"I Saw the Devil" is a South Korean psychological thriller film directed by Kim Jee-woon. The movie stars Choi Min-sik and Lee Byung-hun in the lead roles. The film's plot revolves around a prosecutor named Soo-jin (played by Choi Min-sik) who becomes obsessed with seeking revenge against a serial killer named Kyung-min (played by Lee Byung-hun) after his fiancée is brutally murdered.