Beware My Lovely (1952)
IMDb review: This is an experimental studio film from the early Fifties and was directed by Harry Horner, better known for his set designs. Robert Ryan plays a handyman who is hired by a widow, played by Ida Lupino, to do some housework for her. The problem is that he is a psychopathic murderer and doesn't know it. The woman is an empathetic soul and tries to win him over, to little avail. He is not the sort of man compassion could help or cure. Thus, we have an interesting situation of two people who basically mean well, but one of them can't do well because there is something wrong with him. He suffers periodic blackouts during which he commits acts of violence, which he later forgets. Essentially, the effect he has on her is that of hunter and prey. The audience finds out early on that he is a mad killer, but it takes her much longer. Thus we must live with this knowledge as we watch the poor woman try everything in her power to win him over in order to make things work, get the job done, get on with life. But getting on with things isn't in his makeup, as he is incapable of any but the most rudimentary forms of normality. As soon as there is an opening, his paranoia asserts itself.
TCM airs this occasionally.