Hyun Jin prepares for her exam to become a public official. She moves into an old apartment with neighbors who seem suspicious. Hyun Jin begins to tutor high school student Joo Hee. She lives next door to Hyun Jin. Hyun Jin then hears a secret story about Joo Hee's family and feels sorry for her. Joo Hee tells her that she wants to kill her neighbors. A few days later, the neighbors are murdered and Hyun Jin suspects Joo Hee as the suspect. Meanwhile, Public Official Park heads to the old apartment building after hearing of the murder case. She thinks about a kid she forgot about for years.