About the book: 2021 / A petting zoo has opened in River Heights! Nancy, Bess and Georgie can't wait to go there and play with the adorable Shetland pony named Buttons. But it seems that Buttons himself does not want to meet visitors at all. Every night he mysteriously disappears from his pen and wanders around the city! Who produces Buttons? And why? Does anyone really want a pony to escape from the zoo forever? Young detectives will find out the truth!