Paul Kersey (Charles Bronson) seems to have picked up the pieces of his life and moved on, and is now dating L.A. radio reporter Geri Nichols (Jill Ireland). They go to pick up Kersey's daughter Carol (Robin Sherwood) 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 is pick-pocketed by five gang members: Nirvana (Thomas F. Duffy), PunkCut (E. Lamont Johnson), Stomper (Kevyn Major Howard), Cutter (Laurence Fishburne) and Jiver (Stuart K. Robinson). He catches up with Jiver, who denies taking Paul's wallet. Paul lets him go.
Geri leaves to do an interview while Carol and Paul go on a boat ride. The five gang members break into Paul's house and gang rape the maid, Rosario (Silvana Gallardo), then wait for Kersey. When Paul arrives home with his daughter, he is beaten unconscious. Rosario tries to call the police, but a mugger hits her with a crowbar, killing her. They kidnap Carol, take her to their hideout, and begin to rape her. She jumps through a window in an attempt to escape, and dies after impaling herself on railings below.
When the police arrive, Lt. Mankewicz (Ben Frank) asks for help identifying the muggers, but Paul refuses. After the funeral, he takes a .380 Beretta 84 handgun to a low-rent inner city apartment as a base of operations. The next night he spots Stomper and follows him into an abandoned building as a drug deal is about to be made. Kersey kills one of the dealers, then orders the others out and proceeds to execute Stomper. The following night, patrolling the streets, he hears a scream from a couple being assaulted by several muggers in a parking garage. One of the muggers is Jiver. Paul intercedes, killing two and wounding Jiver. Paul follows Jiver's blood trail and shoots him in the head with a .45 M1911A1 pistol.
The LAPD and NYPD hear about the murders. When Kersey falls under suspicion, NYPD Detective Frank Ochoa (Vincent Gardenia) is called in for fear that Kersey, when caught, will reveal that he was let go instead of prosecuted. Ochoa meets with Lt. Mankewicz, who suspects Ochoa is hiding something. Ochoa breaks into Geriâs apartment and tells her about Paul's vigilante spree. Geri confronts Paul but he denies it.
Ochoa follows Kersey to a local square where Kersey spots the three remaining gang members. He follows them to an abandoned park, where a major arms and drug deal goes down. Ochoa decides to help Paul when the criminals are about to spot him. Ochoa is shot, while Paul kills Cutter and severely wounds PunkCut. Paul kills the getaway driver and the seller of the firearms, who plummet off a cliff. Nirvana gets away. Ochoa tells Paul to kill one for him, then dies as the police arrive. Paul flees while PunkCut dies from his injuries.
Paul later learns, from one of Geri's colleagues, that the police are preparing a tactical unit to capture Nirvana. Paul obtains a police scanner and, by monitoring police radio traffic, finds out when and where the arrest is going to take place. He drives to the location. Nirvana is tasered, but with no effect due to the 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, he is sent to a mental institution. Geri and Paul visit him, requesting an interview, but are turned down. While there, Paul steals a doctor's ID card. The next night, Paul uses his fake ID to confront him. They fight and Paul is stabbed repeatedly with a scalpel. Nirvana's hand smashes through an electroshock machine. Paul turns the power on, fatally electrocuting him.
Geri goes to Paul's apartment, where she finds evidence of his making a fake ID. Upon hearing a news report of the hoodlum's death on the radio, she realizes that Paul really is the vigilante Ochoa claimed him to be. She places her engagement ring on the paper, packs her things, and drives off. Paul arrives home to an empty apartment.
A few months later, Paul is speaking about a new architectural design. His boss invites him to a party, and when Paul asked if he's free to attend, he answers: "What else would I be doing?". We next see a shadowy figure walking in the night (presumably Kersey) continuing the vigilante hunt.
Paul's boss invites him to where?
A party