Grant saw the quick movement of the other toward an open side flap. He did not hesitate an instant. His fist shot out and caught the Ganymedan flush in the throat, while his left hand simultaneously seized the creatoid-covered arm that gripped a pencil-ray. The helmeted head went back with a sickening thud. But the Ganymedan was a powerful brute. Even as he staggered back from the force of the blow, vainly trying to release the pencil-ray for action, his right foot jerked forward. The next moment both were rolling on the floor, twisting and heaving in silent combat. Frightened passengers rushed down the corridor, screaming with terror, half carried along by the hurricane wind, clambering over the combatants in an insane desire to get away, where, they knew not; and still neither relaxed his grip, seeking a mortal hold. Pemberton was certain that his silent unknown foe held the clue to the mystery he was trying to fathom. He fought on, silently, grimly. The cold creatoid fabric was slippery, but a sudden jerk of an arm, a certain quick twist that Grant was familiar with, and his enemy went limp. Grant's breath was coming in quick, labored gasps. There was very little air left now. But he did not care. He tugged at the fastenings on the helmet. He must see who his captive was, wrest from him the heart of the mystery. There came a clatter of feet behind him, a sudden rush of space-suited figures that overwhelmed and passed over him with trampling strides. He was torn loose from his prey, rolled over and over, gasping for air. When he staggered to his feet again, bruised and shaken, the corridor was swept clean of figures. His assailants had carried his opponent away with them. A wild surge of anger swept through him. More Ganymedans, these rescuers, all accoutered for airless space. They had been carefully prepared for this. Heedless of all else, he swayed groggily after them, intent only on joining battle once again. The illumination was dim now, the cries of fear that had rung through the ship were gone; only a deathly silence reigned now. His lungs were burning for want of air; even the whirlwind had died down for lack of fuel. But still he kept on, like a bloodhound on the trail. * * * * * He rounded a corner. A slight figure, swaying like a reed, collided with him and would have fallen if he had not thrust out a supporting arm. It was a girl. Even in the shadowy light he saw that she was beautiful. Her delicately molded features were drained white, but her deep pooled eyes were level in their gaze, unafraid. "I'm sorry," he managed, finding utterance labored, "Are you hurt?" "Quite all right," she said, with a wan smile, "if only I had some air to breathe." The essential bravery of her touched him. He forgot all about the escaped Ganymedans. "We'll have to try some other portion of the ship. Maybe some of the bulkheads are uninjured."