The book unfolds through a series of loosely connected adventures experienced by Basil Grant, a former judge who suffered a dramatic breakdown and retreated to a Lambeth garret, and his more practical brother Rupert. Basil possesses a mystical perspective on life, seeing hidden truths where others see only cold facts. Through various encounters, the protagonists stumble upon the Club of Queer Trades, an eccentric Bohemian society whose membership requires inventing an entirely new, legal method of earning a living.
The stories introduce a succession of bizarre figures and trades. Major Brown is plunged into a surreal mystery involving yellow pansies spelling out a death threat and a hidden coal-cellar. Another episode exposes the Great Organizer of Repartee, a man who hires himself out to be insulted at dinner parties so his clients can shine. Later tales involve a vicar trapped into impersonating an old woman for a criminal enterprise, an arboreal real estate agent who deals exclusively in tree-top houses, and a professor whose sudden mastery of a new language causes him to dance continuously.
Throughout these episodes, Rupert acts as an amateur detective, eagerly leaping to cynical conclusions, while Basil solves mysteries through spiritual atmospheres and intuitive leaps. The narrative constantly subverts conventional detective fiction tropes. Instead of solving grim murders, the characters navigate elaborate practical jokes, sophisticated hoaxes, and novel commercial enterprises born of modern boredom.
As the accounts accumulate, they reveal a subterranean network of imaginative businesses designed to inject romance and wonder into an increasingly standardized civilization. The stories suggest that the modern world suffers not from a lack of facts, but from a deficiency of poetry and play. The overarching journey culminates in the discovery of the club's inner sanctum, where Basil presides over these joyful anomalies as a judge of human absurdity.
