Anthony Perkins plays a doctor who wants to kill the lover of his cheating wife (Jill Ireland). He concocts a plot to convince an amnesia patient (Charles Bronson, in a very offbeat role), that the doctor's wife is really the amnesia patient's wife. Confused, jealous, and angry, Bronson is drawn into the murderous plot.
This isn't a great movie, and I wish it had a better ending, but it's pretty good and it's nice to see Bronson in a role other than a vigilante or a cop. Most of the movie takes place in Perkins' home, so it could easily be converted into a stage play. You might want to give this one a try.