The Scary Monster Clean-Up Gang — Anne Margaret Lewis

The sly old swamp-witch, Gwrach y Rhibyn, meddles with a powerful new spell in the hopes it will make her Queen of the Wood. But it goes disastrously wrong. The whole town of Nant-y-Ceirw is trapped in the thrall of the hideous Shadow of Don't Care and the Bwganod of the Wood are in terrible danger. It's up to their human friends -- Gramps and David and Eleri and Eleri's Nan -- to rescue them. Somehow they must defeat the Shadow, but is it possible to fight magic?