"Then come back to the hotel with me." "You are a foreigner, aren't you?" asked Jack, surveying the stranger coolly. "I am German," replied Radberg, in a tone of surprise. "I thought so," nodded the boy. "That is, I didn't know from what country you came. But, in this country, when we ask a favor of a stranger, we usually say 'please.'" "I am Herr Professor--" "Oh, barbers are just as polite as other folks," Jack assured him, his laughing eyes resting on the somewhat bewildered-looking face of the German. "Then please, Herr Benson, come back to the hotel with me." "Yes; if it's really necessary. But why do you want to go to the hotel?" "Because, Herr Benson, when we are there, I shall have much of importance to say to you." "Important to me, or to you?" asked Jack, thoughtfully. He had no intention of answering a much older man disrespectfully. But there was about Herr Radberg the air of a man who expects his greatness to be recognized at a glance, and who demands obedience from common people as a right. This sort of thing didn't fit well with the American boy. "Oh, it is important to you, and very much so," urged the Professor, somewhat more anxiously. "Besides," added the German, with a now really engaging smile, "I have met your demand, Herr Benson, and have said 'please.'" "Then I suppose I'll have to meet your demand," nodded Jack, good-humoredly. "Lead the way, sir." "Ach! You may walk at my side," permitted the German. It all seemed a bit strange, but Captain Jack Benson had been through more strange experiences than had most Americans of twice or thrice his age. Besides, as he walked beside Herr Professor Radberg Jack imagined that he had guessed at least an inkling of the other's business. The German had announced himself as a professor; probably, therefore, he was a scientist. Being a scientist, the Professor had very likely invented, or nearly invented something intended for use in connection with submarine torpedo boats, and wanted to interest the concern by which the young submarine skipper was employed. Though this guess was a reasonable one, it soon turned out to be the wrong one. The Professor's real reason for seeking this interview was one that was bound to take the submarine boy almost off his feet. Readers of the preceding volumes in this series need no introduction to Captain Jack Benson, nor to his chums, Hal Hastings and Eph Somers. Such readers recall, as told in "_The Submarine Boys on Duty_," how Jack and Hal drifted into Dunhaven just at the right moment to fight for an opportunity to work themselves into the submarine boat building business. How the boys helped build the first of the now famous Pollard submarines, and afterwards learned how to man her, was all told, together with all their strange adventures in their new life.