Warning! Spoilers follow
The story begins with the sale of a golem, under suspicious circumstances; and continues with the death of a priest, Father Tubelcek, and the Watch's subsequent investigation, lead by new recruit, Cheery Littlebottom, a dwarf alchemist hired for a new forensics department, who discovers that the last person seen by the priest was a golem, by enlarging an image of the priests eye, and finds a piece of paper in his mouth, similar to the chem used to give life to a golem.
Commander Vimes, after thwarting an assination attempt on himself, must keep an appointment with the Royal College of Heralds. After a brief education in heraldry by the chief herald, the vampire Dragon, he is informed that he cannot have a family crest, as one exists, but was withdrawn after Vimes' ancestor killed a king. He is also told that Corporal Nobbs is an Earl.
Later, the proprietor of the Dwarf Bread Museum is found dead, and the Patrician is found poisoned. Dorfl, a golem, tries to turn himself in for the murder, but Carrot believes Dorfl was trying to bring the priest back to life the only way he knew how.
Later, despite a constant watch, the Patrician is poisoned again, while across the city golems are committing suicide, leaving messages which include the phrase "clay of my clay". Commander Vimes tracks down Mildred Easy, the only member of the Patrician's staff who can't be located, and finds her at her at a funeral for her grandmother and baby brother, both poisoned in the same way as the Patrician.
Carrot suspects that the golems have created a new golem to be their king, with the help of the priest to provide it's chem, and using the oven in the Dwarf Bread museum, but were ashamed when it started to kill people. Carrot and Angua follow Dorfl, to find him mobbed by a crowd, which Carrot disperses, before arranging to buy Dorfl from his owner. Carrot then places the deed of ownership inside Dorfl's head, alongside his chem, which causes the golem some difficulty. As this happens, Fred Colon, who had been questioning golem owners, wakes to find himself tied up and escapes with the help of Wee Mad Arthur, a gnome rat hunter the Watch encountered while investigating a case of poisoned rats in a dwarf café. Meanwhile, Commander Vimes, stressed over his inability to find how the Patrician is being poisoned, discovers a bottle of whiskey in his desk drawer.
Fred and Wee Mad Arthur are chased by the king golem, and manage to escape. The king falls a great height and is smashed on the ground, but Fred is amazed when the golem starts to piece itself back together. Vimes is visited by the heads of the Guilds, who have been told to search his desk. They are overpowered by the smell of whiskey, and see Vimes slumped over his desk. They find a packet of powder in the desk, but Vimes eats the contents. He knew the whiskey was planted in his desk so that he would be tempted, and swapped the arsenic planted there for a packet of sugar. He then realises how the Patrician is being poisoned; he goes to the palace to question Miss Easy, and finds that the candles used in the Patricians chambers are not used anywhere else; and that Miss Easy had taken the stumps to her grandmother.
Carrot, Angua and Cheery go to the candle factory, after making thir way through streets full of animals - Dorfl has determined that no one should have a master, and find the king golem. Dorfl faces the king, and eventually beats him, but is almost destroyed in the process. Vimes orders that he be taken away to be repaired, and given a tongue. Vimes then goes to face Dragon, who had been behind the plot. Dragon had long been preoccupied with preserving the royal lineage in Ankh-Morpork, and upon discovering evidence that Carrot is the heir, and horrified by his relationship with Angua, a werewolf, Dragon tried to get the Patrician out of the way, and install a fake, easily controlled, royal - Nobby - as ruler of the city. The solution had only occurred to Vimes after he found the whiskey and arsenic - only a vampire could have flown through his window, and remembered his visit to the College of Heraldry, where Dragon had pointed out the Candlemaker's crest in particular, and shown his the poisson, both a heraldic symbol for a lamp, and a blatantly placed clue.
The book ends with Dorfl joining the Watch.Synopsis