To the horror of Lord Vetinari's patricius, a new invention arrived in Ankh-Morpork - a huge clanging monstrous machine that uses the power of four elements - fire, water, air and land. Now the view of Ankh-Morpork is rather an image of an astonished crowd of people; some of them caught the spirit of the time and armed themselves with notebooks, and especially prudent ones with raincoats. Mockrist von Gubwig is not one of those people who like hard work . His intervention as chief of the Post Office, the Royal Bank and the Mint is of course vital... but largely depends on words that are fortunately weightless and need not be lubricated. Nevertheless, he likes to be alive, and therefore it is impossible to refuse Vetinari's offer. Above the Flat World rises a pair controlled by Mr. Simnel, a man in a flattened cap and with a counting ruler, who has made a very interesting arrangement with the sinuses and cosines. Mokrist will have to face grease, goblins, a thick controller who has the habit of bringing employees down the stairs, and several very evil gnomes. And if he stops, everything will go downhill...Translators: Mi Mi, Lyell Atani