The magic of all children has been released. Throughout the skies of Earth they swoop, crossing continents, changing shape, diving to the ocean depths and playing the deadly new spell-games. Rachel bides her time, watching the skies for what she knows will happen - the invasion of the Witches.

But when it comes it is not in the way anyone expects, and there is also a new enemy - the huge, terrifying Gridda-breed. To confront them will require all of Rachel's and her brother Eric's skill and courage, as they embark on a journey that takes them to Ool, home of the Witches - a world where mountains move and breathe, the sun never pierces the clouds and the snows are alive.