For Detective Sergeant Alicia Aldrich, a homicide investigator for the California State Police, it begins with the body of a nondescript man, brutalized and dumped in the desert near San Bernardino. Soon after, there are other murders, linked together in a bizarre pattern. A gruesome "souvenir" has been taken from each victim and their bodies have been oddly tattooed. Even stranger, their blood contains a substance found only in the blood of astronauts. The killer has made contact with Aldrich -- teasing her with pieces of a puzzle whose origins are mysteriously found among the stars. Is she dealing with a psychopath driven by delusions of UFOs, alien abductions, and extraterrestrial conspiracies? Or is the killer in fact an unearthly force unlike any the world has ever seen? And where does Aldrich herself fit into this terrifying mystery? For what purpose -- human or inhuman -- has she been chosen to witness the killer"s most horrifying act of all?