hampstead heath is a wild area to the north of london. one october night, caleb and his sister blossom sneak out onto it hoping to get a clear view of a new comet but they are horrified when a stranger rises from the ground and tells them that they have been 'chosen'. beneath the heath is a land of powerful magic where lud, the king of the gods of the ancient britons, and brigantia, his queen, still rule. a terrible quarrel has broken out between them over the loss of lud's silver hand. unless the children find it before hallowe'en, autumn will never come and an endless summer will scorch the human world. meet the celtic gods and goddesses in all their terrible fiercesness and learn the real identity of jack frost. how can these brave and resourceful children ever hope to succeed against such magic?