When Wonder is about to start training for the important breeder's Cup Race, Wonder's regular jockey is injured and can't ride. Because Wonder won't perform for any other jockey, Ashleigh is called upon to ride in the race.

After disease wipes out her family's breeding farm, Ashleigh determines she will never care for a horse again until a small, sickly foal is born at the new farm that her family manages.

Ashleigh Griffen's horse, Wonder, gets a new trainer, who is very harsh and says that Wonder is untrainable, and Ashleigh worries and contemplates giving up on Wonder when he begins to behave erratically.

On a hike, Tracy Jordan and her brother find a mustang who is hurt. They nurse him back to health, but find that their father doesn't want them to have the horse. When he treatens to "get rid of it," Tracy must find the courage to set the mustang free.

After the loss of her horse, Lightening, Ashleigh's dreams of becoming a jockey crumble and loneliness sets in, but when her best friend Mona gets a horse of her own, Ashleigh wonders if she will ever find a horse that compares with Lightening.

Samantha McLean is ecstatic over finally owning her own horse and sets out to turn Shining, Wonder's difficult and neglected half-sister, into a winner, but then the parents of a little girl who cannot walk offer to buy Shining.

Twenty-three-year-old Ashleigh finds her childhood diary and relives her experiences with Stardust, her first horse, which include an encounter with horse thieves and a fight against a deadly virus that swept through the family stables when she was eleven.