The Alfred Hitchcock Hour (1962)

Oscar Blenny is a timid bank clerk who discovers that his wife Eva is cheating on him. He demands a divorce and Eva agrees, but insists on a $50,000 settlement. She tells him to steal it from the bank, but Oscar is reluctant. Oscar is approached by Eva's tough hitman boyfriend Bill Grant. Bill suggests a double-cross. He will kill Eva for $250,000, but will get the money by robbing Oscar's bank with Oscar's help. He will then leave the country and leave Oscar free of Eva and apparantly innocent of any crime. Oscar agrees to Bill's plan, but sets up a triple-cross. Bill kills Eva, but when he comes to rob the bank Oscar pulls a gun and shoots him dead. Impressed by Oscar's courage, his boss promotes him to credit manager.