Holden threw off his shoes and coat and tumbled into the berth. The events of the last weeks were spinning in his head, and a procession of visions passed before his eyes. That terrible catastrophe, the trip to Europe, to the capitol of the World Union, and now, the appointment as leader of the most important expedition in the history of the universe, with the possible exception of that first epoch-making voyage to Mars back in 2350. Another vision appeared before his eyes. Jean! Jean, his own sweetheart, the one person in the world who mattered, gone now for a full year. Why had she decided to make the voyage to Mars? What could have happened to the ill-fated _Gloriana_, with her hundreds of passengers and valuable cargo? A year ago she had left; and, as some people said, merely drifted out into space, never to be heard from again. A deep sob shook Holden's body as he thought of that beautiful girl, who, laughing at his fears, had stepped into the space flyer with a smile on her lips, promising to come back in a year and marry him. At last, however, these memories gave way before exhaustion, and he fell into a sleep, troubled by strange dreams. It seemed that a great serpent had attacked him, and, flinging its coils about his body, was slowly squeezing out his life. Suddenly, he was wide awake. Strong hands were on his throat, the thumbs were pressed tight against his larynx. He struggled to gain his breath, to shout for help, but the pressure closed his throat. In another moment it would be too late. Then his mind cleared; raising both hands to the back of his neck, he grasped the little fingers of his assailant, and pulled with all his strength. The man gave a cry of pain and anger and relaxed his grip. Holden gulped in a breath of air, and flung himself from his berth, endeavoring to catch and hold the coward who had attacked in the dark. The man, however, was wiry and quick. With a sudden jerk he wriggled loose, gained the door and was gone. When Holden reached the corridor, no one was in sight. Quickly he walked to Professor Erickson's room, awakened him, and told him what had happened. Erickson rang up a steward, who promised to do everything in his power to apprehend the culprit. "Who could it have been?" asked Erickson. "I haven't the slightest idea. I have no enemies that I know of. I'm not carrying any valuables. It was probably a case of mistaken identity." The incident was dismissed with that interpretation, and it was several weeks before Holden thought of it again, but then he wished fervently that he had investigated more thoroughly. CHAPTER II A Midnight Attack It was midnight when the liner reached San Francisco, but Holden insisted on going at once to the offices of the Interplanetary Transportation Company, where work was carried on day and night. Fortunately they found an official of the company who had sufficient power to carry out their instructions.