Beaver Towers — Nigel Hinton

This is the first adventure in the "Beavor Towers" series. A magic spell whisks Philip away on his new kite to a far-off island where he meets the beavers - Mr Edgar and his grandson, Baby B. They tell him of the terrible danger that threatens them. The wicked witch Oyin has imprisoned most of the island's inhabitants in Beaver Towers, and when her powers are complete she will put them to death and rule the island. Philip has to get her spell book in order to save them.