One day, Sung-soo receives a phone call that his estranged brother is missing and goes to his brother's apartment for the first time in decades to look for him. There, he finds strange symbols carved into every door and meets his brother's neighbor Joo-hee and her young daughter Pyeong-Hwa. When Sung-Soo tells her he went to visit his brother, she suddenly become hostile and kicks them out of her room. Sung-Soo decides to stay in his brother's room.
