A man dressed in black drives through Los Angeles, and flashes back to a girl dying in a car accident. The man arrives at an apartment complex, and kills a female tenant (who recognizes him) with a drill. Afterward, the man dons a ski mask, and murders two other women, the first with a hammer, and the second with a screwdriver. The police are called, and they interview the people who found the bodies, as well as Vance Kingsley, the owner of the building. The next night, the killer strikes again, breaking into the apartment of a woman who is masturbating in her bathtub, and shooting her in the stomach and head with a nail gun. The murderer then abducts Laurie Ballard, a fifteen-year-old who lives in the above apartment with her family.
Laurie's brother Joey is questioned by Detective Jamison, and frustrated by the detective's seemingly lax attitude towards Laurie's disappearance, decides to search for his sister on his own. While looking through the homes of the murdered women, Joey meets up with Kent, Vance's nephew, who has been hired to clean up the apartments of the deceased tenants. While Joey is helping Kent, Kathy Kingsley, Kent's cousin and Vance's daughter, is brought up, with Kent mentioning that Vance has not been the same since Kathy died in a car accident.
It is revealed that Vance is the serial killer, having been driven insane and to religious mania by the death of his daughter. He is killing sinners, and has kidnapped Laurie (who is kept tied up in Kathy's bedroom) to replace Kathy. During a discussion with Detective Jamison, Joey realizes that all the clues point to Vance being the killer, so he goes to the Kingsley house, and is followed there by Kent (who had earlier seen the bound Laurie in his uncle's home). Joey finds bloody tools in Vance's garage, and is confronted by Kent, who sets Joey on fire to protect his family.
Kent walks in on Vance talking to Laurie, and enrages his uncle by telling him that he and Kathy had an incestuous relationship. Vance and Kent fight, and Kent ends up fatally stabbing Vance with a kitchen knife. Kent goes to Laurie, cuts her bonds, and rapes her. Afterward, Kent acts as if he and Laurie are married, and implies that he killed Joey and Vance, prompting Laurie to stab him to death with a pair of scissors. A dazed and bloodied Laurie wanders out of the house, as an intertitle states that the film was a dramatization of events that occurred in 1967, and that Laurie was institutionalized for three years, and now resides in San Fernando Valley with her husband, and their child.
Who is Vance's nephew?
Kent