This fantasy friendship between a child and a talking small animal begins when Wesley, a super-intelligent frog of a rare, invisible species, escapes from a research lab and turns up at orphaned, ten-year-old Marveline's window, begging water. Amazingly, she can understand his speech--but Wesley has previously had a similarly gifted friend, a boy, and so he knows she'll lose the ability when she turns eleven. Meanwhile, though, Wesley and the runaway Holly (Marveline's new name) have a fine time together as an act in a small traveling family circus, where tall gangling Holly fills out on the food and the love of the warm Italian circus family. This dream life comes to an end when the laboratory scientists Holly has defied and eluded finally track them down; but a nice uncle turns up to take her in, and--on the eve of her eleventh birthday--Wesley is smuggled by plane to find a mate and family of his kind in his native Central America. It's easy to call to mind comparable stories that outdistance this in wit or insight. This has the predictable appeal of the friendship, the circus life, and (less centrally) the research animal's view of the lab. It's okay, but uninspired, and consequently a little slack.