Steam is rising over Discworld, driven by Mister Simnel. He has produced a great clanging monster of a machine that harnesses the power of all of the elements, and it’s soon drawing astonished crowds. To the consternation of Ankh-Morpork’s formidable Patrician, Lord Vetinari, no one is in charge of this new invention. Who better to rectify this than the man he has already appointed master of the Post Office, the Mint and the Royal Bank: Moist von Lipwig.