This is a really old psychological thriller, possibly from the 1950s. A woman (who may or may not have been in love with the man) comes to his house to find that he's married. She meets the wife who's taking care of her husband (unseen for the moment) and an old woman in a wheelchair. In one moment, there is a silhouette of the old lady moving slowly down the stairs via some electrical device. When she reaches the bottom, her head falls off in silhouette. The wife threatens the woman with a knife and she starts screaming for her male friend. Then the knife wielder tells her in a man's voice that "He" is here. The killer starts pulling off a wig and eyelashes (I think) and reveals that she is really a he. The film ends with a narrator warning not to tell the secret of the movie or the viewer will be killed.