Henry believes in trolls and magic, unlike his sensible sister Lucy and his dad who knows twenty-six reason why trolls don't exist. But Henry is right, there is magic in the wood behind their garden, magic that can turn evil when the moon is blue. Once in a blue moon anything can happen and now the moon is blue, magic is taking over and and Henry's dad gets turned into a pelican with the tail of a fox for going around saying that he knows twenty-six reasons why trolls don't exist.