Ji-woon Kim directs the aptly titled vengeance tale I Saw the Devil. The two main characters learn about the devil in themselves by looking at one another.
Kyung-Chul (Min-sik Choi) murders women. Resilient and wily, he is also so insane that he is almost hapless in his understanding of the world. One winter's night, he butchers Joo-Yeon (San-Ha Oh), a young woman who is pregnant by her fiance Kim Soo-hyeon (Byung-hun Lee). Joo-Yeon's detective father feels guilty for not being able to protect his own daughter, but he tries to be thankful for at least finding her dismembered body. He and his other daughter find space in their grief to worry about Soo-hyeon.
Kyung-Chul (Min-sik Choi) murders women. Resilient and wily, he is also so insane that he is almost hapless in his understanding of the world. One winter's night, he butchers Joo-Yeon (San-Ha Oh), a young woman who is pregnant by her fiance Kim Soo-hyeon (Byung-hun Lee). Joo-Yeon's detective father feels guilty for not being able to protect his own daughter, but he tries to be thankful for at least finding her dismembered body. He and his other daughter find space in their grief to worry about Soo-hyeon.
A skilled special agent, Soo-hyeon takes it upon himself to find the killer. We follow both Soo-hyeon and Kyung-Chul as the former brutalizes suspects and the latter prowls for more victims. When Soo-hyeon finds Kyung-Chul, he abuses him to near death before pulling back and leaving him money. With the help of an implanted tracking device and microphone, Soo-hyeon later finds Kyung-Chul so he can repeat the torture.
Kyung-Chul mentions his strange stalker to an equally mad friend, who points out that his pursuer is enjoying the hunt in the same way they do. Kyung-Chul contemplates this and begins to enjoy his and Soo-hyeon's symbiotic relationship. Soo-hyeon's sister-in-law tells him that there is no meaning in taking revenge on a crazy man. Soo-hyeon claims there is, and the audience wonders when he will deem the punishment complete.
Touches of ironic humor are sprinkled throughout the film. The deranged killer calls others "crazy retards" or "psychos." One scene shows his reluctance to get into a taxi after he has lured so many women into his vehicle.
For those who don't love gore, this film is nauseatingly violent. The protagonist's brutality is shown more graphically than the criminals'. Due to excessive blood-letting and lingering shots on defenseless women, the message that retribution calls forth an unwelcome monster is difficult to take seriously. However, the film's final minutes are chilling. The grisly action pauses long enough for us to witness what is within the two men. I Saw the Devil's harrowing conclusion powerfully examines the pointlessness of sadism.
