After her parents' separation, Margot, a rebellious pre-teen, sets herself the challenge of reuniting her family. One day, returning home from school, she discovers to her horror that a stranger has moved into her house and seems to have bewitched her father. Increasingly disturbed by the inexplicable phenomena surrounding this strange stepmother, Margot is convinced she's dealing with a truly evil witch. Determined to save her family, Margot seeks out Miss Dalloway, a self-proclaimed expert in the occult, hoping she can help her get rid of the intruder who has taken her family hostage.