Luchino Visconti's first film, Ossessione, is based on James M. Cain's The Postman Always Rings Twice. I haven't read the book or watched the 1946 movie version by Tay Garnett, so I can't compare.
The beautiful Giovanna is unhappy with her marriage with the fat, dirty, but rich Bragana in Ferrara. Enters Gino, a handsome tramp, who works temporarily for Bragana. Giovanna and Gino fall in love to each other and plan to murder the husband. The police have their suspicion, and the guilt after makes both Gino and Giovanna realize that life is not as beautiful as they have dreamed.
Giovanna marries Bragana because she wants a home. Gino is a tramp who cannot easily stay in one place for a long time. She refuses when he asks her to go away with him, to leave the husband she hates. Love is one thing, but Giovanna sees the reality of life. She cannot leave her comfortable home. She cannot live like Gino. After the murder, Gino has to stay with her and this makes him miserable. When she tells him that Bragana has a life insurance, Gino thinks that she has drawn him into the mess, and now he has blood in his hands. [This is very interesting, especially after watching new movies where people seem to kill without blinking.] He reconciles with her, after she told him that she is pregnant his child. With the police in tail, she finally agrees to leave with Gino, but they have a car accident.