In the wake of a brutal mass murder at Ms. Park's residence, five people lie dead and two survive: [Ms. Park] and her caretaker, Mi-Ja. Mi-Ja recounts the harrowing night to Detective Ma, setting in motion a tense, truth-seeking investigation that peels back layers of fear, resentment, and buried secrets.
Mi-Ja takes care of her former teacher, [Ms. Park], and together they arrange a class reunion with Park's former students: [Se-Ho], [Eun-Young], [Dal-Bong], [Sun-Hee], [Myung-Ho], and [Jung-Won]. Each graduate carries a grudge against Park for different reasons: Se-Ho and Eun-Young felt belittled by her when they were poor; Dal-Bong bears the pain of a leg injury after a punishment that required endless squats; Sun-Hee recalls cruel jibes about her obesity; and Myung-Ho accuses Park of sexual abuse. The friendless, quiet [Jung-Won], who was once teased for defecating in class, stopped attending school after his mother was struck by a car. Still, the group tries to wear a facade of cheer for the reunion, masking the simmering rage beneath.
Tensions flare as the night unfolds. [Se-Ho] drunkenly erupts during the barbecue and is dragged to the basement by a bunny-masked figure, who kills him. [Eun-Young] lunges at [Ms. Park] in a bath, attempting to drown her, but fails; the same masked assailant then strikes and kills Eun-Young. [Dal-Bong] makes a doomed attempt to attack [Ms. Park], but is halted by the bunny figure, who inserts insects into his ears to end his life. Flashbacks reveal the group’s laughter at Park’s deformed son, who wore a bunny mask to hide his face; only [Jung-Won] wanted to befriend him. In a separate struggle, [Sun-Hee] tries to push [Ms. Park] off a cliff, but Mi-Ja intervenes; Sun-Hee falls to her death. [Mi-Ja] is knocked unconscious by [Myung-Ho], who would have set Park on fire if not for the bunny figure killing him. The killer is eventually revealed to be [Jung-Won].
Detective Ma’s inquiry leads him to Jung-Won’s supposed apartment, where he finds only his mother’s decaying corpse, women’s clothing, and articles about the supposed success of Park’s former students—contradicting Mi-Ja’s claims. It becomes clear there is no male student named “Jung-Won”; the name is, in fact, Mi-Ja’s real name. She engineered this entire tale to weaponize her own past: she was poor and overweight, broke her leg under Park’s punishment, and endured her mother’s confrontation with Park, a confrontation that left her mother disabled and eventually dead. Jung-Won then assumed Mi-Ja’s identity and stepped into the role of Park’s caretaker to orchestrate the killings at the reunion.
Driven by fury and despair, Jung-Won drives [Ms. Park] to the beach and vents before jumping from the pier, a suicide that leaves Park to watch in mute horror. The film closes with Park’s wheelchair sitting on the pier, a chilling implication that she may have chosen death as well.
