A Tale of Two Sisters

A teenage girl, Su-mi, is being treated for shock and psychosis in a mental institution. She is eventually released and returns home to her family's secluded country estate with her father Moo-hyeon and younger sister Su-yeon. The sisters' stepmother, Eun-joo, constantly requires medication. Su-mi and Eun-joo verbally clash multiple times. Moo-hyeon is uninterested in Su-mi's complaints and rejects her request to remove a wardrobe in Su-yeon's room, as it seems to upset Su-yeon. One night, Su-yeon has a nightmare of her late mother's ghost and flees into Su-mi's room for comfort. Afterwards, Su-mi also has a nightmare with a ghost while Su-yeon sleeps next to her. The next day, Su-mi finds family photos which reveal that Eun-joo was formerly an in-home nurse for her then-terminally ill mother. She discovers bruises on Su-yeon's arms and suspects Eun-joo to be responsible. Su-yeon neither confirms nor denies this. Instead, she begins sobbing and runs away when Su-mi gets angry about her silence. Su-mi confronts Eun-joo about the bruises, but Eun-joo refuses to apologize, explaining that they were "retribution." That night, the sisters' uncle, Sun-kyu, and aunt, Mi-hee, arrive for dinner, and Eun-joo tells bewildering stories involving Sun-kyu, which he denies remembering. Mi-hee suffers a violent seizure and almost suffocates. After recovering on their way home, Mi-hee tells Sun-kyu that she saw "a girl" beneath the kitchen sink during her seizure. Eun-joo searches the kitchen when the cupboard below the sink opens by itself. She sees a hair clip on the ground, but the ghost girl violently grabs her arm when she tries to pick it up. Eun-joo later finds her pet birds killed and her personal photos defaced. She believes that either one or both of her stepdaughters are responsible and locks Su-yeon in the wardrobe. Su-mi releases her and tells Moo-hyeon, who had just found and buried another dead bird, about Eun-joo's abuse. Moo-hyeon begs her to stop acting out and exasperatedly reveals that Su-yeon is dead. Su-mi refuses to believe it as she is sure that her sister is right next to her, sobbing uncontrollably. The next morning, Eun-joo drags a bloodied sack through the house, whipping it in anger. Su-mi believes that Su-yeon is inside the sack. Eun-joo and Su-mi get into a physical altercation. Moo-hyeon arrives to find an unconscious Su-mi. It is ultimately revealed that Su-mi and her father were alone in the house all along. Su-mi is suffering from dissociative identity disorder and has two personalities: herself, and a ruder, more distant variation of her stepmother Eun-joo. The "body" in the sack that Su-mi was whipping was actually porcelain dolls, and she was also the one who killed the birds. Su-yeon is also revealed to be long dead, her presence having been a hallucination by Su-Mi. Moo-hyeon and the real Eun-joo, a much different woman than what Su-mi had envisioned, send Su-mi back to the mental institution.