Piper wants to ride in her first horse show, so she takes lessons from her dad's friend, Annie. Piper's horse keeps going lame, so Annie provides another one. Strange things are happening in Annie's barn and soon there are more questions than answers: Is Annie a criminal or an innocent victim? Who is threatening Annie and can Piper and the Horse Rescuers figure out a plan to help her? How does that horse keep getting out of his stall? And when will the river stop rising?