While investigating the kidnapping and murder of a little girl, a detective spots a piece of graffiti that depicts the crime scene perfectly—but the graffiti was drawn a month before the crime took place, and that the artist knows more than he is telling.

A detective infiltrates into one of the biggest gang organizations in the country and gets involved in a fight for the heir to the gang after the boss dies and in between the second in charge who trusts him with his life and the high police officials who think of him only as bait.

Kyung-chul is a dangerous psychopath who kills for pleasure. He has committed infernal serial murders in diabolic ways that one cannot even imagine and his victims range from young women to even children. The police have chased him for a long time, but were unable to catch him. One day, Joo-yeon, daughter of a retired police chief becomes his prey and is found dead in a horrific state. Her fiance Soo-hyun, a top secret agent, decides to track down the murderer himself. He promises himself that he will do everything in his power to take bloody vengeance against the killer, even if it means that he must become a monster himself to get this monstrous and inhumane killer.