Alison can`t believe it when her mother sells her beloved horse Duchess right out from under her. Full of spite, she joins her cousin Becky and friend Meg for a trip to Wyoming to meet eccentric Aunt Terri-Lyn. Homesick for Mustang Mountain Ranch, Becky is thrilled to meet her mother Laurie in Wyoming. Horse-crazy Meg can`t wait to catch a glimpse of some wild horses on Terri-Lyn`s remote prairie spread. The girls even have a chance to attend a wild horse auction. But if Alison can`t curb her reckless actions, it might just ruin the summer for everyone.