John Wayne plays Duke Fergus, a good-hearted rancher from Montana who comes to San Francisco to collect a debt owed to him by Tito (Joseph Schildkraut), slick owner of a casino. He falls in love with Flaxen (Ann Dvorak), the beautiful saloon singer engaged to Tito. Duke loses his hard-earned bankroll at Tito's casino forcing him to leave town. But not for long! The next time he comes to town, his luck radically changes. In fact, he's so lucky that he almost cleans out Tito's casino. With his winnings, Duke builds a casino across the street from Tito, hiring Flaxen as his opening night headliner. All goes well until the great San Francisco earthquake forces Duke, Flaxen and all the residents of the city to regroup and rebuild.