In writing the role of Jessica, Hancock sought to create a filmic equivalent to the unreliable narrator in literary fiction. Jessica was partly influenced by the governess in Henry James's novella "The Turn of the Screw", as well as the character of Eleanor Lance in Robert Wise's film "The Haunting" (1963). The theme of evil pervading the protagonist's mind was central: "I was alarmed by the notion that you can't defeat or defuse evil—it forever lives inside and all around us—so I worked that fear inside the story," said Hancock.