A lonely meter maid named Christopher stumbles upon a Halloween invite to a party called “Murder Party,” and, dressed in a cardboard knight costume, he travels to Brooklyn hoping for a night of eccentric fun. What begins as a misguided attempt at social connection spirals into a deadly trap orchestrated by a cadre of deranged art students who have turned their gathering into a grotesque performance piece. The group arrives in costume—Paul, a gothic vampire, Macon, a menacing werewolf, Sky, a zombie cheerleader, Lexi, a nod to Pris from Blade Runner, and Bill, a Baseball Fury from The Warriors—and they intend to murder their guest as an act of art to win the approval (and a sizable grant) of their wealthy patron, Alexander.
The already tense atmosphere sours when Sky, who starts nibbling on Christopher’s pumpkin raisin bread, reveals she is allergic to non-organic raisins. She collapses, hits her head, and dies. The group, embarrassed and terrified, hides the body as the night’s plan teeters on the edge of collapse. Alexander arrives with a friend named Zycho (who is unknown to the party) and his dog Hellhammer, a creature claimed to be part dingo. Alexander also reveals Zycho as his drug dealer, complicating the dynamics and raising the stakes.
Each member weighs how they will carry out the murder in this perverse art project, and the party soon leans on alcohol and drugs to loosen inhibitions. They resolve to wait for the witching hour to strike as one, stabbing Christopher together. Macon steps out to fetch pizza, while Alexander indulges in sexual escapades with Lexi and Paul, triggering jealousy and a deeper rift when he returns to find them together. The tension escalates as Macon, intoxicated and reckless, pours alcohol on himself and catches fire—an accident only Christopher seems to notice amidst the chaos. Paul, obsessed with photography, begins documenting the night but laments the lack of help from others.
As boredom gnaws, they turn to truth-or-dare, aided by Sodium Pentothal, and the group divulges secrets that reveal fragile egos and hidden resentments. One by one, they ingest the same needle’s worth of truth, save for Alexander, who injects his dose into a slice of pizza. The confessions illuminate fractures within the group and the hollow nature of the grant-driven art world. Bill, who mostly keeps to himself, discovers he is the target of mockery and fear that he may be kicked out simply because his work is too good for the others. Macon confesses a long-standing love for Lexi and recounts a high-school moment—sharing a popsicle on a water tower—that he still clings to as a memento, only to be rebuffed by her. Alexander tries to secure the last laughs by sending Zycho to fetch more crank.
The night spirals further when Paul calls in a professional assistant to aid with his photographs; the assistant, unaware of the murder party, inflames tensions and leads to a confrontation. Alexander is injected with truth serum, the group again pressing him for the promised grant, and they discover that Alexander is a fraud: a fry cook pretending to be a patron who intends to murder the participants, steal their work, and sell it as valuable art. Lexi and the assistant intervene to put out Macon’s blaze, but Zycho returns with crank, and Alexander orders him to kill everyone. Paul is shot in the head, seemingly unconcerned by the interruption, followed by the assistant’s death and Zycho’s assault on Lexi. Macon, still alive and disfigured, wields a chainsaw in a desperate bid to survive, killing Zycho and collapsing soon after.
Lexi rushes to free Christopher, but Bill, now completely unhinged, murders Lexi with an axe and is then consumed by the chaos as Hellhammer goes after the crank and turns on Alexander. Bill finishes off the wounded patron with a bat and hunts the last survivor, Christopher, who has escaped. Macon, burning but alive, confronts Bill with the chained saw, using it to defend himself. The chase leads to an art student party, where Chris hides inside a performance-art exhibit while Bill searches for Alexander, who promised him a grant but never delivered. Bill storms the exhibit, killing the artists inside and cornering Chris.
A dramatic moment unfolds when Macon arrives at the party, trying to plug in the chainsaw, but trips and falls from a balcony. The powered blade hangs outside a window, and Chris seizes the opportunity, grabbing the saw and using it to sever Bill’s head in self-defense. He then topples Bill with a pumpkin smash, shouting the famous line, “I JUST WANTED TO PARTY!” as he escapes the chaos and dials emergency services on a security guard’s phone. The partygoers, convinced the carnage is part of an art installation, interpret the scene as a performance rather than a crime.
Back home, Christopher disposes of his anti-anxiety meds and returns to a quiet domestic moment: his cat, Sir Lancelot, has reclaimed his chair, and he sits in his blood-spattered knight costume, turning on the TV and processing the night’s events in exhausted, almost ceremonial calm. The film lingers on the unsettling blur between art and murder, leaving Christopher to confront the harsh truth of what he survived and the uneasy sense that, in this world, some performances are all too real.
