Marnie Clark of Curdie Vale can ride but she doesn't have a horse. She dreams of owning one and having the whole world to ride it in. Before too long Marnie is gifted Mrs Margaret 'Maggie' Whitlam, a beautiful, big Clydesdale—bold, fearless and able to jump anything.

From the very first ride, Marnie and Maggie get more adventure than they bargained for. Soon Marnie is learning to negotiate newfound friendships, pony club and how to stand up for what she believes in. Will her friendship with George Costa, another outsider, make being accepted harder? Or will being true to yourself be the hardest decision Marnie makes?