Modest and unassuming theology student Paul Pennyfeather falls victim to the drunken antics of the Bollinger Club and is subsequently expelled from Oxford for running through the grounds of Scone College without his trousers. Having thereby defaulted on the conditions of his inheritance, he is forced to take a job teaching at an obscure public school in Wales called Llanabba, run by Dr Fagan. Attracted to the wealthy mother of one of his pupils, Pennyfeather becomes private tutor to her boy, Peter, and then engaged to be married to her—the Honourable Mrs Margot Beste-Chetwynde (who later becomes "Lady Metroland," and appears in Waugh's other novels).[5] Pennyfeather, however, is unaware that the source of her income is a number of high-class brothels in South America. Arrested on the morning of the wedding, after running an errand for Margot related to her business, Pennyfeather takes the fall to protect his fiancée's honour and is sentenced to seven years in prison for traffic in prostitution. Margot marries another man with government ties and he arranges for Paul to fake his own death and escape. In the end he returns to where he started at Scone. He studies under his own name, having convinced the college that he is the distant cousin of the Paul Pennyfeather who was sent down previously. The novel ends as it started, with Paul sitting in his room listening to the distant shouts of the Bollinger Club.
The novel was dramatised as the 1969 film, Decline and Fall... of a Birdwatcher starring Robin Phillips and also by Jeremy Front in a 2008 BBC Radio 4 production starring Alistair McGowan as Pennyfeather, Jim Broadbent as Grimes, Andrew Sachs as Prendergast, Edward Hardwicke as Dr. Fagan, Jonathan Kidd as Philbrick, Joanna David as Margot Beste-Chetwynde, Emma Fielding as Flossie, and Richard Pearce as Peter.