"Greetings, gentlemen--and the little lady," boomed their host, with heavy affability. "I see that my men were in time. These swine of Antillians are a tricky lot. I must apologize for them--my subjects." The last word was pronounced with scathing contempt. "We return greetings!" said Professor Stevens. "To whom, might I ask, do we owe our lives, and the honor of this interview?" Larry smiled. The old graybeard was up to his form, all right! "You are addressing Herr Rolf von Ullrich," the flattered German replied, adding genially: "commander of one of His Imperial Majesty's super-submarines during the late war and at present Emperor of Antillia." To which the professor replied with dignity that he was greatly honored to make the acquaintance of so exalted a personage, and proceeded in turn to introduce himself and party. But Von Ullrich checked him with a smile. "The distinguished Professor Stevens and his charming daughter need no introduction, as they are already familiar to me through the American press and radio," he said. "While as for Mr. Hunter, your Captain Petersen has already made me acquainted with his name." At the mention of the commander of the _Nereid_, all three of them gave a start. "Then--then my captain and crew are safe?" asked the professor, eagerly. "Quite," Von Ullrich assured him. "You will be taken to them presently. But first there are one or two little things you would like explained--yes? Then I shall put to you a proposal, which if acceptable will guarantee your safe departure from my adopted country." Whereupon the German traced briefly the events leading up to the present. * * * * * During the last months of the war, he had been placed in command of a special U-boat known as the "mystery ship"--designed to resist depth-charges and embodying many other innovations, most of them growing out of his own experience with earlier submarines. One day, while cruising off the West Indies, in wait for some luckless sugar boat, he had been surprised by a destroyer and forced to submerge so suddenly that his diving gear had jammed and they had gone to the bottom. But the craft had managed to withstand the pressure and they had been able to repair the damage, limping home with a bad leak but otherwise none the worse for the experience. The leak repaired and the hull further strengthened, he had set out again. But when in mid-Atlantic the Armistice had come, and rather than return to a defeated country, subject possibly to Allied revenge, he had persuaded his crew to remain out and let their craft be reported missing. What followed then, though Von Ullrich masked it in polite words, was a story of piracy, until they found by degrees that there was more gold on the bottom of the ocean than the top; and from this to the discovery of the sunken empire where he now held reign was but a step.