Tensions between dwarfs and trolls are reaching breaking point in Ankh-Morpork, as both sides prepare to commemorate the ancient Battle of Koom Valley - which each side claims the other started. Vimes must solve a murder in the dwarf community while keeping the peace, reading Where's My Cow? to his son every night at six, and resisting the influence of a dark entity that feeds on old hatreds. A novel about how violence perpetuates itself, and how the cycle gets broken.