Jay Barton has spent her life on the outside, being overlooked and mocked for her tomboy ways. All she wants to do is ride her favourite pony, which belongs to her much wealthier cousin. But then Jay shows a talent for winning the illegal pony races her uncle takes her to, and he starts to push her to take more and more risks. At 15, Jay decides to run away, to live the life of a stable hand.

Her fortunes are changed when she meets Manhattan: a pedigree grey racehorse who has used up all her chances and is now neglected and despised. Jay recognises a fellow misfit. She fights to give Manhattan one last opportunity to show she is the champion she was born to be. Together, they face a world of prejudice and cruelty and fight back the only way they know by becoming the best.