Ronald Reagan High School's power clique consists of Courtney Shane (Rose McGowan), Julie Freeman (Rebecca Gayheart), Marcie Fox (Julie Benz), and Liz Purr (Charlotte Roldan). They control the school through beauty, sex, and intimidation. Of the four, only Liz is actually decent and liked by normal kids, and able to keep hateful Courtney in check. Unfortunately for Liz, she's also the only thing keeping Courtney from becoming prom queen. To achieve her goal, Courtney convinces Marcie and Julie to kidnap Liz on her 17th birthday and force her to eat until she's too fat to win. The three sneak into Liz's house, tie her up, stick a jawbreaker in her mouth, and gag her to keep her quiet before they throw her into the trunk of a car.

When they decide to free her, though, they find Liz has choked to death. Courtney decides not to go to the police; her brilliant idea is to take the body back home and create a death scene where Liz is strangled during kinky sex. Predictably, the girls screw it up, and they end up with a witness, social outcast Fern Mayo (Judy Greer). To buy her silence, Courtney draws her into the clique, transforming much more than just her outward appearance. The identity of Fern disappears, to be replaced by the very popular Vylette. In parallel to the rise of Vylette, we witness Julie's descent. Overcome with guilt over Liz's death, Julie drops out of the clique, and without the veil of protection from the others, she is now a target of abuse throughout the school. Courtney's ordeal has just begun as Vylette now challenges her for prom queen and Julie, with the help of another outcast, Zach (Chad Christ), now wants to reveal the truth behind Liz's death.