The Alfred Hitchcock Hour - Season 2 Episode 12 Three Wives Too Many

Brown is a chronic gambler and bigamist who starts to run out of money when his wealthy wives start turning up dead. The police suspect that he is responsible for murder, but when no evidence turns up they are forced to conclude that each death was a suicide. The real murderer is one of Brown's wives who jealously wants to keep her husband all to herself. She tells him that if he strays again she will commit suicide and she will arrange for him to be charged for her murder and the murders of his other wives.