Volume 12 of the successful series. Penny and her friends are very excited: They get to participate in the Fit Dog show with their dogs Mailie and Dschastin. The competition includes hurdles, tunnels, a ball pit, and tasks where the dogs have to search for treats, fish for squeaky ducks, and swim. The first round goes quite well, aside from a few minor mishaps. But everything goes wrong in the second round, and it's not just Mailie and Dschastin who are struggling. Is someone manipulating the show? Fortunately, Penny and her friends are not only excellent dog trainers but also outstanding detectives.