As the book opens, a dwarven demagogue, Grag Hamcrusher, is apparently murdered, and the only witness is a confused Gutter Troll called Brick. As ethnic tensions between Ankh-Morpork's troll and dwarf communities mount in the buildup to the anniversary of the Battle Of Koom Valley, Lord Vetinari convinces Commander Vimes to interview a vampire applicant to the Watch. The new recruit, 51-year-old Salacia "Sally" von Humpeding, becomes, along with Angua and Carrot, attached to the investigation surrounding Hamcrusher's death.  Meanwhile, Nobbs and Colon begin an investigation into the theft of the fifty-foot painting The Battle of Koom Valley by the supposedly-insane artist Methodia Rascal from a city museum. Nobbs has a new girlfriend, the exotic dancer Tawneee (pronounced with each 'e' as a separate syllable); Nobby first caught her eye when slipping an IOU into her garter.  A recurring element in the book is Sam Vimes' race to get home every night by six o'clock to read the book Where's My Cow? to his infant son, no matter what; Pratchett uses this theme as a symbol of Vimes' determination never to compromise his own morality. Another is the game Thud, which first appeared in Going Postal; the game, which is a symbolic replication of the Battle of Koom Valley, requires the player to learn to think as both sides.  We learn more about the werewolf/vampire tensions, as Angua resists the urge to fight Sally over every tiny detail.