Marty is missing! When the Beacon Street Girls' beloved doggie mascot slips his collar and runs off, a nasty trick sends Avery, Charlotte, and Nick Montoya on a wild goose chase for the little dude. A heartbroken Charlotte wonders, have the Queens of Mean gone too far this time? Meanwhile, High Hopes Riding Stable, where Katani and Kelley have discovered a newfound passion for horses, needs a miracle to stay in business. Is Marty lost, kidnapped--or gone forever? Will Katani have to say good-bye to her favorite horse, the gentle, pretty Penelope?