Madison "Maddie" Martinez loves her weekly riding lessons, and she loves working with her favorite horse, Cloudy, every time. So she is shocked when she finds out Cloudy's former owners might want to buy her back! Maddie desperately concocts various plans to stop the sale: maybe she can raise money to buy Cloudy herself, or what if she can make the potential buyers lose interest? Maddie's online Pony Post friends--Brooke Rhodes, Hayley Duncan, Nina Peralt, who all share a love of Chincoteague ponies--can tell something is up, but at first Maddie is afraid to tell them what's happening. If she loses her only connection to Chincoteague, will they even want to be friends with her anymore?