A wealthy 18-year-old girl, Ava, selects a maid named Hilary, after which her mother, Tina, suddenly begins favoring the maid, stripping Ava of her inheritance and subjecting her to harsh treatment. Convinced her mother is under a spell, Ava attempts to gather evidence but is repeatedly misunderstood, even forbidden from attending school and forced to give up her bedroom. When her father, Blair, returns home, Ava discovers his affair with Hilary and their plot—they plan to use "dark magic" to control Tina and kill Ava to seize the family fortune. During an elaborately staged attempt on her life, Tina suddenly reveals the truth: she had been playing along, pretending to be controlled to gather evidence. The antagonists are ultimately arrested, and the mother and daughter use their wisdom and love to resolve the family crisis.
