Here there be dragons . . . and the denizens of Ankh-Morpork wish one huge firebreather would return from whence it came. Long believed extinct, a superb specimen of draco nobilis ("noble dragon" for those who don't understand italics) has appeared in Discworld's greatest city. Not only does this unwelcome visitor have a nasty habit of charbroiling everything in its path, in rather short order it is crowned King (it is a noble dragon, after all . . .).
Meanwhile, back at Unseen University, an ancient and long-forgotten volume-- The Summoning of Dragons--is missing from the Library's shelves. To the rescue come Captain Vimes, Constable Carrot, and the rest of the Night Watch who, along with other brave citizens, risk everything, including a good roasting, to dethrone the flying monarch and restore order to Ankh-Morpork (before it's burned to a crisp). A rare tale, well done as only Terry Pratchett can.