Aspects of the novel were inspired by an exorcism performed by the Jesuit priest, Fr. William S. Bowdern, who formerly taught at both St. Louis University and St. Louis University High School. Recent investigative research by freelance journalist Mark Opsasnick indicates that this was the real 1949 exorcism of a young boy from Cottage City, Maryland, whom Opsasnick refers to using the pseudonyms Robbie Mannheim and Roland Doe. The boy was sent to his relative's home on Roanoke Drive in St. Louis where most of the exorcism took place.