2570 Earth is transformed. A mere billion people are supported by advanced technology on a world that is almost indistinguishable from the natural, with recovered forests, oceans, ice caps. It is not an age for expansion; there are only small science bases beyond the Earth. But this is a world you would want to live in: a Star Trek without the stars. After 500 years the Kernel returns, and a descendant of Stoney, who Malenfant will call Emma II, mounts a mission to see what became of Malenfant. She finds him still alive, cryo-preserved . . . His culture-shock encounter with a conservative future is entertaining . . . But the Kernel itself turns out to be attached to a kind of wormhole, through which Malenfant and Emma II, exploring further, plummet back in time, across five billion years . . .