SPOILER: In the scene where Dom is attacked by the killer in the stairway at the abandoned building, it was required for the killer to drop the knife after stabbing Dom once and have it land directly on the handrail below, sticking straight up. Director Alfred Sole only had one knife and had to drop it repeatedly, and then have a crew member run back down the stairs to retrieve it and try it all over again. Finally, after over 20 tries, the knife landed directly on the handrail, giving the filmmakers the shot that was needed.
Brooke Shields's first movie.
Was partially inspired by the film Don't Look Now (1973), especially the usage of the yellow raincoats.
The knife used in the film was created by Alfred Sole's neighbor, who was an engineer, and was designed with a retractable blade. It was the only knife used in the film; the filmmakers never made any duplicates.
Linda Miller was injured while filming the scene in the hospital, and production had to be halted for a month. Fortunately, she didn't have to go far for medical help since they were filming in a hospital.
Father Tom drives a 1957 Ford Fairlane.
When Father Tom stands in the rain, watching Mrs. Tredoni check the mail, a poster for the film Psycho (1960) can be seen in the background.
Paula E. Sheppard, who played 12-year-old Alice, was 19 during the making of the film.