- Gabrielle Anwar as Sonora Webster
- Michael Schoeffling as Al Carver
- Cliff Robertson as Doc Carver
- Dylan Kussman as Clifford
- Kathleen York as Marie
- Frank Renzulli as Mr. Slater
Sonora Webster is a stubborn orphan who lives with her aunt during the Depression. She has a love of horses, and one day before school, loses a bet that hers can jump a fence. It breaks and the cows get out, forcing her to be late. After she is given detention, her aunt tells her that because of her behavior and the family's financial difficulties, she is going to be put into an orphanage. Instead, she slips out of the house during the night.
Sonora ends up at a county fair and sees Marie perform as a diving girl. A diving girl jumps onto a horse as it runs up a steep platform just before it leaps off into a pool of water. She then informs Doc Carver that she is his new diving girl. He informs her that she is too young, her body isn't developed enough, and tells her she should go back home. She stubbornly twists her arms and legs around a chair to show him she won't leave until he gives her the job. Instead, he just places her and the chair outside of his tent.
Ending up in the stable with the horses, Doc sees how talented Sonora is with them and decides to give her a job as a stablehand. She then begins traveling with them, bonding with his son Al and even Doc himself. Al wins a wild horse in a game of cards, and he says that if she can tame it, he believes his father will give her a chance to train as a diving girl. She surprises him one day by riding up on it and he promises she can train to be a diving girl if she can mount it while it's moving. After multiple attempts, she finally succeeds and Doc keeps his promise, much to the chagrin of Marie. She and the wild horse, Lightning, develop a special bond which proves important later in the film.
One day, Marie falls and dislocates her shoulder, leaving her unable to perform. Thus, Sonora becomes the diving girl, even though the swimsuits don't fit her. Although she has never actually dove with Lightning into the pool of water, Sonora is successful at her first jump. Marie is so jealous that she makes unreasonable demands of Doc to ensure her stardom status, and after he refuses, she quits the show rather than share billing with Sonora.
Al and his father have always had a difficult relationship, which isn't helped by his burgeoning romance with Sonora, and one day he leaves after having a particularly bad fight with him. He and Sonora have almost shared their first kiss, and he promises to write her. Again, he keeps his promise, but Doc, protective of her, hides his letters from her. He and the new stablehand Clifford (who she met earlier) leave the farm in search of work, and that night Lightning falls ill. Sonora spends the night worrying over him and is awakened by Al, who has returned and discovers that Lightning ate some moldy hay and has developed colic. They work together to heal him and are walking him when Doc and Clifford return, telling them that the show is over as there is no more work to be had.
Al asks Sonora why she never wrote him, and she tells him that she never received any letters. They are both confused over the missing letters, but put it behind them. It is then learned that he got a deal with the Steel Pier in Atlantic City to perform the show. This seems to patch up old differences, and just as everyone seems to be getting along, Doc passes away en route to there, apparently from a heart attack. Now Al takes over his father's role as a presenter. On his first day, he is extremely nervous, so Sonora finds Doc's famous fringed jacket to give him confidence. When she finds it, she also finds one of his old letters, confessing his love for her. When she finds him, she lets him know she feels the same.
Meanwhile, Clifford has acquired a rusted-out motorcycle from a friend in Atlantic City and plans to refurbish it to working status; Sonora is unimpressed and laughs at the notion.
Al and Sonora perform at Atlantic City in front of their largest audience. Everyone is nervous and excited. As she is climbing the ladder, he proposes to her. She accepts and gets ready to do the jump. The horse, a jittery stallion who is not her usual partner Lightning, is anxious because of all the noise from the band and the crowd, and just before the jump a cymbal crashes loudly, which causes him to falter and trip. Sonora keeps her eyes open as they fall into the water. Both of them make it, but her vision is impaired, yet she hides this from Al and won't seek medical attention for the condition.
The next day when she wakes up, Sonora discovers she can't see. The doctor diagnoses detached retinas in both her eyes due to uncontrolled hemorrhaging behind them (a result of the high impact of the dive and her open eyes at the point of it) and tells her the condition is permanent and she will be blind for the rest of her life. In order to avoid a breach of contract lawsuit, Al must find another diving girl within a week, and calls Marie, who returns to be it.
Clifford has been working on his "new" motorcycle and gets it back in working condition. He demonstrates his new act for a small crowd including Al and Sonora—it is an enormous metal ball in which he rides around inside on the motorcycle, doing loop after loop. The crowd is amazed and he is pleased with his new "death-defying" act.
Meanwhile, Sonora misses diving terribly, and feels utterly helpless and like a burden to Al. She tells him of her desires to dive again, and indicates her unique bond with Lightning as evidence that she could do it again as she knows him so well. She and Al work together to try to train her to mount him again, much the same way she and Doc once worked together earlier to train her to do so in motion. She is stubborn and refuses to give up, but Al forces her to accept the fact that it is impossible. She spends some quiet time with Lightning that night.
The next day, with the help of Clifford, Marie is locked in her dressing room, and Sonora climbs the platform. Though Al is scared for her and shouts at her to come back down, the crowd doesn't know she's blind, and she uses her other senses to have a very successful jump. She is again the diving girl, and her voice-over tells us that she continued diving for 11 more years. She and Al get married and live happily ever after.