Setting: California during the Gold Rush, circa 1849
Inside the Polka Saloon near a mining camp The miners relax, playing a game of faro after a day of hard work. Sheriff Jack Rance observes the gloomy demeanor of one homesick miner, Larkens. Jake Wallace sings a nostalgic song. Larkens breaks down into tears, and the men agreed to create a fund to send him home. Sid is accused of cheating, and as the others are about to string him up, Rance throws him out of the saloon.
Mr. Ashby, a Wells Fargo agent, enters exhausted from his search for Ramerrez, a bandit he has been pursuing for three months. They all toast Minnie, the feisty barmaid, whom Rance believes he loves. Sonora disagrees and the men trade insults. A revolver is accidentally discharged. The miners calm down and offer modest gifts to Minnie. She, in turn, gives an impromptu Bible study, but is interrupted by the arrival of the Pony Express. As the mail is distributed, Ashby asks the rider about the location of Nina Micheltorena, assumed to be Ramerrez’s girlfriend, who would likely know the bandit’s whereabouts.
After the miners move into the next room, Jack professes his undying love to Minnie, which she rebuffs. She likes her life the way it is and envisions the domestic bliss of her childhood, a union much like the deep love that her parents once shared.
Dick Johnson enters, looking for a glass of whiskey and a game of baccarat. He lightly flirts with Minnie, recalling a brief moment they once shared. Angered, Rance demands to know what business he has in the camp. The miners reenter and suggest a dance, and Johnson and Minnie waltz into the ballroom.
Ashby enters with Castro, whom he accuses of being a member of Ramerrez’s gang. Castro claims he ran away from the outlaws, but is secretly luring the men away supposedly to show his former boss’ hideout so that Johnson (really Ramerrez) can hold-up the saloon. Johnson and Minnie exchange pleasantries. He ignores the signal from Castro to commit the robbery and agrees to meet Minnie at her mountain retreat.
Minnie’s cabin Wowkle sings a lullaby to her child as she and Billy Jackrabbit consider marriage. Minnie enters and requests dinner for two. She prepares herself for Johnson’s impending visit. When he arrives, he tries unsuccessfully to kiss her. Minnie questions Johnson’s motives for being in the camp. She goes on to describe her happy life on the mountain and at the camp. Johnson tries to embrace her again, and she relents. A blizzard makes it impossible to leave, and he agrees to spend the night. A knock at the door reveals Rance and the others in hot pursuit of Remerrez, who is posing as Dick Johnson. The bandit hides himself while Minnie sorts out the situation. Nina has given up her former boyfriend’s location, and Minnie learns he had intended to rob her saloon. Rance spies one of Johnson’s cigars and realizes he is nearby.
After the posse leaves, Minnie berates Johnson for his deception. He defends himself – his father died at an early age, and thievery is the only way he could support his mother and brothers. Once he met Minnie, he couldn’t go through with the robbery. He believes he can change his ways, if she can only give him her love. Still angry, Minnie throws him out. A shot rings out and Johnson reenters, wounded. Now recognizing her affection for him, she insists that he hide in the loft. Rance returns, certain that Johnson is concealed somewhere on the premises. A drop of blood betrays the outlaw’s presence, but he has fallen unconscious. Minnie decides that the matter shall be decided by a game of poker. If she wins, Johnson will remain free. If not, she will submit to Rance. After two hands, they are even, but during the third, when the sheriff’s back is turned, Minnie cheats to win. Rance storms away.
In the California forest As the rest of the party sleeps nearby, Nick tries to console Rance. When Ashby and the miners finally awake, they are certain Johnson has been discovered and hasten to the other side of the mountain to join the Wells Fargo men. Rance relishes his revenge. A bloodied Johnson is brought forth and accepts his fate. As they prepare to string him up, the miners accuse him of various murders, which he denies. Before they execute him, Johnson asks for a final request – Minnie must be told he has escaped and is on his way to a better life.
As he is about to be hanged, Minnie rushes in and demands mercy for Johnson. When her pleas are ignored, she threatens to shoot herself as well as the bandit. She reminds them of all she has done for them in the past. The miners are moved and release Johnson. Together the lovers ride off.