A high school student Do-yeon is the victim of bullying in school. He is not good at studying or at fighting. One day, an unexpected change happens to his body. On a pitch-black stormy night, a woman is visited by a stranger seeking shelter. The stranger eventually, is revealed as a serial killer on the run. Seeking revenge for his father, a son embarks on a journey in which he encounters a young girl by chance and starts to learn martial arts.