I Saw the Devil

I Saw the Devil (Korean: 악마를 보았다) is a 2010 South Korean action thriller film directed by Kim Jee-woon and written by Park Hoon-jung. Starring Lee Byung-hun and Choi Min-sik, the film follows NIS agent Kim Soo-hyun (Lee), who embarks on a quest for vengeance when his fiancée is brutally murdered by serial killer Jang Kyung-chul (Choi).

I Saw the Devil marks Choi Min-sik's first major role since the changes to the Korean screen quota system. The film premiered in the United States at the 2011 Sundance Film Festival and had a limited U.S. theatrical release, where it received generally favourable reviews from critics who praised its cinematography, cast performances and action sequences but criticized the graphic violence.

Jang Kyung-chul, a school bus driver, encounters a woman named Jang Joo-yun and offers to fix her flat tire. After beating her unconscious and bringing her to his house, Kyung-chul methodically dismembers her, unaware of her ring falling into a floor drain. Kyung-chul scatters the body parts into a local river, where it is discovered, prompting the police to conduct a search led by Squad Chief Jang, Joo-yun's father, and Squad Chief Oh. Joo-yun's fiancée, Kim Soo-hyun, an NIS agent, vows to exact revenge on the perpetrator.

After learning of the four suspects from Jang (Joo-yun's father), Soo-hyun privately interrogates two of them. The violent encounter (part torture) of the first two suspect absolve them as his wife killer. But they are not without fault, one suspect turn himself in for killing multiple schoolgirl in fear of Soo-hyun return and seeking help from the police in the hospital. Upon searching the home of Kyung-chul (the third suspect), Soo-hyun finds Joo-yun's ring which confirms Jang Kyung-chul to be his fiancé killer.

A short time later, Kyung-chul brings a schoolgirl home and begins to rape her. Soo-hyun interrupts and knocks him unconscious. Instead of killing Kyung-chul, Soo-hyun forces him to swallow a GPS tracking transmitter, allowing him to track Kyung-chul's movements and listen to his conversations and fracture his left arm.

Waking up, Kyung-chul is offered a ride by a taxi, which already carries a passenger. The taxi had a license with a profile picture of the taxi's owner, which Kyung-chul notice is not the one driving this taxi. He has step into a hijacked vehicle and the occupants is acting strange. Kyung-chul attacks seconds before they attacked and murders them. Kyung-chul check the boot of the taxi and found a murder victim (presumably the taxi driver) and a bag of fresh clothes. He leaves their bodies on the side of the road, and cleans up in a nearby river.

Kyung-chul drives to a clinic to have his wounds looked at. After being treated, Kyung-chul proceeds to rape a nurse. Soo-hyun arrives, subdues him, and slashes his achilles tendon before leaving. At this point, Soo-hyun's intention becomes clear: he wants to torture Kyung-chul as long as possible. Kyung-chul visits the home of his friend Tae-joo, a cannibalistic murderer and meet his girl friend Se-jung who seems nonchalant about the meeting.

After learning of the situation, Tae-joo remarks that his tormentor must be related to one of his victims. Kyung-chul deduces Soo-hyun's identity after recalling that his wedding ring matched that of Joo-yun. Soo-hyun arrives and incapacitates Kyung-chul, Tae-joo, and his girlfriend Se-jung. The next day, Tae-joo and Se-jung, still unconscious, are arrested by the police and sent to the hospital. Soo-hyun and Kyung-chul receive treatment for their wounds, aided by Soo-hyun's trusted subordinate, who helps them evade the cops. Kyung-chul wakes up and overhears Soo-hyun and the subordinate talking about the transmitter.