It's happened again. Jill has planned a summer filled with her ponies and her friends, but something has happened. The Cortman Kids, Melly and Lindo, are coming to stay. For the summer. With their endless list of things they can do and Jill can't, like tennis. And they've come with their dogs. For the Cortmans are dog people, not horse people.

Jill has no choice but to make the best of it, and the Cortmans help out by deciding they'd like to learn to ride. They are then bought a stupendously beautiful pony called Blue Shadow. The Cortmans begin riding in shows, and that brings its own problems, but in the last show of all, Jill realises they are not as unsporting as she thinks.