A group of high school students is visiting a certain cave on a field trip. A small group of them enters a corridor leading away from the main cave... but one of them, Tomoko, is ultimately left alone. After a few moments, she hears the screams of her classmates from deep inside the cave.

Haruko moves to a village in the countryside to live with her new husband's family, On the way, he tells her about a custom in the village that requires its residents to toss their most prized possessions into a swamp. Shortly after they arrive at his family's home, Haruko is forced to join in this ritual with the rest of the villagers.