"Why couldn't you just leave me alone?" When Thoroughbred trainer Monty Everett suddenly needed a pony boy who might double as an extra rider, Dame Fortune smiles on him with the appearance of MacLean Cardy. But when asked if he would gallop race horses as well, the boy tells Monty in no uncertain terms...never Julie Jefferson, Monty's fiance' and owner of the champion mare, Sunbonnet, likes Mac immediately but believes that she has seen him somewhere before. Proving to be exceptionally competent with the horses, Mac unknowingly slides into the role of mentor to young, Brad Russell, an aspiring jockey. Watching Mac coach Brad reinforced Julie's belief that he could be or had been a rider, making her even more determined to find out why he so adamantly refused to ride. With Sunbonnet's rider injured in an accident, Julie's relentless pursuit of Mac's identity brings her to confront Mac and ask him for the impossible.