Fan Casting I Saw the Devil (1974)

On a dark road, taxi driver Kevin James comes across a scared female motorist stranded in a broken-down vehicle. He pulls over, but not to help her. Instead, he kidnaps, rapes, and kills her. When the woman's head is discovered in a local river, her devastated fiancé, Shaun Kennedy, a trained secret agent, becomes obsessed with hunting down her killer. Once he finds Kevin, things get twisted. After brutally beating the murderer, Shaun lets him go free, and a demented game of cat and mouse begins where at first Shaun believes this will make up for that he wasn’t able to save his fiancée, but slowly goes on a journey to madness.