Three years after escaping an abusive relationship, Suyeon retreats to her father's rural mansion to rebuild her life, writing horror fiction by day. When her caring boyfriend Shinji arrives for the holidays, a strange cut from a rusted razor sets something in motion. Something that wears his face but isn't him anymore. Isolated, with nowhere to run, they can no longer tell nightmare from reality as something begins to hunt them down.

Park Jung-gu sends out homemade bombs to people he finds online who are likely to use them, yet these devices are unused. One day, Jung-gu meets Lee Hyo-min, a delinquent student at his university and sends him a package. Soon an explosion in a delivery truck hits the news. Before long, Hyo-min discovers who is sending him the packages and the two form a tenuous relationship. However, Hyo-min's unpredictable behavior becomes dangerous and Jung-gu finds himself caught in a situation that he can no longer handle.