Gavin looked at the chief engineer blankly. "You mean," asked Y of Villanowski, "that you and Murdock are working for the same organization?" The chief engineer laughed bitterly. "We're not working for anyone, but ourselves. You forget, Mr. Y, that the four-dimensional drive isn't the only contribution I've made to interplanetary travel. General Atomic stole the others. We had hoped—" he jerked his head at Gavin "—to keep this one for ourselves!" Gavin's mind was going in circles like a dog chasing its tail. What was Villanowski's motive? "Go on," said Y in a foreboding voice. Villanowski looked down at his chains. "A ship travels through space during a passage of time. It had occurred to me that if I could invert the formula and drive a ship through time during a passage of space, the crude rocket ships could be abandoned. Murdock had gotten in trouble when Transplanet was discovered to be a colonal smuggling ring. He had studied astrophysics under me at New Yale. I knew him and knew I could trust him." Gavin swallowed and struggled to keep a grip on himself. Obviously Villanowski had something up his sleeve. Villanowski looked at Gavin. "We needed a space ship to complete our experiments. The effect of the drive on a body at rest was startling enough to predict success if we could attain sufficient velocity." Gavin thought he detected a faint stressing of the word "startling". Villanowski had said, "The effect of the drive on a body at rest was startling...." The Nova was at rest! "I persuaded Cabot," Villanowski proceeded, "to let me install the mechanism aboard the Nova. Murdock was to try—" Gavin jumped. With a back-handed, edge-on swipe, he caught Y in the throat full on his larynx. Nadia screamed as Y went over backwards and lay still. The factor leaped to his feet. Gavin kicked him in the belly. Spinning against the girl, he wrenched out of her hand the dart-gun which she was drawing. "The keys!" Villanowski panted. "Y has them." Nadia opened her mouth to scream again. "Don't." Gavin pointed the dart-gun straight at her open mouth. Nadia shut it. The factor was writhing on the deck, but Y lay like dead. Gavin found the keys and released Villanowski. "The engine room," he cried, "we've got to reach the engine room." "Take Y's gun," said Gavin. He turned on Nadia. "Come along. We can't leave you here to sound an alarm." Nadia's lips were bloodless. She moved stiffly between them, Gavin's dart-gun prodding her gently in the spine. They reached the engine room without being discovered and disarmed the startled guard. Villanowski whistled a bar in C sharp and then said, "Open sesame." The door in the steel bulkhead swung soundlessly outward.