Lisa Atwood's visitor, Merrill, loves horses almost as much as The Saddle Club does. Lisa, Stevie and Carole are happy to give Merrill a few pointers on her form over fences during their rides at Pine Hollow Stables.Then Merrill becomes convinced that she can only ride one horse. When The Saddle Club learns that she wants to take a Pine Hollow horse home to Maine, they know they have to do something. The girls have already planned a special surprise birthday party - a Yankee Swap - for Merrill. Will a Yankee Swap of another kind persuade Merrill that she can ride any horse well, or is one of The Saddle Club's beloved horses leaving Pine Hollow for good?.