Bill Whitney, Billy Warlock lives with his parents and sister in a sprawling Beverly Hills mansion, navigating the glossy trap of a life built on wealth. He confides in his therapist, Dr. Cleveland, Ben Slack, that he does not trust the world his family inhabits. The uneasy peace is jolted when his sister's ex-boyfriend, David Blanchard, Tim Bartell, slips him a secretly recorded tape that seems to show the family taking part in a murderous orgy. Bill’s doubt tightens into fear as he replays the recording, only to hear it change into footage of his sister’s debutante party. When he tries to meet David to secure another copy, he discovers a grim scene: an ambulance and police surround a crashed van, a body is loaded into the back, and the face remains hidden from him.
Bill attends a party hosted by his affluent classmate Ted Ferguson, where the grown-up truth behind the tape is confirmed. He leaves the party in a hurry with Clarissa Carlyn, Devin DeVasquez, a stunning girl he has long admired. The next day, Bill confronts his parents and Jenny Whitney, his sister. At David Blanchard’s funeral, Milo, played by Evan Richards, uncovers a troubling hint that David’s corpse might not be what it seems. Then Bill is contacted by Martin, his rival for the high school presidency, and at their arranged meeting, he discovers Martin with his throat slashed. When the police return, Martin’s body is gone, and the next day Martin reappears at school, very much alive, adding to the sense that something deeply distorted lurks beneath the surface of Bill’s world.
Back at home, the pressure intensifies as Bill’s family drugs him with the aid of Dr. Cleveland. Milo trails him as he’s taken to a hospital, where he awakes and pulls a curtain aside, thinking he hears David crying out, only to find nothing there. Milo and Clarissa try to warn him, but he drives back to the house, where the night’s grotesque spectacle unfolds.
Inside the mansion, a large formal party roars to life. Dr. Cleveland reveals a chilling truth: Bill’s family and their circle are a different species from him, a realization born from being adopted into their bloodline. To prove their claim, they summon David as a still-living human sacrifice. The guests shed their clothes and begin shunting, a brutal process in which their bodies deform and meld into an almost formless mass. As they feed on the nutrients from David’s body, they absorb him and prepare to do the same to Bill, who is swiftly pursued by the grotesque crowd.
In the chaos, Bill is forced into a brutal clash with Ted, who attacks him as the others surge in their eerie unity. Bill manages to kill Ted by reaching inside his body mid-shunt and pulling his body inside out. He escapes with Milo and Clarissa, who has betrayed the others after falling in love with him. The trio bursts from the house, sprinting away as the party’s horrific ritual continues behind them.
