In every person's life there are difficult decisions. Moist von Lipwig, fraudster extraordinaire, master of art forgery and a true expert in forgeries, also faces a difficult choice: be hanged or turn the Ankh-Morpork Postal Service on its head. Having unsurely made a difficult, controversial decision, he must now ensure that, despite rain, snow, dogs, impassable roads, the Friendly and Benevolent Postal Workers Union, scrupulously honest and ethical competitors and midnight murders, the mail is nevertheless delivered on time purpose.