Bluebeard (2017)

Dr. Seung-hoon (Jin-woong Cho) sedates his landlord before medical check-up, when the old man begins telling him a convincing murder confession. Sometime later, a young woman's severed head is discovered at a butcher shop run by his landlord's son, and Seung-hoon begins to suspect that the landlord and his son are the serial killers.