I first saw this movie in 1977 when it was rented by my family on the Super 8mm film format. I was glad to watch it again recently as a trip down memory lane. I did enjoy the film (apart from the irreverent use of the name of the Lord Jesus). There are two distinct clues given as to the identity of the murderer (that I picked up). The suspect lot is not large as the story plays out in one location. In my opinion it falls in the genre of the television series Murder She Wrote and is entertaining with a mild suspense build up.
Review of The Spiral Staircase
