Caroline Ellis, a compassionate hospice worker disillusioned with her job, takes a position caring for Ben Devereaux, an elderly man left paralyzed and mute by a stroke, in his decrepit plantation house in rural Louisiana. The house is owned by Violet, Ben's enigmatic wife, who is committed to caring for him but is mysteriously secretive. Caroline quickly becomes unnerved by the strange atmosphere and Violet's peculiar behavior, but her concern for Ben motivates her to stay and help. Violet gives Caroline a skeleton key that opens all the doors in the house. Caroline's curiosity is piqued when she discovers a secret room hidden in the attic filled with mirrors, old records, and objects hinting at hoodoo, a form of folk magic.

Driven by the eerie occurrences she encounters and hoping to help Ben, Caroline begins investigating the house's past with the aid of her friend Jill and the sympathetic family lawyer, Luke. Her research leads her to learn about the previous owners—a pair of servants reputedly versed in hoodoo who met an untimely end. As Caroline digs deeper into the history and spells of hoodoo, she uncovers secrets about Violet, Ben, and the sinister forces possibly at play within the household. However, as she becomes more entangled in the supernatural undercurrents of the place, Caroline realizes that the reality is more disturbing than she could have imagined, bringing her to a terrifying revelation that challenges her beliefs and perceptions.