Koom Valley, where the trolls ambushed the dwarfs, or the dwarfs ambushed the trolls, was a long time ago.
But if he doesn't solve the murder of just one dwarf, Commander Sam Vimes of Ankh-Morpork City Watch is going to see it fought again, right outside his office.
With his beloved Watch crumbling around him and war-drums sounding, he must unravel every clue, outwit every assassin and brave any darkness to find the solution. And darkness is following him.
Oh . . . and at six o'clock every day, without fail, with no excuses, he must go home to read 'Where's My Cow?', with all the right farmyard noises, to his little boy.