Love is the key to redemption

One of the themes of the movie is how love is tied to redemption. Both Dad (Malden) and Rio (Brando) are criminals, but both inwardly desire redemption and a better life. The love of Dad's wife (Katy Jurado) and the Monterey general populace brings this out in Dad, whereas Louisa's love for Rio slowly changes him. Near the end we plainly see that Rio no longer wants to kill Dad, he doesn't even want to see him again; all he wants is to run off with his lady love. (If Rio remained the same lying criminal he was at the beginning of the story "One-Eyed Jacks" wouldn't be half the film it is).

In addition, Dad's love for Katie, his Mexican wife, is what delivered Katie and Louisa "from the beanfields," as Dad puts it.

Love goes hand-in-hand with loyalty or faithfulness. We see this in Rio's likable Mexican sidekick, Chico (Larry Duran).