Katherine "Katy" McLaughlin has dreams of running her father's Wyoming horse ranch, but her father, Rob, has other plans. He is grooming her older brother, Howard, to take over the ranch and sends Katy away to a private school where she feels like a misfit. Rob is having trouble understanding his daughter as she continually defies his authority to follow her own path. When she comes home for the summer, Katy is met with her father's disapproval because she did not finish a writing assignment at school, but is greeted by her mother, Nell, and Howard. Howard wants to attend college. While out riding, Katy finds a black wild mustang, and feels a connection with the horse. She sets off to tame "" (Swedish for little girl), despite her father's protests.