When thieves steal Larkspur, a prize thoroughbred brood mare, from the Conway ranch, her foal runs after her and is found by David Carey, an orphan who lives with his heartless aunt Hildegarde and uncle Thad. The lonely David befriends the colt, whom he names Sunset, and convinces his brutal uncle to let him keep the animal, arguing that they can reap a reward from selling the horse. While visiting the Conway ranch in search of advice about raising his horse, David is befriended by Jack Lenihan, the stablemaster, who offers the boy a job in exchange for special food for his colt. When Bill Conway and his daughter Wendy return to the ranch from the East, David realizes that Sunset is their missing foal. As David struggles with his conscience over returning the colt, his cruel uncle harnesses Sunset to a plow and beats the animal. To save the horse, Wendy offers to buy him and then realizes that he is Larkspur's missing colt. Wendy offers David a job as stableboy on the ranch, but David refuses out of guilt and decides to run away. He bids Sunset farewell, but the horse gallops after him and breaks a leg while trying to jump a fence. David begs the Conways to spare the injured horse and, to save Sunset's life, confesses that the animal is their missing horse. Touched by David's confession, Conway convinces the skeptical vet, Dr. Purdy, to use an experimental cast on the horse's broken leg, and after a shaky start, Sunset makes a miraculous recovery.

• List of films about horse racing

• Two Thoroughbreds at IMDb