The Secret of the Whistler - 1946 (richard dix, leslie brooks, michael duane)

An artist married to a wealthy but ill woman begins an affair with one of his models, who is after him solely for his money. His wife discovers the affair and threatens to cut him out of her will. In order to be able to keep both the wife's money and his girlfriend, he begins to secretly poison his wife - but events take a surprising turn after she eventually dies.