The Skeleton Key

Caroline Ellis (Kate Hudson) is a New Orleans hospital aide who takes a position as a private hospice caregiver at an isolated plantation house deep in the bayous of southern Louisiana. The lady of the house, Violet Devereaux (Gena Rowlands), looks after her husband Benjamin Devereaux (John Hurt), a stroke victim who is expected to die soon. At first, Caroline is unsure about taking the job, as Violet is very hostile towards her, but with some prompting from the family's estate lawyer, Luke Marshall (Peter Sarsgaard), she accepts the position.

Caroline soon finds the mansion has a dark past. Finding her way into a secret room in the attic, she discovers dolls, a book of spells, potion jars, and other instruments of magic. Violet tells Caroline that the room belonged to two house servants who had worked at the house in the 1920s. Mama Cecile (Jeryl Prescott) and her husband, Papa Justify (Ron McCall) were renowned practitioners of hoodoo, a form of Afro-Caribbean folk magic. The couple, it is revealed, were lynched when it was discovered that they were performing spells with the children of the house owners.

In order to find answers about the ever-present hoodoo magic, which seems to be the root cause of Ben’s illness, Caroline goes to a local gas station where she earlier saw hoodoo artifacts. There, an old woman tells her of one of the most powerful hoodoo conjurations, the conjure of sacrifice. Caroline had discovered a record with this title on it and feels as though it had something to do with Ben’s illness. The old woman tells Caroline that this powerful spell is one of immortality, in which the caster sacrifices someone and gains the remaining years of their life. Caroline senses that Ben is in danger.

After a failed attempt to get Ben out of Violet's grasp, Caroline seeks the help of Luke. Luke is aware of Caroline’s suspicion of Violet. At Luke's house, Caroline discovers clues leading to the revelation that Luke is in league with Violet. Just as Caroline is about to act, Luke captures her, ties her up and gags her to take her back to the manor. Caroline is held captive but manages to get free and scatter brick dust throughout the house, which, according to hoodoo tradition, is meant to keep away those who mean one harm. This enchantment succeeds in keeping Luke away, but Violet gets to Caroline and blows a powder in her eyes (probably goofer dust) that distorts her vision. After a brief struggle, Caroline manages to push Violet down the stairs and breaks her legs. With Luke and Violet now downstairs, Caroline flees to the attic to find that the room has been set up for some kind of ritual. She follows the instructions on a piece of paper that she snatched from Violet earlier and forms a protective circle around herself. However, the protective spell was a trick intended to capture Caroline instead of protect her. Violet comes into the ritual room and explains that hoodoo magic only works on those that believe in it, and "they" have been waiting for her to believe. Caroline realizes that it was in fact she who was in danger and not Ben. Caroline tries to deny the fact that she now believes in hoodoo but cannot convince herself.

Violet pushes a mirror at Caroline, which initially contains the image of the little girl, then of Violet, and ultimately of Mama Cecile. The mirror smashes into Caroline, knocking her unconscious. Caroline then wakes up and walks over to Violet, who is barely awake. It is revealed that the soul of Mama Cecile is now inside Caroline's body, and Caroline's soul is now in Violet's body. Luke's body is revealed to be possessed by the soul of Papa Justify. Ben, who was previously the host to Papa Justify's soul, is revealed to be the real Luke.

Caroline/Mama Cecile gives Violet/Caroline a liquid that causes a pseudo stroke. This prevents her from talking so she can't reveal the presences of Mama Cecile and Papa Justify. When Caroline's friend Jill (Joy Bryant) arrives at the Plantation, Luke/Papa Justify informs her that "Ben" and "Violet" left the house to "Caroline," thus leaving Mama Cecile and Papa Justify to continue occupying the house. The film ends with Caroline and Luke looking at each other helplessly, trapped in Violet and Ben's bodies. When "Mama Cecile" and "Papa Justify" were lynched after performing the same spell with the children, it was actually the children who were lynched while occupying Mama Cecile and Papa Justify's original bodies, with Mama Cecile and Papa Justify actually living on in the children's bodies.