I Saw the Devil

I Saw the Devil Hangul RRAngmareul boatda is a 2010 South Korean psychological thrillerhorror film directed by Kim Jeewoon, written by Park Hoonjung, and starring Lee Byunghun and Choi Minsik. The film introduces the character of NIS agent Kim Soohyun Lee Byunghun, who embarks on a quest of revenge when his fiance is brutally murdered by a psychopathic murderer, Jang Kyungchul Choi Minsik. The line between good and evil begins to blur when the two play a dangerous game of cat and mouse. I Saw the Devil made its premiere in the United States at the 2011 Sundance Film Festival and had a limited U.S theatrical release. The film was Choi Minsiks first major role since the changes to the Korean screen quota system. It has received generally positive reviews with praise towards the acting, direction, cinematography and script.

Jang supplies Soohyun with a list of four suspects, including Kyungchul. Searching Kyungchuls home, Soohyun finds jewelry and underwear taken from apparently numerous victims. The discovery of Jooyuns engagement ring proves that Kyungchul is the killer. Soohyun puts a tracking device on the academy bus, following then attacking Kyungchul while he is sexually assaulting his latest victimone of the schoolgirls he was transporting home. Beating him unconscious, Soohyun places an NIS transmitter inside Kyungchul, allowing him to track him on radar and listen to his conversations. Waking up, Kyungchul flags down a taxi. During the ride, Kyungchul realizes that the two men in the cab are thugs looking to rob and possibly kill him he stabs both men to death. After finding the real taxi driver in the trunk, Kyungchul disposes of all three bodies before going to a medical center, where he attempts to sexually assault a nurse Han Songyi. Soohyun intervenes and slashes Kyungchuls Achilles tendon before letting him go again.Kyungchul goes to the home of his friend Taejoo, a cannibalistic murderer. After explaining his situation, Taejoo remarks that whoever is after him must have some relation to one of his victims. Soohyun arrives, proceeding to incapacitate both murderers along with Taejoos girlfriend Sejung. The next day, both Taejoo and Sejung are found by the police and sent to a hospital. A trusted subordinate of Soohyuns ensures he and Kyungchul are sent to a private medical area away from the police. The barely conscious Kyungchul hears them talk about the transmitter inside him. ........

Source: Wikipedia