The Madness of George III is set in London in 1788. King George has been on the throne for twenty-eight years; he and his beloved Queen Charlotte have fifteen children. William Pitt, a "Tory," a member of the political party that supports the King in particular and monarchy in general, is Prime Minister. His nemesis is Charles James Fox, who leads the Whigs, the party that seeks constantly to limit royal power. Pitt, Fox, and their supporters have been fighting each other for years before the play begins and will continue to do so for years after the twelve months or so portrayed in it are over.

George is still stinging from the loss of the American colonies in their War of Independence, which ended five years earlier.

The King has had mental and physical health problems off and on for some time. As evidence mounts that he is seriously ill—incessant ranting, and physical symptoms such as blue urine, among others—his monarchy begins to seem untenable. Pitt and the Tories fret about their loss of power, and everyone in Parliament jostles to be in the best position once the incapacity of the crown is established. George is eccentric, which makes it difficult to distinguish between mental illness and royal quirkiness. Pitt and Fox engage in an intense, high stakes Parliamentary battle over how and when the Crown's powers should be turned over the King's eldest son George, the Prince of Wales, who supports Fox.

The medical practices of the time border on the barbaric, and the King, whose condition worsens, is subjected to evermore horrible treatments. Just when the Parliament is about to vote for the Regency—in other words, for the Prince of Wales to be king in all but name—George III recovers, and his monarchy is saved, at least for the next decade or so.

Dramatis Personae