Dangerous Fairies.A Magical Snow Globe.Discover the adventures of the Celtic Kids.Caitlin and Sean O'Brien see a strange ball of light. A fairy light called a Will o' the Wisp! But should they follow it? It could be a trick. And the fen is a dangerous place filled with patches of qickbog, tentacled bog-worms, and deadly goblin-fog. Plus Merdoc, the druid, is back. Can the twins trust him? Or does Merdoc have a new sinister plan?