 A number of collaborating writers also assisted, including Alex Rebar, Giorgio Marini, Aldo Crudo, and Christopher Cruise.The interior shots were filmed on set in Italy at the Incir De Paolis Studios in Rome, while all exteriors were shot on location in San Francisco.Detailing a woman possessed by a demon, "Beyond The Door" was labeled a rip-off of "The Exorcist" (1973).