The book details the creation of Steam Trains and them coming into use. Moist Von Lipwig takes control of the new railway at the command of Lord Vetinari, working with Dick Simnel (the inventor of the steam train) and Harry King, employing many Goblins. Toward the end of the book, Moist works with Commander Sam Vimes to transport the Low King of the dwarves, Rhys Rhysson, to Überwald. The antagonists of the books are the traditionalist Grags who want to try and destroy the Clacks and the new railway.
The book was announced as Raising Taxes, during a tour for Making Money, but the name was later changed.