- Published: 1977
- Nebula Award for Best Novel, 1978 —
- Locus Award for Best Science Fiction Novel, 1978 —
A classic novel of man's future and fate, written by the eminent American physicist and award-winning author of Timescape. 2034. An indistinguishable sound is heard from the depths of space and one member of the search and survey team, Nigel, believes he knows its origins. 15 years earlier, he was the astronaut sent to implode a firey comet as it hurtled toward the Asian subcontinent. Once inside the fissure he made an unlikely discovery: an abandoned alien ship. Against his better judgment, Nigel carried out his mission, destroying the vessel-but not before clandestinely removing alien data and technology from on board. Now, as the team sets forth on a new adventure of discovery, Nigel's past will collide with the present, introducing him to wonders beyond human comprehension.