On Midsummer Night, dreams are especially powerful. So powerful, in fact, that they can cause the walls between realities to come crashing down. And some things you really don't want to break through.

The witches Granny Weatherwax, Nanny Ogg and Magrat Garlick return home to discover that elves have invaded Lancre. And even in a world of wizards, trolls, dwarfs, Morris dancers - and the odd orangutan - they're spectacularly nasty creatures.

The fairies are back - and this time they don't just want your teeth...