Dedication. They may be called the Palace Guard, The City Guard or the Patrol. Whatever the name, their purpose in any work of herioc fantasy is identical: it is, round about Chapter Three, (or ten minutes into the film) to rush into the room, attack the hero one at a time, and be slaughtered. No one ever asks them if they wanted to. This book is dedicated to these fine men. After putting this on the frontispiece, with his tongue of course firmly in his cheek, the author proceeds to give these faceless men feelings, hang ups . . . and faces.

The Night Watch is down to just three men - Captain Vimes, Sergeant Colon and Corporal Nobbs.  Colon and Nobby spend most of their time guarding gates and streets and bridges against nothing much; guards just add that extra special touch to public buildings.  Vimes spends most of his time in a hazy drunken state to escape the depressing realities of his job. The criminals are in the ascendant, the Thieves's Guild and the Assassins practically help to run the city, and the Watch is a caricature of itself.  It has taken years to achieve this status quo, and Vetinari is rather proud of the hard-won equilibrium that the city has reached.

Well, it appears there is a conspiracy to bring back the king of Ankh-Morpork. Secret society, magical book stolen, summoning of monsters to terrorise city, etc. Nasty stuff, but then, plots often are. No plot, no plot, as it were.

    The Librarian knuckled his way urgently along the dark aisles between slumbering bookshelves.
[.....]
    As an ape, he had no doubts whatsoever about his eyes and believed them all the time.
Right now he wanted to concentrate them urgently on a book that might hold a clue. It was in a section no one bothered with much these days; the books in there were not really magical. Dust lay accusingly on the floor.
    Dust with footprints in it.
    "Oook?" said the Librarian, in the warm gloom.
    He proceeded cautiously now, realising with a sense of inevitability that the footprints seemed to have the same destination in mind that he did.

    He turned a corner and there it was.
    The section.
    The bookcase.
    The shelf.
    The gap.
    There are many horrible sights in the multiverse. Somehow, though, to a soul attuned to the subtle rhythms of the Library, there are few worse sights than a hole where a book should be.
    Someone had stolen a book.

But far away in the Ramtops, the inhabitants of a small dwarf mine are having problems of their own, involving the red-haired cuckoo in their collective nest. Six foot seven and built like a tank, Carrot is the biggest 'dwarf' there ever has been, ever. He was adopted by the dwarves one winter when he was found as a toddler near some burned-out wagons and dead bodies. His parents never got around to finding next of kin... probably because he didn't have any (bandits being something of an institution in some parts of the Ramtops). But Carrot has grown up to be a bit of a problem... his father, the king of the mine ('king' meaning a sort of senior engineer), decides that Carrot must return to his own kind for the sake of everyone's peace of mind. And so Carrot Ironfoundersson sets off to join the Venerable Order of Watchmen of the Cities of Ankh and Morpork.

    "There used to be some old prophecy or something," said Brother Plasterer. " 'Yea, the king will come bringing Law and Justice, and know nothing but the Truth, and Protect and Serve the People with his Sword.' You don't have to look at me like that, I didn't make it up."

Carrot is a sort of human quantum butterfly; his smallest actions cause huge storms in all sorts of places. He's called "Carrot" not because his hair is orange, but because he's carrot-shaped: the hugely muscled shoulders and massive arms taper down past tree-trunk thighs to equally well-built legs. After a life-time spent working on his knees and banging his head on ceilings, the long journey to Ankh-Morpork in the fresh air suits him. It puts a final polish on his muscles and gives him time to learn the whole book of laws and ordinances he was given back home, along with a very old, notched, un-magical sword and the Protective (for all that hand-to-hand fighting on rooftops, etc).

    "Well, I don't know about any Sec'y," said the guard. "You want Captain Vimes of the Night Watch."
    "And where is he based?" said Carrot, politely.
    "At this time of day I'd try the Bunch of Grapes in Easy Street," said the guard. The guard gave him what could loosely be called an old-fashioned look. It was practically neolithic.
    "What was it you done?" he said.
    "I'm sorry?" said Carrot.
    "You must of done something," said the guard.
    "My father wrote a letter," said Carrot proudly. "I've been volunteered."
    "Bloody hellfire," said the guard.

But Carrot is to be disappointed; Ankh-Morpork is full of thieves! (And murderers! And dwarves misbehaving in bars! Anarchy!) But here is someone whose earnest desire To See Justice Prevail, To Uphold The Law and Serve The People, is suddenly let loose on a very comfortably corrupt society. And with all the good will and anxious honesty in the world, Carrot goes on to set the city on its head. Before he can really get started, however, a larger quantum animal appears in Ankh-Morpork. Huge, scaly, stinking and no longer extinct, a draco nobilis is wreaking bizarrely controlled havoc in the city. Vimes is outraged, but totally helpless. Is it a case of a real dragon? Is it wizardry? Is there some sort of secret conspiracy?

Unless the Watch can find a solution, there won't be much city left - and so with the help of an eccentric, aristocratic, middle-aged dragon-breeder (draco vulgaris, of course), Sergeant Colon's archery skills, Carrot's earnest happy face, and Nobby lurking in the background exclaiming "Cor!" at odd moments and stealing the tea money, the Watch sets out to slay a dragon, whilst trying to avoid everyone else who's doing same (and they only care about the treasure hoard). It wouldn't be a Discworld book without Cut-me-own-throat Dibbler trying to sell 'helpful' things like anti-flame ointment (guaranteed or your money back if it doesn't protect you from white-hot dragon fire...) and a cloak of invisibility, also guaranteed - look in this mirror and see if it doesn't work. "Well of course you can't see any glass, its invisible, innit?"