When Lisa, Carole and Stevie head west to the Bar None Ranch, they have a great time planning a Halloween party with their friends Kate and John, a Native American boy who works on the ranch. The Saddle Club is also thrilled when they get the chance to see a herd of wild horses, including the beautiful grey stallion that Kate wants to adopt. Then John tells the girls a mysterious Indian legend about a grey stallion, and warns Kate to keep her distance from the one in the herd. Is John just playing a Halloween trick or is Kate about to ride into danger? The Saddle Club is about to find out!