Katelyn and her friend Gracie the Ghost, have decided that it is time to share their secrets with her brother Chase, exposing him to a whole new world when he discovers the secrets of Katelyn's much-loved horse, Princess Starr. After Katelyn and her horse compete at the County Fair, Princess Starr goes missing from her stable. After an unsuccessful search for her by the authorities, Katelyn, Gracie, and Chase must leave their real world to venture on their own into another dimension full of mystical creatures, where they are faced with the fight of a lifetime.