To the horror of Lord Vetinari, Patrician of Ankh-Morpork, a new invention has arrived in the city — a huge clanking monstrous machine that harnesses the power of the four elements: fire, water, air, and earth. Now the face of Ankh-Morpork is more like a picture of a stunned crowd; some have caught the spirit of the age and armed themselves with notebooks, while the especially foresighted have taken raincoats.
Moist von Lipwig is not one of those people who enjoy hard work. His interventions as head of the Post Office, the Royal Bank, and the Mint are, of course, of vital importance… but they depend largely on words, which fortunately have no weight and need no lubrication. Nevertheless, he likes being alive, and so Vetinari’s offer is impossible to refuse.
Steam is rising over Discworld, driven by Mr. Simnel, a man in a flattened cap with a slide rule, who has made a very interesting arrangement with sines and cosines. Moist will have to deal with grease, goblins, a stout controller with a habit of throwing employees down the stairs, and several very angry dwarfs. And if he stops, everything will go off the rails…