The film tracks protagonist Chen Zhihui who succumbs to trauma and frustration when he is released after spending 20 years in prison and becomes a serial killer.

A woman living alone starts to feel uneasy when she discovers traces of a stranger having been in her home. Single and beautiful Fang Hui works alone in the big city. One night, she suddenly hears someone outside the door trying to break in, violently pulling the door. A security guard notices that the floors monitor are broken. This made Fang Hui's peaceful life of living alone suddenly shrouded in the shadow of anxiety. When the night came again, sleeping Fang Hui vaguely notices that someone had entered her room... but she didn't find any signs when she wakes up.