"Alfred Hitchcock Presents"The Better Bargain (1956)

Mobster Louis "The King" Koster believes that his wife and sole heir is unfaithful. He hires a hit man to kill her for twenty thousand dollars. The hit-man agrees, but he then shoots Koster dead. The hit-man was Marian's lover. Since she will inherit everything, the hit-man decided to go with the better bargain.