A news broadcast details an increase in crime in Los Angeles. At his new home, Paul Kersey's maid, Rosario, is preparing dinner. Paul seems to have picked up the pieces of his New York life and moved on, now dating KABC news/radio reporter Geri Nichols. They go to pick up Paul's daughter Carol from the hospital. Her doctor says that despite traumatic catatonia, Carol has begun to speak again. Paul, Geri, and Carol spend the afternoon at a carnival. While waiting in line for ice cream, Paul gets mugged by Nirvana's Gang. He catches up with Jiver who denies taking Paul's wallet and then Paul beats him up. Geri heads to do an interview with a senator while Carol and Paul go on a boat ride. The members of Nirvana's Gang come to his house, where they rape Rosario. Paul arrives home and is beaten unconscious. Rosario tries to call police, but the members of the gang kill her. They take Carol with them and PunkCut rapes her. She jumps from a window, becoming impaled on a railing. Paul regains consciousness as Geri and the police arrive. Lt. Mankewicz asks for help identifying the muggers. Paul learns about the death of his daughter. He views mug-shot photos at the station, but says, "It won’t do any good." After the funeral, Paul takes a handgun kept hidden in his closet. He rents a low-rent apartment in the inner city. The next night, he spots Stomper and follows him into an abandoned building as a drug deal is about to be made. Paul kills one of the men, then orders the others out and kills Stomper. The next night, patrolling the streets, he hears a scream from a man and a woman being assaulted. One of the muggers is Jiver, the member of Nirvana's Gang he chased the day of his daughter’s death. He kills two. Jiver is wounded, but he and a fourth mugger get away. Paul follows a trail of blood and kills Jiver at a warehouse. The L.A. police hear about these murders, as does New York's. Paul falls under suspicion and Lt. Frank Ochoa is called by the LAPD to help. Fearing that Paul, when caught, will reveal that the cops let him go instead of prosecuting, the NYPD sends Lt. Ochoa to make sure that does not happen. Lt. Ochoa meets with Lt. Mankewicz, who suspects Lt. Ochoa is hiding something. Lt. Ochoa breaks into Geri’s apartment and tells her about Paul's past and present vigilante sprees. Geri confronts Paul but he denies it, ascribing the tale to Lt. Ochoa's imagination. Paul drives Geri to work. Lt.Ochoa follows Paul to a local square where Paul spots the three remaining members of Nirvana's Gang who attacked him: Cutter, Punkcut and Nirvana. Paul follows the trio on a bus to an abandoned park, where a drug deal goes down. Lt. Ochoa follows and decides to help Paul when the criminals are about to spot him. Lt. Ochoa is shot by Nirvana. Paul manages to kill Cutter who vainly tries to shield his head with a boom box. Punkcut is also wounded. Paul kills the getaway driver and weapons dealer, who's car plummets off a cliff and explodes. The leader of Nirvana's Gang, Nirvana, gets away. Paul goes to Lt. Ochoa and asks why he saved his life. Lt. Ochoa felt it better to side with Paul than these criminals. He tells Paul to kill Nirvana for him, then Lt. Ochoa dies as the police arrive and Paul escapes the park. The police get the name of Lt. Ochoa’s killer from a badly injured Punkcut before he dies. Paul later learns, from one of Geri's colleagues at KABC, that the police are preparing SWAT team to take down Nirvana. Paul also obtains a police scanner and begins monitoring the police radio traffic, and shortly finds out when and where the arrest of Nirvana is taking place. He goes to the same location to exact his own justice on Nirvana before the police can arrest him but he is not successful. Nirvana (real name Charles Wilson) runs when he sees the police approaching. He gets tazed but with no effect due to an influence of PCP. He is finally arrested after stabbing several officers and slashing Paul on the arm during a chase. Tried and found criminally insane, Nirvana is sent to McLarren State Hospital. Geri and Paul visit, requesting an interview with Nirvana, but are turned down. The visit allows Paul to steal a doctor's ID card. Paul proposes to Geri the next day and she accepts. That night, Paul uses his fake ID at the hospital and confronts Nirvana. Nirvana and Paul get in a violent fight and Paul is stabbed repeatedly with a scalpel. But when Paul ducks a punch, Nirvana's hand smashes through a machine and Paul turns up the power, electrocuting Nirvana to death. Donald Kay, an orderly on duty, witnesses Nirvana's death but he sympathizes with Paul and gives him three minutes to escape before sounding the alarm. Geri goes to Paul's apartment where she finds a scanned copy of the stolen ID. She realizes that Paul is actually the vigilante that Lt. Ochoa claimed him to be, hearing a report of Nirvana's death on the radio. She places the paper and engagement ring on the table and drives off. Paul arrives home to an empty apartment. A few months later Paul is speaking to his boss about a new architectural design. His boss Elliott Cass invites him to a party, and when Paul is asked if he's free, he answers: "What else would I be doing?"
- Charles Bronson as Paul Kersey
- Jill Ireland as Geri Nichols
- Vincent Gardenia as Lt. Frank Ochoa
- Anthony Franciosa as Police Commissioner Herman Baldwin
- Robin Sherwood as Carol Kersey
- Laurence Fishburne as Cutter
- Charles Cyphers as Ronald Kay
- Thomas F. Duffy as Nirvana
Issac Hayes was reccomended along with the producers of the film to compose the score; however, Michael Winner chose former Led Zeppellin guitarist Jimmy Page (who was Winner's neighbour at the time). The opening credits bear Page's signature guitar tone, along with the heavy reverb-laden drum sound that he used with Led Zeppelin. The film's soundtrack was released in February 1982.