After her parents separate, Margot, a teenager searching for her identity, sets herself the challenge of reuniting her family. One day, returning home from school, she is stunned to discover that a stranger has moved in and appears to have bewitched her father. Margot, increasingly troubled by the inexplicable phenomena surrounding this strange stepmother, is convinced she is dealing with a real evil witch. Determined to save her family, Margot calls on Mrs. Dalloway, a self-proclaimed occult expert, hoping she can help her get rid of the intruder who has taken control of her home.