There is a new girl, Cassidy, at Storm Cliff, and she seems out of place at a riding stable because she knows nothing about horses and is even a little afraid of them--so Ryleigh sets out to solve the mystery of just who Cassidy is and what she is doing at the camp.

Twelve-year-old CeCe Monroe is enrolled at Storm Cliff Stables as Cassidy because she does not want the other girls to know that she is an actress, so when Aunt Jane asks her to assist with the movie that is to be filmed at the stables she is mostly afraid of blowing her cover--but when she realizes that the movie man calling himself Paul Martino is not the man she knows, she finds herself cast in the role of detective.