On the last day of a summer vacation, Martin looks into a fox’s eyes, and discovers just what his Great Aunt Zavella meant when she warned him of the “little trick” that foxes can play. Suddenly, he has four legs and a bushy tail—and clever Sharpnose, who had engineered the whole encounter, is lodged in a boy’s body, with its oh-so-useful hands. Both are exhilarated by the switch, at least initially. Adding occasional freely sketched ink drawings that reflect the sunny tone, Gerstein crafts a tale rich in magic, music, and the profound pleasure of suddenly seeing the world through new eyes. Great Aunt Zavella, who grew up in the Old Country where “nothing is only one thing and everything can be anything”—and where every child learns fox language in the second grade—isn’t fooled for long; working subtle magic of her own with songs and good-humored persuasion, she soon has the pair happily back in their original bodies. New chapter-book readers will be won over by the episode’s engaging cast and well-tuned sense of wonder. (Fiction. 8-10)