The Two Mrs. Carrolls

A painter tries to murder his second wife in the same way in which he killed his first, through slow poisoning, when he becomes attracted to neighbour Cecily Latham who threatens to end their affair unless he comes away with her. However, his wife is suspicious of her illness and realises what is happening. She manages to phone for help just before her husband attacks and tries to strangle her, and the police arrive in time to save her and arrest him.