Abby Lovitt lives on a working ranch with her parents and nine horses. Jack is her horse. The family receives a note that asks if Mr. Lovitt had purchased a brown horse that had a foal the previous year. The horse was a thoroughbred and had disappeared from its owner’s stable. The brown mare in question could have been Jack’s mother, who died earlier, and the foal, Jack.
Abby likes another of the family’s horses, Black George. At a local training center, Abby puts Black George through many jumps. Sophia Rosebury, who is rumored to be an Olympic rider, trains at the same center. Abby rides Black George in a show, but the final day of the show is on Sunday, and Abby’s family believes that Sunday is for church. After many discussions, her parents decide that Abby can ride on Sunday. Because of that, Abby and Black George win the blue ribbon.
Abby’s family receives another note from the horse investigator. He tells how four pregnant horses were stolen. Two were found and had their foals. One was found but died shortly thereafter. Only Alabama Lady was still missing. The investigator wants to come to their ranch to look at Jack to see if he is the foal of Alabama Lady — this may be the horse Abby’s family called Pearl. Pearl died the previous year.
The next time Abby rides Black George at the training center, Black George clears a jump that is 4 feet high. When Abby learns how high the jump was, she grows scared and stops jumping. A few days later, she and her father return to the training center, but Abby refuses to jump anything high. Sophia quickly volunteers to ride Black George, and they easily take the high jumps.
Abby is jealous and now wants to do the jumps herself, but her father refuses. Only then does she realize that the whole point of her riding was to get Sophia interested in buying Black George. Abby’s father tells her that they don’t keep the good horses, like Black George, who is a diamond in the rough.
Soon after, Black George is sold to Sophia’s family for a very large sum of money, more than Abby’s family has ever received for a horse. The son of Alabama Lady’s owner visits. Jack is the foal they are looking for. Although this type of a horse could go for $20,000, the man agrees to sell Jack to Abby’s family for $5,000. Abby’s parents, after many discussions, decide to pay for the horse, but Abby won’t let them. She decides that her family has worked too hard to spend all their money on one questionable horse.
As it turns out, Abby made a good call. The “owner’s son” was a swindler. When the real owners of Alabama Lady show up, they tell Abby’s family that there is no possible way to track whether Jack is Alabama Lady’s offspring for certain. They intend to bring their situation before the Jockey Club for a decision. If the Jockey Club decides Jack isn’t the offspring, then the colt belongs to Abby. If they decide it is the offspring, then the real owners of Alabama Lady and Abby’s family would own Jack jointly. Abby’s family agrees with the compromise. No one knows if Jack is really Alabama Lady’s foal, but deep down, Abby believes he is a thoroughbred.