There was something rather disagreeably commanding in the German's invitation, but Jack merely smiled quietly as he followed in the stranger's wake. Up the stairs they went. The Professor unlocked a door, admitting himself and his guest to the outer of a suite of two rooms. Once they were inside Radberg locked the door behind them. "Come to the other room, Herr Benson," directed the Professor. The door of this inner room the German also locked, remarking: "Now, if the man, Holt, chooses to follow and listen, he can hear nothing." "All this sounds mighty mysterious," laughed Jack Benson, good-humoredly. However, the submarine boy went and stood by a chair near the window and then waited until he saw that the stranger was about to seat himself. "Now," asked Jack, stretching his legs, "what's the business about? I haven't a whole lot of time to-day." "Listen, and you shall hear, as soon as I am ready," came, stiffly, from the stranger. "You are a boy, and I am Herr Professor--" "Oh, you told me all about being a hair professor before," smiled Jack. "Now, see here. Whether you're really a barber, or whether you're just amusing yourself with me, we want to have one thing understood. I came here, sir, as a matter of courtesy to you, and you will have to treat me with just as much courtesy. Otherwise, I shall wish you good-morning." This was said with a flash of the eye which warned Radberg that, in his rather overbearing way, he was going too for. "Oh, my dear young friend," he replied, persuasively, "you don't understand. In Germany I am--well, perhaps what you would call a rather distinguished man. At least, my neighbors are good enough to say so. And, in Germany, when a herr professor talks, others listen respectfully." "Just the same way with the hair professors in this country," chuckled Jack. "When an American barber gets wound up and started, all a fellow can do is to listen. It's no use trying to run away from a barber anywhere, I guess. He has you strapped down to the chair." "Barber?" repeated Professor Radberg, in disgust. "I don't understand you." "Oh, it isn't necessary," laughed Jack. "It's a sort of Yankee joke. And I beg your pardon, Professor, if I am wasting your time. Now, go ahead, please, and tell me why you invited me here." There was something of salt water breeziness and crispness about Jack's speech that caused the German's brow to cloud for an instant. Then, after a visible effort to compose himself, Radberg leaned forward to ask: "Do you speak German?" "No, sir." Jack shook his head. "Ach, that is too bad!" muttered the German, in a voice suggesting severe disapproval of one who hadn't mastered his own native tongue. "However, you will soon learn." "Yes; if there's a big enough prize goes with it," agreed Jack. "Prize?" repeated Professor Radberg. "You will say so!" Then, leaning forward once more, and speaking in his most impressive voice, Herr Professor Radberg continued: