In the late 1950’s up to the late 1960’s (I think it was black and white, so I’m leaning to the earlier date), I saw a movie where the widow comes home to the huge mansion where she lived with her husband, only to find that all the servants, lawyers, etc., are claiming he’s still alive. I think they had a man pretending to be the husband. All through the movie, you feel so upset that she’s being tormented this way, gaslighted I’d call it, until, at the end, she’s so overwrought that she finally screams out that she knows her husband really is dead, because she killed him. That was the whole point of the setup—to get her to confess. It was a great twist, because you were on her side right until the denouement.