Jennifer Spencer (Sondra Locke
) and her little sister were gang raped years ago, after a female friend of the gang had persuaded them to come to the fair. The brutal rape left the sister permanently catatonic and almost vegetative. Jennifer is now out for revenge.
In the beginning of the film, Jennifer is seen with one of the rapists, George Wilburn (Michael Maurer
). It is early morning and she is with him in a car out on the cliffs. She pulls out a nickel-plated Colt Detective Special revolver and shoots him twice - one time in the groin and one time in the head at point-blank range, then leaves the scene.
Inspector Harry Callahan (Clint Eastwood
), in the meantime, is seen in a court room where he has brought a young blonde haired suspect named Mr. Hawkins (Kevyn Major Howard
) to trial. The case is dismissed as a travesty because Harry did not have the right to seize the evidence used to prove Hawkins guilty.
After insulting Hawkins in the elevator, Harry goes to his usual coffee diner and orders the usual black coffee. The waitress tries getting his attention by pouring massive amounts of sugar into his coffee and Harry, who is reading a newspaper, does not notice. As he walks out, he takes a sip of coffee and spits it out in disgust. As he returns to complain, he sees that the open signs were switched to closed. A robbery ensues but Harry stops it, going in the back way where he shoots up the gang of robbers. One is left alive and grabs the waitress as a human shield, but Harry points his .44 Magnum handgun revolver at him and dares the thug to shoot her in order for Harry to justify killing the thug ("Go ahead... make my day!"
) The police arrive shortly afterward when the robber drops his gun.
Meanwhile, Jennifer is at an art exhibit where some of her paintings are put on display, but she claims to the owner that she must miss it because she needs to visit someone up north. She goes to the hospital to visit her sister Elizabeth (Lisa Britt
), whom the doctor says is in a permanent vegetative state. Jennifer tells her sister of what she did to George Wilburn and then leaves.
Later that night, Harry is at a mobster named Threlkis's granddaughter's wedding party. Harry antagonizes Threlkis (Michael V. Gazzo
) in front of his own granddaughter, accusing him of killing a young hooker. Threlkis freaks as Callahan pulls out papers where he claims the hooker may have confessed everything, and he dies of a heart attack right at the table. Harry walks away and it is revealed that the papers are blank.
The following day, Callahan and the rest of the cops are investigating the car containing the deceased George Wilburn in it. Shortly afterwards, Callahan is talking to his superiors, Captain Briggs (Bradford Dillman
), Lt. Donnelly (Michael Currie
), and the Chief (Bill Reddick
). He is lectured about how he handled the Threlkis case, and Callahan is defensive on how that case was his to handle. His superiors demand that Callahan relax and take a vacation.
After Callahan leaves a restaurant that night, he is attacked by four of Threlkis's hitmen. After killing three of them, one escapes in his car. Lt. Donnelly then orders Callahan to not be so reckless and demands he take a break with "peace". Out in the forest, Callahan practices shooting with his brand new .44 Automag handgun, a powerful .44 caliber semi-automatic pistol which fires more rapidly and accurately than his .44 Magnum revolver. His friend Horace King (Albert Popwell
) shows up shortly afterwards to talk to him, convincing him he has the best place for Callahan to go for a vacation.
Driving home late at night, Callahan is attacked by Hawkins and his friends, who try to kill him with a Molotov cocktail. Harry manages to get out of his car, and throws the cocktail into Hawkins' car, causing him to drive off a pier into the water, where Hawkins and his friends drown.
Lt. Donnelly sees that this is the last straw and orders Callahan to investigate the Wilburn killing in his hometown. Callahan reluctantly agrees and is sent on "vacation" to the town San Paulo, a coastal resort town down the California coast. What he does not know is that Jennifer Spencer has also gone down to San Paulo to fully exact revenge on her rapists, who live there. Her story for staying at San Paulo is that she's renewing the carousel house and painting the merry-go-round horses at the fairgrounds. While walking on the beach at the fairgrounds, there is a flashback of Jennifer's rape and it is shown what actually happened 10 years ago right on the beach near the fairgrounds.
During the time in San Paulo, Callahan receives a bulldog named Meathead from his friend Horace. He also stops a bank robbery in progress when he arrives, and he saves the life of young Officer Bennett (Mark Keyloun
). While taking his dog, Meathead, for a walk, he runs into Jennifer (who falls off of her bicycle when Meathead barks at her). Unaware of each other's true identity, the two have a brief exchange of words and then part. At night, Callahan walks into a bar for a beer and meets the malicious Ray Parkins (Audrie Neenan
), a butch lesbian. After insulting Ray, Callahan demands to know if anyone knows George Wilburn. When he tells how Wilburn died, Ray just starts a raucous laughter which pursues to a laugh riot.
The next morning, another rapist, Kruger (Jack Thibeau
) goes fishing at the beach. Jennifer follows him. She steps in front of Kruger, who recognizes her right before she shoots him in the groin. She then shoots him in the head, and he falls over in his chair. When his body is reported to the cops, Callahan shows up only to be shooed away by Chief Lester Jannings (Pat Hingle
) for continually interfering with the San Paulo's police job. At the station, Callahan asks Bennett to find out anything he knows about the case. Harry finds a picture of Jannings's son Alby's friends on the wall, and he has Bennett investigate that too. At dusk, Callahan stops by Mrs. Kruger's (Nancy Parsons
) fish market to question her about the Wilburn and Kruger murders, only to be kicked out after brawling with her brothers Eddie (Russ McCubbin
) and Carl (Robert Sutton
Callahan is attacked by the surviving hitman who was hired by Threlkis, but manages to shoot him in advance after being tipped off to his presence by Meathead.
Ray eventually talks to Tyrone (Wendell Wellman
), another rapist, about what is happening. Tyrone disregards her warning and tells her to leave his store. Later that day, Tyrone is confronted by Jennifer in his garage. He tries to reason with her as she steps closer, her gun drawn. Realizing she isn't standing down, Tyrone grabs for his own gun, at which point Jennifer guns him down.
Callahan meets up with Jennifer again, this time at an outdoor restaurant. The two talk again in a more polite manner and converse about the murders. Upon hearing Callahan is a cop, Jennifer becomes worried that he is on to her.
Now with Wilburn, Kruger and Tyrone dead, Ray calls Mick (Paul Drake
), the leader of the rapists, to come down for help from Las Vegas where he lives. When Callahan finds Tyrone's body, he heads over to Ray's house at night and sees Jennifer's car parked out front. Jennifer hides, and Callahan goes inside to find Ray. Mick attacks Callahan, and after a brawl, Callahan takes Mick away. Once they are gone, Jennifer sneaks into the house and confronts Ray. Ray sips a soda, and asks her, "So tell me, how's your slut sister?" Jennifer replies by shooting her in the heart, and then in the head.
Meanwhile, Mick is bailed out by Eddie and Carl while Callahan returns to Ray Parkins's house only to find the woman dead. Horace is seen driving up to Callahan's motel that same night to visit him he is carrying his powerful shotgun and some alcohol. Upon arrival into Callahan's room, Horace is greeted by Mick, Eddie and Carl, who slit his throat and steal his shotgun.
After buying a few beers, Callahan meets up with Jennifer late at night by the pier. The two talk and this time Jennifer invites Callahan up for a drink at her place, where he sleeps with her. After a brief sleep, Harry gets out of bed when it is still dark. In the garage he sees Jennifer's car and recognizes it as the one that was parked at Ray's house before. Harry goes to Mrs. Kruger's fish market after Officer Bennett informs him that Eddie and Carl bailed Mick out.
As Callahan leaves after receiving no cooperation from the hostile Mrs. Kruger, he is ambushed by Mick, Eddie and Carl on a pier. A melee ensues with Callahan being viciously beaten and dumped into the water... his .44 Magnum handgun lost.
Jennifer is then seen going to Janning's house to eliminate Alby (Matthew Child
). She prepares to kill Alby only to find out that Alby is in a vegetative state just like her own sister. Jennifer is stopped cold by Jannings, who orders her to drop her gun. After doing so, Jannings explains how he covered up the rape because he was a public figure, and the guilt drove Alby insane which caused him to crash his car into a wall, rendering him a mute quadriplegic. Suddenly, Mick arrives with Eddie and Carl who take Jennifer hostage with her own weapon. As they are starting to leave, Mick shoots and kills Jannings with Jennifer's gun when Jannings tries to pull out a gun. He assures Eddie and Carl that it's a "freebie".
As this is happening, the bloodied and battered Callahan returns to his motel room to find Horace's dead body, and Meathead limping after being attacked by Mick and his gang. Enraged, Callahan opens his drawer, and prepares his replacement weapon: his powerful .44 Automag handgun. He then leaves to find and kill the thugs responsible.
Mick, Eddie, and Carl set to gang-rape Jennifer again at the same fairground where she was raped a decade earlier. After a struggle, Jennifer escapes and runs through the deserted fairground and seeks shelter in the carousel where she turns it on and hides in it. Fleeing from the merry-go-round, Jennifer runs out followed by Mick, Eddie and Carl, but Callahan's silhouette appears on the boardwalk... armed with the large .44 Automag. While Eddie and Carl are quickly taken down, Mick grabs Jennifer as a shield. With nowhere left to go, Mick forces her up onto the Giant Dipper roller coaster and Mick taunts Callahan, as he holds his gun on Jennifer. Harry repeats the phrase he said earlier in the diner holdup, "Go ahead, make my day." Mick gets too cocky, and Jennifer quickly punches him, giving Callahan a clear opening. He fires off four rounds, which all hit Mick. Mick stumbles backwards, crashes through the support railing and falls onto the still operating carousel, and is impaled on a unicorn's horn.
Justice is finally given to Jennifer at the end of the movie. When asked by Officer Bennett about the revolver found on Mick's body... the one belonging to Jennifer... Callahan lets Mick be misidentified as the killer. He tells Bennett the gun ought to be run through Ballistics; he thinks it's the gun that killed the Chief. He knows that once Ballistics compares the bullets from Jannings, Tyrone and Kruger, Mick will be blamed for all the murders and the police will close the books on them, thus safeguarding Jennifer. As the camera pulls back, Harry and Jennifer walk slowly away down the boardwalk.