I Saw the Devil

Kyung Chul is a dangerous psychopath who terminates for pleasure. He has committed infernal serial tragic ends 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 fianceSoo Hyun, a top-secret agent, decides to track down the criminal himself. He promises himself that he will do everything in his power to take bloody vengeance against the criminal, even if it means that he must become a monster himself to get this monstrous and inhumane criminal.