In the scorching summer of 1988, three friends—Alexis Butler, Val, and Bev—set off for a heavy metal concert in Indiana. Their carefree adventure takes a bizarre twist when a milkshake is flung from a mysterious blue van, splattering their windshield. Upon arriving at the concert, they encounter an unsettling sense of déjà vu as the same van reappears, its occupants eager for interaction. Val, always the thrill-seeker, decides to escalate the night’s tension by igniting a firecracker, thus coaxing three boys—Ivan, Kovacs, and Mark—from their vehicle, who is on his way to Los Angeles.
As the night unfolds, Alexis invites the group back to her father's vacant mansion, where the ambiance takes a dark turn. While Bev and Mark appear to be connecting, a sense of tension lingers as Bev purposefully keeps her distance from him. The evening spirals into madness as the girls devise a lethal game of Never Have I Ever, spiking their guests' drinks in a deadly plot to claim them.
The sinister organization known as the Daughters of the Dawn, with which Alexis is entangled, has already claimed eighteen lives in horrific manners. As night progresses, Ivan criticizes Alexis’s extremist religious views, leading her to a violent explosion of rage where she fatally stabs him.
Meanwhile, Mark and Kovacs attempt to evade their would-be assassins, finding refuge in a pantry as they plot their escape. Their short-lived safety is shattered when Susan, Alexis's soon-to-be ex-stepmother, comes home to witness the bloody horror unfolding. In a chilling event, she discovers Ivan's corpse, only to meet her grisly fate at Alexis's hands.
As the chaos escalates, police begin to converge on the scene, and Alexis makes a frantic getaway, pursued by an officer keen on uncovering the truth. Seizing the moment, Val takes down her pursuer, seizing his weapon and ending his life in a brutal act.
As the dust begins to settle, Bev steps in, wielding an electric outboard trolling motor as a warning to her companions. The usually loyal pair of Alexis and Val find themselves at odds over what to do next, but it's clear both are determined to complete their twisted plan to the bitter end. As Bev confronts a moral crossroads, she realizes that she cannot condone the murder of innocent men. In a dramatic standoff, she forces her friends to reconsider their actions, ultimately deciding to release Mark and Kovacs.
As Kovacs’s condition deteriorates, Bev races to keep him alive and secure a way to a hospital. Mark embarks on a desperate search for car keys, eventually obtaining them from Alexis, but not without a fierce confrontation that leaves both injured. The turmoil reaches new heights when Val directs her aggression toward Bev, launching a savage attack that ends only when Bev retaliates by igniting Val’s hairspray-soaked hair, setting her ablaze.
Amidst the chaos, Kovacs catches sight of John Henry Butler, Alexis’s father and the Daughters of the Dawn pastor, and rushes outside to confront him. This encounter leads to Kovacs being shot, sending him crashing back into the house, where Bev finds him barely clinging to life as he pleads for her to save Mark.
The struggle continues, and John Henry turns his fury on Mark, shooting him and then chastising Alexis for her failures. He insists that sacrifices must be made to escape the peril she created, even attempting to strangle her. However, Bev intervenes, striking John Henry down. A deranged Alexis then confronts Bev in a fierce fight but ultimately succumbs to her own recklessness, plunging out a window, leaving a surviving Mark to flee with Bev.
As they escape together, their path is abruptly interrupted by a relentless Alexis, who meets her end in a gruesome reckoning at Bev's hands. In the aftermath, John Henry feigns injury, crafting a deceptive tale of his daughter succumbing to dark temptations and joining a satanic cult. With their troubles concealed behind them, Bev and Mark embark on an uncertain journey into the unknown, forever changed by the night's horrific events.
