I Saw the Devil

Kyung-chul (Min-sik) is a maniacal serial killer who drives a yellow school bus and preys on young women. He captures and kills his victims, but their deaths are not the end of his madness. While the police have been aware of his actions for some time, they have never been able to put a name or face to his crimes.

When the corpse of a retired police chief's pregnant daughter surfaces, things change gears and the hunter quickly becomes the hunted. Yet it is not the girl's father who swears vengeance, but rather her secret agent fiancé, Joo-yeon (Byung-Hyun), who decides to track down the perpetrator himself. Anyone with even the remotest information on the killer's whereabouts is in for a bloody beating. But when his mission starts to come together, Joo-yeon morphs into quite a disturbing monster himself.