University professor Li Ming and his family have been subjected to long-term harassment by their neighbor, Chen Haisheng. What begins with noise and prying eyes escalates into threats of breaking into their home. During his investigation, Li Ming discovers that Chen Haisheng is connected to an old case: five years ago, a family living in the same apartment building mysteriously fell to their deaths, and Chen Haisheng was the witness at the time. As the truth draws closer, Li Ming realizes that his family has been targeted for a reason.