Edward d'Eath, an Assassin and son of a down-and-out noble family, becomes convinced that the restoration of the Ankh-Morpork monarchy will solve the social change in the city which he blames for his family's humbling. He researches the history of the royal family and determines that Carrot Ironfoundersson is in fact the rightful heir to the throne.
Meanwhile, Captain Samuel Vimes, captain of the Ankh-Morpork City Watch, prepares for his imminent wedding to Sybil Ramkin, the richest woman in Ankh-Morpork. He also must deal with a new group of recruits that he has been required to take on for the sake of diversity: Cuddy (a dwarf), Detritus (a troll), and Angua (a werewolf—but Carrot is unaware of this, and believes she is included because she is female). When a string of seemingly random murders occur among the Guilds of the city, Lord Vetinari forbids Vimes to investigate in a successful ploy to ensure Vimes does investigate. Cuddy and Detritus are forced to work together, resulting in them becoming friends as they overcome their deep-seated racial enmity. Angua works with the talking dog Gaspode, and also forms a romantic connection with Carrot, who loses his virginity to her but handles the discovery that she is a werewolf poorly.
It turns out that d'Eath has stolen the gonne, the Disc's first and only handheld firearm, from the Assassins' Guild, with the intention of discrediting Vetinari's government through the murders. Any possessor of the gonne seems to become obsessed with the device. After d'Eath reveals his plan to Dr. Cruces, head of the Assassin's Guild, Cruces murders him and takes up the plan himself. The Watch prevents Cruces from killing Vetinari, but Cuddy and Angua are killed in the process. Vimes and Carrot confront and disarm Cruces, and Carrot helps Vimes resist the gonne's allure. Cruces gives Carrot the evidence that he is the royal heir, upon which Carrot kills Cruces with his sword and has both the evidence and the dismantled gonne buried with Cuddy. Angua gets shot 3 times by Cruces but since she is a werewolf she can only be killed with a silver weapon so is revived upon the moon's rising.
Vimes and Ramkin are married. Recent events have raised the Night Watch's profile, bringing a slew of new recruits. Carrot visits Vetinari, who is expecting Carrot to make personal demands as he is now in a strong position to blackmail the Patrician. What Carrot actually brings is a request for Vetinari to implement a plan for reforming the City Watch into an effective, integrated, comprehensive police force with better working conditions. Vetinari accedes, making Carrot Captain of the Watch and elevating Vimes to the recreated position Commander of the Watch, and the rank of Knight.
- En man på sin vakt (Swedish)
- Въоръжени мъже (Bulgarian)
- The title of the book is a double pun, both on the professional standards of the Watch (a man at arms being a professional warrior) and on the lack of actual men in the Night's Watch (only Vimes and Colon can be classified as men, as Corporal Carrot considers himself a dwarf, Constable Cuddy is a dwarf, Constable Detritus is a troll, Constable Angua is both a werewolf and female, the Librarian is an orangutan, and Corporal Nobbs was disqualified from the human race for shoving).
- Edward d'Eath's name is an obvious play on the word 'Death" but it is an old English name. The De'aths came over with William the Conqueror, and pronounce their name 'Dee-ath'. The old British TV series, "The Avengers" used the name for one of its villains,
- The iconograph box which has a brownie inside that paints pictures is a reference to Kodak's first mass-produced affordable camera which was called the "box brownie". A brownie is also the name of a helpful type of goblin.
- Twurp's Peerage is the directory of all the nobility of Ankh-Morpork and its satellites, describing their lineage and titles. It is a takeoff on Burke's Peerage. In colloquial English, "berk" and "twerp" are both pejorative names for an obnoxious, silly person. Berk was originally the cruder of the two deriving from the 1930s as a shortened version of Berkeley Hunt, the hunt based at Berkeley Castle, in Gloucestershire. In Cockney rhyming slang, hunt is a rhyme for cunt, giving the word its original slang meaning.
- When the Troll Detritus gets locked in the pork futures warehouse, he creates an elaborate "theory of everything" equation all over the walls, in an attempt to pass the time until he is rescued. He gets everything down to one final equal sign "=" before being rescued. Knowing Pratchett's frequent references to Douglas Adams' Hitch hiker's Guide to the Galaxy, it is pretty clear that the answer to the equation is 42 with Discworld having the Question, and the Hitch Hiker's having the answer.
- The dog pack leader, Big Fido's line that "all dogs are wolves" and the other dogs reactions to it, is particularly apropos because about the time the book came out, dogs were reclassified from the separate species canis familiaris to the subspecies canis lupus familiaris, making every dog a wolf - even a poodle.
- When Cuddy and Detrius are chasing Cruces down Grope Alley, Pratchett mentions that the origin of the name is "fortunately" lost in the mists of time. The original name of the street would have been Gropecunt lane which in Roundworld stems from the medieval era when street names reflected the occupations there. The name comes from Grope and Cunt (ie. a place where prostitutes practiced their trade). The earliest known use of the name is in about 1230 and the last one was in 1561. Streets with that name were often, not surprisingly, in the busiest parts of medieval towns and cities, and at least one appears to have been an important thoroughfare. Changes in attitude resulted in its replacement by more innocuous versions such as Grape Lane.
- The scene when Carrot nails the villain to a stone pillar with his sword, and then cleanly pulls the sword from the stone (and the villain's body) is a play on the King Arthur legend of drawing the sword Excalibur from the stone and clearly foreshadows that Carrot is really the king of Ankh-Morpork.