," said the German officer heatedly. "How many? A dozen?" "There were two or three," said Jack briefly, He had no mind to tell the German officer the size of the British squadron. The German officer was silent for several minutes and then he said: "Why didn't you tell me this in the first place?" "You didn't ask me," replied Jack, with a tantalizing laugh. The German brought his right fist into the palm of his left hand with a resounding smack. "You English will pay dearly for every German ship stink," he exclaimed. "Maybe so," replied Jack, dryly, "but it won't be a German fleet that makes us pay." "Enough of this!" broke in the second German officer. "Lieutenant Stein, you forget yourself, sir. And as for you, sir," turning to Jack, "you show no better taste." "I beg your Pardon," said Jack. "I wouldn't have said anything if he hadn't egged me on." Lieutenant Stein was equally repentant. "I apologize," he said quietly to Jack. "I should not have spoken as I did." "Say no more about it," said Jack. "I was just as much to blame." Frank now broke into the conversation. "What vessel is this?" he asked, pointing to the low-lying bulk of the submarine, against which the small boat now scraped. "German submarine X-9," replied Lieutenant Stein, "where, until we put into port again, you will be our prisoners." The four now clambered to the top of the submarine. Lieutenant Stein led the way to the entrance through the combined bridge and conning tower, and all went below. At the foot of the short flight of steps stood a man in captain's uniform. "The sole survivors of a British cruiser, sir," said Lieutenant Stein to the captain, indicating the two lads. "I have not learned their names nor rank." The two lads hastened to introduce themselves. "I am Captain von Cromp, commander of this vessel," said the captain gruffly. "You are my prisoners until I put into port and can turn you over to the proper authorities." Jack and Frank bowed in recognition of their fate. The captain turned to Lieutenant Stein. "You will see that the prisoners are well cared for," he said. "They are in your custody." The lads glanced curiously about as they were led along toward the lieutenant's cabin. It was the first time either had been inside a submarine vessel, and both felt a trifle squeamish. The boat was upon the surface of the sea now, however, and a dim light penetrated below.