Soo-hyuk, an elementary school teacher in a rural village, has a secret. Every night, his wife Yi-young turns into another person. One day the father of one of his students comes to know of their secret and informs the village that Yi-young's body is possessed by a spirit each night. The townspeople conclude that Yi-young is dangerous, and install a cage in her home. They agree that every night, Yi-young is to enter the locked cage, and the student's father will take possession of the key. When the sun rises each morning, the father will return the key to Soo-hyuk. Unable to bear the thought of leaving his wife alone, Soo-hyuk too goes into the cage with her. That night, a fire starts inside the cage, and Soo-hyuk and Yi-young burn to death. The formerly quiet village is turned upside down by this fire incident.