He looked with new eyes at the instrument panel under the forward port and was astonished at the crudity of the engines it controlled. He was primarily an astrophysicist, and his understanding of atomic propulsion had been negligible; now its every function was clear to him at a glance. Experimentally he drew a graph of the arc he described through space, and knew to a minute how long it would be before the braking jets slowed his speed for landing. He raised his eyes to the forward port where the ruddy disc of Mars hung framed against the black velvet backdrop of space like a red jewel burning dully among a random display of lesser brilliants, beckoning him on with the future's illimitable promise. * * * * * He sat quite still for a time on the padded control couch, thinking intently, testing the new powers of his mind as he might have flexed a newly discovered limb. His first conclusion was inescapable: his Tenant had left him because It could not exist outside Earth's gravity. It had been forced to quit him or perish, and Its departure had made him the first really free man. They were not invincible. They were not even particularly intelligent, in spite of Their gift of parasitic control, or his own Tenant would have known Its danger. The fact that They were gravity-bound entities gave him the first vulnerable chink in Their armor, an Achilles heel that offered eventual salvation for men. There would be other ways to be rid of Them, and it was his responsibility as the first free man to see that others of his kind were freed as he had been. He pictured the harmonious integration of an Earth peopled by free men and saw clearly the heights men might reach unhampered by their Tenants. His own possibilities, when he had summed them up, awed him in their extent. There were no limits to what he could do, no bounds to the knowledge he could accumulate and use. _This is what being a man is really like. I can liberate a world. Like Moses, I can set my people free._ The thought set his face shining, suffused him with a glow of anticipated triumph. It was all so simple, now that he was free.... In a few hours he would land on Mars, and in a matter of minutes he could set up a beam transmitter to report back to the scientific foundation that had sent him out. He could not tell his fellows the truth because they were still captive, and their Tenants must not be warned; but he could invent a plausible story of easily acquired wealth on Mars that would bring other and larger commercial expeditions swarming after him. With the help of other freed men he could found a new civilization on the red planet, develop means to carry the fight back to Earth and exterminate the Tenants utterly. It would take time, but in the end men would be free.