As the book opens, a dwarf demagogue, Grag Hamcrusher, is apparently murdered. Ethnic tensions between Ankh-Morpork's troll and dwarf communities mount in the build-up to the anniversary of the Battle Of Koom Valley, an ancient battle where trolls and dwarfs seemingly ambushed each other. Lord Vetinari persuades Commander Vimes to interview a vampire applicant to the Ankh-Morpork City Watch. The new recruit, Lance-Constable Salacia "Sally" von Humpeding, along with Sergeant Angua and Captain Carrot, is attached to the investigation surrounding Hamcrusher's death.