In Sherwood, Ohio, three debutantes, all named Heather, represent the most popular clique at Westerburg High School. A fourth member of the circle, Veronica Sawyer, is wary of the Heathers’ misdeeds, but she follows along to preserve her social status. In the cafeteria, the girls’ leader, Heather “Number One” Chandler, orders Veronica to write a love note to an obese schoolmate named Martha “Dumptruck” Dunnstock, copying the handwriting of football player Kurt Kelly. Reading the note, Martha heads to Kurt’s table, but is shamed by the laughter of her classmates. Veronica is not entertained by her friends’ cruelty, and sees a handsome new student named Jason “J. D.” Dean roll his eyes. Sensing their mutual distaste, Veronica introduces herself, but Kurt Kelly and his sidekick, Ram, are threatened by Veronica’s action, and bully their new classmate. In response, J. D. draws a gun and shoots the boys with blank bullets. That evening, Veronica runs into J. D. at a convenience store and learns that he has attended many schools. As they part ways, Veronica grudgingly accompanies Heather Number One to a Remington University party, but becomes enraged by her friend’s narcissism, and accidentally vomits on Heather’s shoes. When Heather vows to ruin her reputation, Veronica returns home to write in her journal and pledges to end the girl’s tyranny. Just then, J. D. unexpectedly appears at her bedroom window and they make love outside. The next morning, the young lovers sneak into Heather “Number One’s” house and search for a liquid concoction that will induce vomiting. While Veronica mixes milk and orange juice, J. D. fills a mug with toxic “Hull Clean,” then distracts her with a kiss so she will mistakenly grab the wrong cup. When the couple awakens Heather, she righteously complies when J. D. dares her to drink the “hangover” antidote then falls over, dead. Concerned about the repercussions, J. D. notices Heather’s CliffsNotes copy of Sylvia Plath’s The Bell Jar and suggests they compose a confessional note in Heather’s handwriting, making the incident appear to be a suicide. The night of Heather Number One’s funeral, Veronica warily goes on a double date with Heather McNamara and the two football lettermen, Kurt and Ram. As Heather and Ram awkwardly make love in a cow pasture, Kurt chases Veronica but falls over, drunk. Suddenly, J. D. appears and disparages their school. The next day, Kurt initiates a rumor that Veronica performed oral sex on him and Ram. With J. D.’s encouragement, Veronica telephones Kurt, asking him to meet her at dawn with Ram, so she can act out their sexual fantasy. The couple plans to frighten the boys with J. D.’s guns, but Veronica is startled to discover J. D. loading real bullets. However, he assures her they are harmless tranquilizers and plans to make the shooting look like a double suicide. Copying Kurt’s handwriting yet again, Veronica writes a confessional, declaring that the boys were ashamed of their homosexual affair. The next morning, the lettermen meet Veronica and she orders them to undress. Just then, J. D. shoots Ram and chases Kurt through the woods until Veronica fires a bullet into his chest. Soon after, two police officers arrive at the scene, but Veronica and J. D. get away by pretending to be lovers making out in a car. Back at school, Veronica is outraged by J. D.’s sadism, but later acknowledges in her journal that the sham “suicides” ultimately transformed the victims into sensitive and heroic martyrs. Later, J. D. reveals that his mother committed suicide, and when he fires his gun at a radio playing the song “Teenage Suicide Don’t Do It,” Veronica ends their romance. In an effort to regain Veronica’s affection, J. D. blackmails Heather Duke with photographs of herself and her former best friend, the unpopular, obese Martha “Dumptruck” Dunnstock. He encourages Heather Duke to become the new Heather “Number One” with the hope of provoking Veronica’s murderous rage. He later burns the photographs and asks Heather to promote a petition endorsing the prom band, Big Fun, with their hit, “Teenage Suicide Don’t Do It.” Meanwhile, Veronica renews her friendship with nerdy Betty Finn and complains to her parents about the media’s exploitation of the “suicides.” Just then, Heather Duke arrives to announce that Martha “Dumptruck” attempted suicide, and Veronica slaps her face. However, the two girls reconcile and laze in Veronica’s bedroom, listening to a confessional radio show. When Heather McNamara anonymously phones in to admit guilty feelings about her boyfriend’s suicide, Heather “new Number One” Duke vows to make her fellow Heather the laughing stock of Westerburg High. The next day, the grieving Heather McNamara runs to the bathroom during class, and Veronica follows to prevent the girl from overdosing on pills. After school, Veronica discovers that J. D. told her parents she was suicidal, and they apprehensively hand her a letter from him. Composed in her own writing style, the note reads, “Recognize the handwriting?” Veronica is terrified by J. D.’s suggestion that he could kill her, too, using the “suicide” alibi. That evening, Veronica awakens from a nightmare in which J. D. murders the new Heather Number One and she vows to end his killing spree. Later, J. D. breaks into Veronica’s bedroom and finds her hanging from the rafters in an apparent suicide. Admitting his intention to kill her, J. D. declares his love and confesses that the Big Fun petition, unwittingly backed by Heather and signed by the entire student body, was really a declaration of mass suicide. J. D. reads aloud, stating that the undersigned have agreed to blow themselves up at Westerburg High to protest the exploitation of teen angst. The next day, J. D. arrives at school with a bag full of explosives and sets them up in the gymnasium, knowing the students will soon convene there for pep rally. Meanwhile, after feigning suicide, Veronica returns to school and finds J. D. in the boiler room beneath the gymnasium. When she holds her former lover at gunpoint, he knocks her unconscious, but she comes to with just over two minutes remaining on J. D.’s time bomb. He kisses her, but she knees him in the groin, regains possession of the gun, and shoots him in the hand. She orders J. D. to reveal a method of disabling the bomb, but he complains of being unloved, and argues that the only place for social equality is in heaven. With four seconds remaining on the time bomb, Veronica shoots J. D. as he shoves a knife into the bomb, disabling it. Assuming her lover is dead, Veronica stumbles outside, but J. D. follows and reveals a ticking time bomb beneath his trench coat. Meanwhile, students at the pep rally are oblivious until they hear an explosion outside. With J. D. now dead, Veronica returns inside to declare her successful overthrow of Heather Duke’s reign. Taking on the role of social trendsetter, Veronica suggests that she and Martha “Dumptruck” ditch the prom together.