By day, Ha-Rin is a sculptor and teacher. By night, she turns into the serial killer Sow who, along with her protege Soon-Hee, uses a chat app to ensnare men with sex. After the deed is done, the men are kidnapped and tortured to death, punishment for being adulterers or for using women as if they're objects. But Detective Kim and his team are on these murderers' trails - will the duo's reign of terror be stopped?