The Old Man on the Mountain is a fiction novel written for today's youth. Two young girls living in rural Nevada coerce their mom into "looking at a horse" destined for slaughter. She agrees to look at the horse, although she is mysteriously resistant. The horse turns out to look just like an old friend.

The story immediately delves into her childhood. Kate Walker is a very determined young girl who happens to crave horses. She plans, saves, and succeeds in her dream. She luckily finds the perfect horse, and her godmother and parents support her in her purchase and subsequent bonding with Rowdy. He is a bay gelding who is unwanted and also destined for the slaughterhouse when she finds him.

Tediously, she breaks him (or he breaks her), and they grow together. She spends several years grooming, riding, and competing on him. He is an incredible athlete. He takes her through many adventures, but he fails miserably as her dream barrel horse.

In her quest to learn barrels and gymkhana, she makes friends with the two best riders in the valley. They train, compete, and trail ride together. They find great solitude in a sacred area in the nearby mountains.

The story takes Kate and Rowdy to great fame and satisfaction. She and her friends make a great team.