Kyung-chul is a dangerous psychopath who kills for pleasure, his victims ranging from young women to children. The police have chased him for a long time, but have been unsuccessful. One day, Joo-yeon, daughter of a retired police chief becomes his prey and is found dead in a horrific state. Her fiance Dae-hoon, a top secret agent, decides to track down the murderer himself. He will do everything in his power to take bloody vengeance against the killer, even if it means becoming a monster himself.