In A.D. 2001 the computer on board the United States Spaceship Discovery, en route to Jupiter's moons, malfunctioned. Grappling frantically with the broken air hose of his spacesuit, Frank Poole had died in space. In A.D. 3001 his perfectly preserved body is retrieved. Technologies restore his life and Frank becomes a telepathic, machine-assisted inhabitant of the fourth millennium, with a lot to learn.