It is the spring following the events in Otto and the Flying Twins, and Otto's world is still strangely unpredictable: the Karmidee still an underclass of 'magicos', his parents at odds, and the twins still unable to fly free. And the City of Trees is in the grip of something strange - with the approach of spring, when there should be warmer weather, carnivals and celebration, there is instead increasing cold, snow, bitter blizzards, a frightening upside-down world of ice. Once again, the Karmidee are blamed. But if they ever knew how to control the weather, they have long ago forgotten. Otto and Mab must help to find the answer. Otto encounters the legendary Wool Bandits, helps a miniature family with a dangerous secret and, together with new and extraordinary friends, must challenge the ancient powers of the sinister Bird Charmers.