A mining camp at the foot of the Sierra Nevada Mountains in California, 1849-1850. As Nick, the bartender of the “Polka,” pours drinks, the miners gamble, listen to the camp’s minstrel, Jake Wallace, and take up a collection to send home one of their homesick companions, Larkens. Handsome catches Sid cheating at faro; Sheriff Jack Rance’s intervention prevents a lynching. Ashby, the agent of Wells-Fargo, tells Rance that he has new information which will enable him to capture the bandit Ramirrez and his band of cutthroats. Rance’s boasting that Minnie, the owner of the Polka, will soon be his wife provokes a fight, and it is Minnie herself who separates the men. After reprimanding them she begins her regular Bible lesson, which is interrupted by a courier arriving with mail and the news that one of the bandits has been sighted nearby. Rance tells Minnie he loves her and asks her to marry him. She reminds him with humor that he already has a wife and explains with sincerity the kind of love she hopes to find. When the stranger, “Johnson from Sacramento,” enters, Rance resents the welcome Minnie extends to him. Minnie and Johnson have recognized each other immediately; once they are alone, they recall a pleasant afternoon spent together after a chance meeting on the road to Monterey. Rance calls in the miners, determined to get rid of his rival. The men invite Johnson to dance with Minnie. Ashby enters with Jose Castro, one of the outlaws, under guard. When Castro sees his boss Ramirrez (alias Johnson) dancing, he sends Ashby and the posse off on a wild goose chase. Before he is led away, he manages to tell Johnson that the bandits are nearby awaiting his signal to rob the Polka. Minnie asks Johnson to stay after the others have left. A shrill whistle, which Johnson recognizes as the signal, frightens Minnie. She confides in Johnson that she alone must now protect the gold the miners have entrusted co her. She vows that whoever takes it must kill her first. Johnson decides to stop the robbery. They agree to meet later at her cabin in the mountains.

As a blizzard rages outside Minnie’s cabin, Wowkle, Minnie’s Indian servant, sings a lullaby to her infant. Billy Jackrabbit enters and carries out Minnie’s orders by asking the girl to marry him. Minnie comes in and makes hasty preparations to receive Johnson. Johnson is soon hospitably received and sharply rebuffed for an attempted embrace. Minnie tells him that she loves her life and her role as teacher to the miners. She offers him a cigar, then dismisses Wowkle. When they are alone, Johnson tells Minnie he has loved her since their first meeting. Because of a raging blizzard, Minnie offers him her bed and prepares a place for herself in front of the fire. There is a loud knocking and, from outside, Nick’s voice announces that Ramirrez has been seen on the trail to Minnie’s cabin. Johnson hides behind the curtains and Minnie opens the door. She receives a double shock when she learns that Johnson is Ramirrez the bandit and that he is the lover of a Mexican woman who has betrayed him by giving his photograph to Rance, who gloats as he shows it to her. When Rance has left, Minnie confronts Johnson. He tries to defend himself, but Minnie orders him out.

Seconds later gunfire is heard and the sound of a body falling against the door. Minnie opens it and finds Johnson wounded. Despite his protests, she helps him inside and hides him in the loft. Rance reappears in pursuit of Johnson. When Minnie tells him there is no one with her, Rance abruptly makes violent advances, which Minnie repulses. Suddenly a drop of blood falls on his hand and he realizes the fugitive is hiding in the loft overhead. He calls up to Johnson co come down and the order is obeyed. Johnson seats himself at the table and collapses. Desperate, Minnie proposes a game of poker. If Rance wins, he takes Johnson and her; if she wins, Johnson is hers. Rance agrees to the stakes. At the final hand Rance exultantly throws down three kings. Nearly fainting, Minnie asks for a drink. While Rance is distracted she substitutes cards for the ones Rance has dealt. When he brings her the whiskey, she displays the cards in her hand: three aces and a pair. Dumbfounded, Rance keeps his word and stiffly departs.

One week has elapsed. Rance, Nick and some of the miners are waiting while Ashby and the others track down Johnson in the hills. True to his word, Rance has not betrayed Minnie. Singly and in groups, the miners rush into the camp to report the progress of the manhunt. Finally, Ashby appears with Johnson and formally turns his prisoner over to Rance. As the miners shout at Johnson a list of his offenses, they prepare a noose. Rance offers him a last chance to speak before the execution. Johnson asks the men to let Minnie believe he is free and far away. Minnie rushes in with a drawn revolver. Urged on by Sonora, one by one they agree to grant Minnie’s request. Minnie and Johnson say goodbye to the miners and disappear over the horizon.