Prey for revenge. I Saw The Devil is a shockingly violent and stunning tale of murder and revenge. The embodiment of pure evil, Kyung-chul is a psychopath who kills for pleasure. His latest victim was not only the daughter of a retired police chief, but also the pregnant fiancée of elite special agent Soo-hyun. Obsessed with revenge, Soo-hyun is determined to track down the murderer, even if doing so means becoming a monster himself. Turning Kyung-chul in to the authorities is the last thing on Soo-hyun's mind, as the lines between good and evil fall away in this diabolically twisted game of cat and mouse.