Science fiction masters Larry Niven (Ringworld) and Gregory Benford (Timescape) continue the thrilling adventure of a human expedition to another star system that is jeopardized by an encounter with an astonishingly immense artifact in interstellar space: a bowl-shaped structure cupping a star, with a habitable area equivalent to many millions of Earths. And which, tantalizingly, is on a direct path heading toward the same system the human ship is to colonize.

Audacious astronauts encounter bizarre, sometimes deadly life forms, and strange, exotic, cosmic phenomena, including miniature black holes, dense fields of interstellar plasma, powerful gravity-emitters, and spectacularly massive space-based, alien-built labyrinths. Tasked with exploring this brave new, highly dangerous world, they must also deal with their own personal triumphs and conflicts.

In a future wracked by environmental catastrophe and social instability, physicist John Renfrew devises a longshot plan to use tachyons - strange, time-traveling particles - to send a warning to the past. In 1962, Gordon Bernstein, a California researcher, gets Renfrew's message as a strange pattern of interference in an experiment he's conducting.

After more than two hundred years as a corpsicle, Jaybee Corbell awoke in someone else’s body and under threat of instant annihilation if he made a wrong move while they were training him for a one-way mission to the stars. But Corbell bided his time and made his own move. Once he was outbound, where the society that ruled Earth could not reach him, he headed his starship toward the galactic core.

The gigantic comet had slammed into Earth, forging earthquakes a thousand times too powerful to measure on the Richter scale, tidal waves thousands of feet high. Cities were turned into oceans; oceans turned into steam. It was the beginning of a new Ice Age and the end of civilization. But for the terrified men and women chance had saved, it was also the dawn of a new struggle for survival--a struggle more dangerous and challenging than any they had ever known....