Dan Carter is a San Diego homicide detective who, due to a personal tragedy, has become obsessed with tracking and catching serial killers. The book follows four of his cases. The first is about a true psychopath who is called "The Assassin." The Assissin uses a high powered rifle to kill his victims. Before leaving San Diego, he cripples Dan with a shot in the back. This case is revisited several times between the other three cases.The perpetrator in the second case is called "The Tourist Killer." He is an antisocial personality disordered individual who takes his victims into Mexico to kill them. He meets his demise at the hands of his wife who is fed up with his abuse.The murderer in the third case is a schizophrenic man whose dead aunt drives his killing spree. He kills his victims by cutting the spinal cord at the level of the first or "axis" vertebrae and is thus known as "the Axis Killer."The fourth case is about a delusional person who kills for a perceived need for revenge against the police. This killer is known as "the Revenge Killer." The book concludes after Dan chases "The Assassin" over a cliff.The antagonist's obsession for catching serial killers is gradually replaced by love for his beautiful, blond, Swedish, physical therapist. The story follows the couple from their introduction to the development of a romantic relationship,