I Saw the Devil () 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 of revenge when his fiancée is brutally murdered by the psychopathic serial killer Jang Kyung-chul (Choi). 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. I Saw the Devil was Choi Min-sik's first major role since the changes to the Korean screen quota system. Plot One night, a school-bus driver named Jang Kyung-chul encounters a pregnant woman named Jang Joo-yun and offers to fix her flat tire. After beating her unconscious, Kyung-chul dismembers Joo-yun at his home, and while doing so, Joo-yun's ring falls. Kyung-chul ignores it and scatters the body parts into a local stream. When a boy discovers one of Joo-yun's ears, the police arrive en masse to conduct a search, led by Section Chief Oh and Squad Chief Jang, Joo-yun's devastated father. The victim's fiancé, Kim Soo-hyun, an NIS officer is also present and vows to take revenge against the murderer. Soo-hyun learns of the four suspects from Squad Chief Jang and proceeds to privately torture and interrogate two of them. Upon searching the home of Kyung-chul, the third suspect, Soo-hyun finds Joo-yun's engagement ring, proving that Kyung-chul was the perpetrator. A short time later, Kyung-chul brings a schoolgirl home and assaults her. Soo-hyun beats him unconscious. Rather than killing Kyung-chul and being done with it, Soo-hyun decides to shove a GPS tracker down his throat, allowing him to see Kyung-chul's location in real time and to listen to his conversations. Waking up injured, Kyung-chul walks along the road and is offered a ride by a taxi already containing one passenger. Upon getting in, and correctly guessing that the driver and passenger are in fact two bandits intending to rob and murder him, one being Soo-hyun's unvisited fourth suspect, he strikes out preemptively and kills them both. Afterward, he finds the body of the real taxi-driver in the trunk. Kyung-chul throws out all three bodies, and drives to a small town where he sexually assaults a nurse. Soo-hyun arrives to subdue him and slashes his Achilles tendon before releasing him once more. Kyung-chul visits the home of his friend Tae-joo, a