Then the door of the cabin where Tom Swift and his friends were was suddenly burst open, and seven or eight men threw themselves within. They were led by a man with a small, dark mustache and a little tuft of whiskers on his chin--an imperial. He looked the typical Frenchman, and his words, snapped out, bore out that belief. What he said was in French, as Tom understood, though he knew little of that language. Also, what the Frenchman said produced an immediate result, for the men following him sprang at our friends with overwhelming fierceness. Before Tom, Ned, Captain Warner, Mr. Damon or Lieutenant Marbury could grasp any weapon with which to defend themselves, had their intentions been to do so, they were seized. Against such odds little could be done, though our friends did not give up without a struggle. "What does this mean?" angrily demanded Tom Swift. "Who are you? What are you doing aboard my craft? Who are--" His words were lost in smothered tones, for one of his assailants put a heavy cloth over his mouth, and tied it there, gagging him. Another man, with a quick motion, whipped a rope about Tom's hands and feet, and he was soon securely bound. In like manner the others were treated, and, despite the struggles of Mr. Damon, the two government men and Ned, they were soon put in a position where they could do nothing--helplessly bound, and laid on a bench in the main cabin, staring blankly up at the ceiling. Each one was gagged so effectively that he could not utter more than a faint moan. Of the riot of thoughts that ran through the heads of each one, I leave you to imagine. What did it all mean? Where had the strange men come from? What did they mean by thus assaulting Tom and his companions? And what had happened to the others of the crew--Koku, Jerry Mound, the engineer, and George Ventor, the assistant pilot? These were only a few of the questions Tom asked himself, as he lay there, bound and helpless. Doubtless Mr. Damon and the others were asking themselves similar questions. One thing was certain--whatever the stowaways, as Koku had called them, had done, they had not neglected the Mars, for she was running along at about the same speed, though in what direction Tom could not tell. He strained to get a view of the compass on the forward wall of the cabin, but he could not see it. It had been a rough-and-tumble fight, by which our friends were made prisoners, but no one seemed to have been seriously, or even slightly, hurt. The invaders, under the leadership of the Frenchman, were rather ruffled, but that was all. Pantingly they stood in line, surveying their captives, while the man with the mustache and imperial smiled in a rather superior fashion at the row of bound ones. He spoke in his own tongue to the men, who, with the exception of one, filed out, going, as Tom and the others could note, to the engine-room in the rear.