Bluebeard

Following the failure of his Gangnam clinic and divorce, Physician Seung Hoon moves to the countryside, into an area infamous for serial murders, to work in a private clinic. One day while doing a colonoscopy on his landlord’s elderly father, Seung Hoon hears the old man talking about murder while under anesthesia. Soon, a woman's severed body is discovered in the Han river, and Seung Hoon starts suspecting his landlords when he sees what looks like a human head in their butcher shop.
(Source: MDL)