In Reno, Nevada, Roslyn Tabor (Marilyn Monroe), is a beautiful 30-year-old woman having just divorced her unattenative husband Raymond (Kevin McCarthy). At a bar, Roslyn meets aging cowboy Gaylord 'Gay' Langland (Clark Gable) and his best friend Guido (Eli Wallach). Gay and Guido invite Roslyn and her friend Isabelle Steers (Thelma Ritter) to Guido's place in the country to help her forget about the divorce. They arrive at the half-finished house Guido built for his wife, who had died 10 years earlier during childbirth. They drink and dance. Roslyn has too much to drink, so Gay drives her home to Reno.
Eventually, the two move into Guido's half-finished house and start to work on it. One day after breakfast, Gay tells Roslyn how he wishes he were more of a father to his own children, whom he has not seen for some years. Later that afternoon, Roslyn and Gay have a fight when he decides to kill a rabbit that is eating from the vegetable garden they have planted.
When Guido and Isabelle show up at the house, Gay suggests rounding up wild mustangs (horses) to sell and make a profit from it. They go to a local rodeo to look for and hire a third man for the job. Along the way, they meet Perce Howland (Montgomery Clift), a wayward friend of Gay's who is on his way to the rodeo to compete. Gay offers to pay for the broke Perce's entry fee if he helps them with the mustangs afterward. Perce agrees.
At the rodeo, Roslyn becomes upset when Guido tells her how the horses are made to buck with an irritating flank strap. She declares that all rodeos should be banned. Later, after Perce is thrown by a horse, Roslyn begs him to go to a hospital, but he insists on riding a bull. He gets thrown again, resulting in a head injury.
Later, after Roslyn dances with Perce, he passes out in a back alley from his head injury. When he regains consciousness, he sees her crying over him. He says that he never had anyone cry for him before and that he wished he had a friend to talk to. He tells her all about his unhappy childhood and how his mother changed after his father died. His mother remarried and gave his stepfather the ranch his father wanted to leave to Perce. Just then, a drunken Gay then fetches Roslyn, telling her that he wants her to meet his kids, whom he unexpectedly ran into. But Gay causes a public scene when he discovers his children have not waited around.
Later on, during the drive home, a drunken Guido asks if Roslyn has left Gay and offers to take his place. Back at Guido's house, the drunken and self-destructive Perce comes to and nearly tears his bandages off his head, forgetting about his recent injury. Roslyn puts him to bed. She then sits down with Gay. He asks her if a woman like her would ever want to have a child with him. She avoids the issue, and Gay goes to bed.
The next day, Gay, Guido and Perce prepare to go after the mustangs. Roslyn reluctantly tags along. After they catch a stallion and four mares, she screams that she hates the men when she learns that the mustangs will be sold for dog food. She then tells Gay she did not know she was falling in love with a killer. He tells her that he did things for her that he never did for any other woman, such as making the house a home and planting the garden.
She begs Gay to release the horses. He considers doing it, but when she offers to pay $200, it angers him. Guido tells Roslyn that he would let them go if she would leave Gay for him. She rebuffs him coldly. Perce also asks her if he wants him to set the horses free, but she declines because she thinks it would only start a fight. He frees the stallion anyway.
After Gay chases down and subdues the horse all by himself, he lets it go and says he just did not want anybody making up his mind for him. He and Roslyn drive off under the starry night sky. She tells him she would not mind having a baby as long as there was somebody there to make sure the child grew up into a human being.