The book's main character, Alan Gregory, is a clinical psychologist in private practice. The primary story line begins during a session with a former marital therapy patient who has just requested an individual session after a lengthy absence from treatment. She announces that her husband may be a murderer—and not just a common, everyday murderer, but a sexually motivated serial killer of women. She wants the psychologist to get the police involved. Dr. Gregory is primarily assisted in unraveling the resultant psychological and legal knots by another main character, Sam Purdy, who is a close friend and a police detective.