Although Schwab’s novel is a work of fantasy that takes place across parallel worlds, her work borrows from reality because each of the settings is a reimagination of London. The story takes place in October 1819, and Grey London is patterned after the city during this period. By 1815, London was the largest metropolis in the world with a population exceeding 1 million. This booming population was assisted both by bustling migration from other parts of Great Britain and by falling child and adult mortality rates thanks to improvements in sanitation. London lies in the southeast of England and occupies both sides of the River Thames. The river is 205 miles long, beginning in the Cotswold Hills in the south of England and winding east toward London and the North Sea on a “pastoral and undramatic” course (“River Thames,” Encyclopedia Britannica, 30 May 2023).

The Thames flows past many famous structures, including Windsor Castle in Berkshire, Westminster Abbey, and St. James’s Palace. As a frequent guest of and messenger to England’s royalty in Grey London, the novel’s protagonist, Kell Maresh, is well-acquainted with these regal locales. As Kell travels through Grey London, he sees or visits familiar, real-life landmarks, such as when he delivers a message to King George III at Windsor Castle in Chapter 1.