Tono-Bungay is narrated by George Ponderevo, who is persuaded to help develop the business of selling Tono-Bungay, a patent medicine created by his uncle Edward. George devotes seven years to organising the production and manufacture of the product, even though he believes it is "a damned swindle". He then quits day-to-day involvement with the enterprise in favour of aeronautics, but he remains associated with his uncle, who becomes a financier of the first order and is on the verge of achieving social as well as economic dominance when his business empire collapses. George tries to rescue his uncle's failing finances by stealing quantities of a radioactive compound called "quap" from an island off the coast of West Africa, but the expedition is unsuccessful. George then engineers his uncle's escape from England in an experimental aircraft he has built, but the ruined entrepreneur turned financier catches pneumonia on the flight and dies in a village near Bordeaux, despite George's efforts to save him. The novel ends with George finding a new occupation: designing destroyers for the highest bidder.