The wee free men - Terry Pratchett

Up on the chalk downs they call The Wold, witches are banned - ever since the Baron's son vanished in the woods. Anyway, as all witches know, chalk's no good for magic. Nine-year-old Tiffany Aching thinks her Granny Aching - a wise shepherd - might have been a witch, but now Granny Aching is dead and it's up to Tiffany to work it all out when strange things begin happening: a fairy-tale monster in the stream, a headless horseman and, strangest of all, the tiny blue men in kilts, the Wee Free Men, who have come looking for the new 'hag'. These are the Nac Mac Feegles, the pictsies, who like nothing better than thievin', fightin' and drinkin'. Then Tiffany's young brother goes missing and Tiffany and the Wee Free Men must join forces to save him from the Queen of the Fairies-