Elves are breaking through into Lancre, and they are nothing like the kind, wise beings of legend. Pratchett's elves are beautiful, cruel, and parasitic - they glamour their victims into adoration before tormenting them. The witches must defend Lancre against an invasion that most of the population actually welcomes. Magrat gets married, Granny Weatherwax faces her oldest rival, and the book makes a compelling case that iron is more useful than magic.