Danielle, Tiffany, and Brooke are the three richest, most popular girls in their high school, nicknamed The Huns because of their exclusive Hundred Pines estate. Danielle and Tiffany are cruel and spiteful, whereas Brooke is kind but easily intimidated and manipulated by Danielle and Tiffany. A lone ex-jock, Drew, mourns the death of his girlfriend Charity Chase, and despite Danielle’s charm, he cannot be drawn to her. Charity’s fate is darkly tangled with theirs: although Charity was believed to have committed suicide, it isn’t so. Danielle, Tiffany, and Brooke lure Charity to a cliff, intending to terrify her into breaking up with Drew, but their plan ends in Charity’s death by accident.
A year to the day of Charity’s death, Romanian exchange student Katarina arrives during class with the clumsy Media Arts Professor, Mr. Chauncey. Katarina and Drew quickly become friends, and Danielle’s jealousy flares as she watches their bond develop. In an attempt to grow closer to Drew, Danielle takes a job at the elderly home where he also works. There, she is assigned to care for an old lady she believes is catatonic. Seizing the moment, Danielle, Tiffany, and Brooke raid the old lady’s cupboard and eat her box of chocolates, a small act that foreshadows the strange turn their lives will take.
Over the next two weeks, the three begin to notice strange changes: back pains and hair turning gray, signs that they are aging at a rapid speed. They worry that Katarina—whom they now suspect is Charity’s ghost come back to seek revenge—may be behind it. Desperate to regain their youth, they convince themselves that the only way to restore their lives is to kill Drew so his spirit can be with Charity. At Danielle’s eighteenth birthday party, they lure Drew to the gorge where Charity died. Katarina steps in and clarifies she is not Charity’s ghost, but Danielle, driven by fear and vanity, still contemplates shooting them both. Brooke, finally recognizing how far they’ve gone, tries to stop Danielle from pulling the trigger, and Drew disarms her. A party guest dressed in a clown suit—secretly connected to the party’s host—causes a distraction, and Danielle ends up shooting instead. Exhaustion and fear overtake Tiffany and Danielle as the plan unravels.
Now in the old age home, Tiffany remains hooked up to life support while Danielle is barely alive. Mrs. Witt, Charity’s grandmother, reveals that she overheard Danielle bragging about Charity’s murder. Witt explains she poisoned the chocolate box with an aging chemical, a scheme developed with help from the late roommate’s husband who worked in biological warfare technology. Brooke survives, having shown restraint, while Tiffany dies during Witt’s revelation. Danielle dies soon after, flipping a defiant bird toward Witt as she passes.
At their funerals, Drew and Katarina attend alongside Brooke, who has undergone plastic surgery to improve her appearance but still looks far older than she should. Chauncey forgives Brooke, recognizing she wasn’t as cruel as Danielle and Tiffany. The pair are later seen in a luxurious room, seemingly restored to youth and happiness, but the scene reveals a grim truth: they are in hell, forced to endure the company of their school’s most annoying—Jonathan Wharton, the dork whose devotion to Danielle knows no bounds. Wharton, revealed to have taken his own life to be with Danielle forever, briefly morphs into the devil, leaving Danielle and Tiffany to confront the consequences of their actions and the haunting realization of who they have become.
