Flashbacks reveal the day that led Su-mi to be institutionalized. Whilst her terminally ill mother was still alive, her father engaged in an adulterous affair with Eun-joo, whilst she was still an in-home nurse. This upsets the sisters and drives their mother to hang herself in the closet of Su-yeon's bedroom. Su-yeon attempts to revive her but the closet collapses on top of her, slowly crushing her to death. Eun-joo walks in and considers saving Su-yeon, but she encounters Su-mi, who engages in a heated confrontation with her. Angry at Su-mi's insults, Eun-joo decides to leave Su-yeon to die and tells Su-mi that she'll "regret this moment." Su-mi leaves the house, unaware of both her sister and her mother's fates.