I Saw The Devil is a South Korean thriller directed by Kim Jee-woon. The narrative follows a secret agent who embarks on a relentless and personal quest for vengeance after his fiancée is brutally murdered by a psychopathic serial killer. The film stars Lee Byung-hun and Choi Min-sik, and is renowned for its intense and gritty portrayal of the cat-and-mouse game between the two central characters.