Plot
At Westerburg High School in Sherwood, Ohio, Veronica Sawyer is part of a popular-but-feared clique that includes three wealthy and beautiful girls with the same first name: Heather Duke, Heather McNamara, and the ruthless queen bee, Heather Chandler. Tired of the clique abusing its power, Veronica longs for her old life with her kinder but less popular friends. She becomes fascinated with new student Jason "J.D." Dean after he pulls out a gun and fires blanks to scare football-player bullies, Kurt and Ram. Outsider J.D., whose mother committed suicide, has a strained relationship with his explosives-obsessed demolition mogul father.
Veronica goes with Chandler to a frat party at Remington University, where she refuses to have sex with one member, unlike Chandler, who is coerced into performing oral sex. When Veronica drunkenly vomits on Chandler, Chandler vows to destroy Veronica's reputation in retaliation. Later, J.D. breaks into Veronica's house through her bedroom window, and they have sex. They express to each other their mutual hatred of Chandler's tyranny.
The next morning, Veronica and J.D. break into Chandler's house, planning revenge by using a fake hangover cure to make Chandler vomit. Veronica mixes orange juice and milk into a mug, but J.D. pours a mug full of drain cleaner, which Veronica accidentally grabs, mistakenly killing her. Veronica is horrified by the accident, but J.D. urges her to forge a dramatic suicide note in Chandler's handwriting. The community regards Chandler's apparent suicide as a tragic decision made by a troubled teenager, making her even more worshipped in death than in life. Duke uses the attention surrounding Chandler's death to gain popularity by going to many different news stations, feeling the need to be the clique's new leader.
McNamara later convinces Veronica to go with her, Kurt, and Ram on a double date. J.D. finds the four teens that evening in a field, and Veronica leaves with him as Kurt passes out, while Ram rapes McNamara. The boys spread a false rumor about Veronica performing oral sex on them, ruining her reputation. J.D. proposes that he and Veronica lure the boys into the woods, shoot them with tranquilizers, and humiliate them by staging the scene to look like they were lovers participating in a suicide pact. In the forest, J.D. shoots Ram, but Veronica's shot misses Kurt, who runs away. J.D. chases Kurt back toward Veronica, who, realizing that the bullets are in fact lethal, fatally shoots him in a panic. At their funeral, the boys are made into martyrs to homophobia. Horrified that J.D. is murdering students he dislikes, Veronica breaks up with him.
J.D. blackmails Duke into getting every student to sign a petition that, unbeknownst to her, is intended to act as a mass suicide note. Martha, an overweight and oft-bullied girl, attempts to kill herself by walking into traffic. She survives but is badly injured and mocked by her peers who believe she was attempting to copy the popular kids. McNamara calls a radio show to discuss her depression. Duke tells the entire school about the radio call, leading to McNamara being bullied. McNamara attempts suicide by overdosing in the girls' bathroom, but Veronica intervenes.
Veronica returns home, where her parents inform her that J.D. stopped by, proclaiming that he is worried she will attempt suicide. Realizing that J.D. plans to kill her, she fakes her own suicide by hanging. J.D. finds her and, assuming she is dead, gives a monologue revealing his plan to blow up the school pep rally and frame it as a suicide pact.
J.D. plants dynamite in the gymnasium equipped with remote detonators. He proceeds to the school's boiler room to place dynamite with a countdown detonator. Veronica confronts J.D. in the boiler room and shoots him, resulting in him accidentally cutting the wires to the detonator with his switchblade. Veronica goes outside, and J.D. follows her with a bomb strapped to his chest. He offers a personal eulogy and detonates the bomb, killing himself. As students and faculty rush to see what happened, Veronica walks back inside, disheveled and covered in soot from the explosion. She confronts and condemns Duke, then invites Martha to spend prom night watching movies together.
