Door Lock is a 2018 South Korean psychological horror-thriller film
directed by Lee Kwon, starring Gong Hyo-jin, Kim Ye-won, and Kim Sung-oh. The film was released on December 5, 2018.
Kyung-min, portrayed by Gong Hyo-jin, lives alone in a studio apartment in Seoul and works as a bank clerk. Her seemingly normal life is disrupted by unsettling incidents. She discovers traces of a stranger breaking into her apartment. The cover of her highly secured door lock is left open, and she finds a cigarette butt in front of her door. She changes her password after feeling uneasy. One night, she hears someone attempting to unlock her door.
When Kyung-min calls the police, they dismiss her concerns. As more unsettling events occur, including a murder in her apartment complex, Kyung-min realizes she cannot rely on the police and begins her own investigation with the help of her friend, Hyo-joo. She finds a code card in her apartment that leads her to another apartment in her building, bringing her closer to the murderer than she intended.
The film explores the vulnerability of women in South Korean society and the terror of feeling unsafe in one's own home.