The story follows Grace, a 15-year-old isolated girl obsessed with religion. After attempting suicide, she is saved by a man and his partner. Grace discovers the partner is committing adultery, which leads Grace to stalk the woman in an attempt to purify her. As Grace's obsession grows, the woman, Gwen, believes she is being stalked but others think she is insane. Grace's religious mania escalates until she takes extreme measures, believing she is removing sin from the world.