Felix’s Halloween-night quiet life collides with a web of secrets, violence, and family duty when a long-festering grudge bursts into the open. At a tense end-of-term party, a shy outsider named Felix quietly observers a group of friends—among them the brash Chris, his more reserved girlfriend Gemma, Paul and his sharp, abrasive partner Eleanor, and Paul’s conflict-prone circle. The party hums with thinly veiled tensions: Felix quietly admires Gemma, Luke pressures Felix with drugs, and Gemma politely declines Felix’s invitation to connect. The mood shifts from flirtation to danger as a drunken upstairs encounter between Paul and Eleanor dissolves into a game of truth or dare that unsettles everyone. When Felix chooses Gemma as the object of his fantasy, jealousy erupts and Chris lashes out, culminating in a brutal public confrontation. Gemma, feeling betrayed, steps in to console Felix, setting the stage for a haunting afterglow from that night.
Months pass, and a sparkling winter invitation drops into the five friends’ lives for Felix’s surprise birthday. They arrive at a manor that exudes wealth and remoteness, hinting at a lineage of luxury and secrecy. The address proves a decoy, and a groundsman named Woodbridge guides them to a remote shack hidden in the forest, where the enigmatic Felix’s elder brother Justin awaits. Justin, a battle-hardened veteran recently returned from three tours, exudes charm with a chilling edge—an edge sharpened by a casual but brutal intolerance toward those he deems unworthy or “different.” He claims a last-minute cancellation kept Felix from joining the party, then reveals a more ominous truth: Felix never left the party at all; he died by suicide in the shack, his death sealed with a postcard reading “Truth or Dare, bitch!” and a whispered insistence that someone among them is responsible.
What follows is a descent into coercion and fear. When the guests attempt to depart, Justin shoots Paul in the leg and enlists Luke as an unwilling accomplice in a night of control. The group is restrained as Justin reengineers the party game into a macabre ritual called “The Acid Test.” Gemma is fed a tube connected to two glass jars, one allegedly containing water and the other battery acid. Chris, forced to participate, is presented with two jars and, through a manipulative switch of roles by Justin, ends up ingesting acid and dying in a torrent of blood. The room fills with panic, and an intruder’s arrival—Jonesy, a drug-dealing associate of Luke—forces Justin to escalate. A staged choice involving a 50-50 gun leads Luke to shoot Jonesy, and Gemma seizes the chance to escape through a back window.
Back at the mansion, Gemma discovers Felix alive but severely disabled, cared for by Woodbridge who reveals that he found Felix hanging in the shack and has tended to him ever since. A confrontation erupts between Gemma and Woodbridge, ending with Woodbridge fatally wounded as Justin storms in, brutalizing Gemma’s efforts to help and killing him in a cold, calculated moment.
Meanwhile, Luke’s grip on the situation begins to crack. He admits to having sent the postcard himself, hoping to maintain Justin’s protection and his own safety, while Eleanor plays a dangerous game of leverage. She orchestrates a retreat from the shack, but not before she helps free Paul and Eleanor, who had been bound. Luke’s fear of punishment collides with Eleanor’s ruthless pragmatism as she orchestrates a violent escape route, but not before Luke is fatally compromised—Eleanor’s counterattack involves biting off Luke’s finger, sending him reeling and causing him to impale himself on a nearby tool.
With Paul, Eleanor, and Gemma finally free, they race toward escape, but the night’s toll has already rewritten their fates. Justin returns to the scene with Felix, who is now in a wheelchair, and a brutal brawl erupts. Eleanor manages to shoot Justin in the shoulder and douses him with acid, turning the confrontation into a brutal struggle for survival. Justin binds Gemma to a post, and Paul attempts to start a car to aid their escape. In a devastating twist, Eleanor reveals that the postcard was not the true lever behind Felix’s tragedy: a hidden video blackmailed Felix into submission, exposing a sexual act Felix had been forced to perform on the unconscious Paul. The fear of this humiliation and exposure drove Felix to attempt suicide, a burden Eleanor exploited for her own gain.
Armed with this revelation, Eleanor flee-sells the house into chaos. She abandons Paul, hands him a grenade, and escapes as the mansion erupts in a violent inferno. The explosion swallows the brothers and their torment, leaving the remaining survivors to reckon with the night’s brutal cost and the heavy truth behind Felix’s death.
The film closes on a note of bleak consequence, where loyalty frays, trust fractures, and the secrets of a privileged family—and the consequences of hidden desires—come roaring to the surface, leaving a trail of broken lives and a house that burns as a testament to the evening’s violence.
