A regular girl, Veronica, tries to survive the social jungle of high school by sticking with the three most popular girls at school who are all called Heather. As she meets a sociopath named JD, her life spirals into a continuous cycle of hate, unintentional murder and indifference, as she exacts revenge on her enemies, also known as her best friends.
Veronica mingles with Heather I, II and III to be as popular as them, even though she hates them. She hates them enough to wish they were dead, though she would never want to be their cause of death. When she starts dating Jason Dean, however, she finds herself involved in the murders of most of her enemies, covered up as suicides.
Three high school girls named Heather run an iron clad social clique at high school. One of their anointees, Veronica, isn't sure she wants to fit into the clique, particularly when she has to snub some of her old friends at the Heathers' behest. When Veronica meets the new guy at school, she starts pulling away from the clique, while some of the more popular students start showing up dead with suicide notes.
Dear Diary: Veronica Sawyer is sick of being part of the Heathers, the most powerful clic of Westerberg High; making fun of Martha Dunnstock ("Dumptruck"), the fat girl, or doing some stupid polls is something she'll never get used to. Meanwhile she meets JD, a cool rebel guy who wouldn't mind shooting a gun at school just to make his point. Remington University's party is where Veronica has to go as a Heather, and there's where she gets her ultimatum as a Heather from Heather Chandler, the head of the Heathers. So Veronica and her lover JD "accidentally" kill Heather Chandler and manage to cover it up by making a suicide note. Will this be just the beginning of the assasination-turned-suicide serie of Westerberg High which nor the FBI, the CIA or the PTA would be able to stop? Or will Veronica be able to pull herself together and stop her psychotic lover from killing absolutely EVERYONE at school?
In order to get out of the snobby clique that is destroying her good-girl reputation, an intelligent teen teams up with a dark sociopath in a plot to kill the cool kids.
- Veronica is part of the most popular clique at school, made up of Heather Duke, Heather McNamara and led by Heather Chandler. Tired of the way Heather Chandler bullies and controls everyone Veronica wishes she was dead so that she could free to do as she wants instead of what Heather Chandler wants.
Veronica then meets J.D, a dark rebel, who says they should teach Heather Chandler a lesson by making her drink drain cleaner. Heather Chandler does and dies from chemical poisoning instantly. To cover up the murder J.D tells Veronica to write suicide note in Heather Chandler's handwriting.
The cruelty and bullying doesn't stop however, as Heather Duke merely replaces Heather Chandler as leader, and her suicide is seen as glamorous and cool. J.D then tricks Veronica into shooting two of the football players, Kurt and Ram, who were harassing her, and covering it up with another suicide note that says they were secretly gay.
Veronica becomes scared of J.D realises that he intended to kill them while she just wanted to scare them. His next plan is to kill Heather Duke, but Veronica wants no part of it, so instead he plans to blow up the school, after everyone has sign a "petition" which is actually a group suicide note.
Veronica shoots J.D forcing him to leave the bomb in the school and go outside where he then straps the bomb to himself. Veronica watches as he blows himself up, and then returns inside to confront Heather Duke. She tells Heather Duke "there's a new sheriff in town" and walks off talks to the school nerd, suggesting that she will now be leader of the school.