Remake based on Kim Jee Woon's 2010 South Korean thriller "I Saw the Devil." In the 2010 Korean original, "Oldboy's" Choi Min-sik plays Kyung-chul, a dangerous psychopath who kills for pleasure. The embodiment of pure evil, he has committed horrifying and senselessly cruel serial murders on defenseless victims, successfully eluding capture by the police. His latest victim is the beautiful Ju-yeon, pregnant fiancée of elite special agent Soo-hyun ("The Good, The Bad, The Weird's" Lee Byung-hyun). Obsessed with revenge, Soo-hyun decides to track down the murderer, even if doing so means becoming a monster himself. And when he finds Kyung-chul, turning him in to the authorities is the last thing on his mind. The lines between good and evil fall away in this diabolically twisted game of cat and mouse.