When Blatty was a student at Georgetown University in 1949, he read newspaper accounts of an exorcism performed on a boy in the D.C. suburbs. He never forgot them; by 1973, they had laid the groundwork for his bestselling book and Oscar-winning movie.

Blatty set his exorcism in Georgetown and made his victim a young girl. In the film, she lived--and levitated and spewed vomit--with her mother in an imposing brick house at 3600 Prospect Street, NW (Blatty had lived on that street during college). Just a short walk away is the famous outdoor stairway that Father Damien Karras tumbled down to his death. The house is private, but the steps are very public, linking Prospect to the busy thoroughfare of M Street, NW.