Sir Richard Francis Burton is an explorer, linguist, scholar, and swordsman. His reputation has been tarnished, his career is in tatters, and his former partner is missing and probably dead. Algernon Charles Swinburne is an unsuccessful poet and follower of de Sade, for whom pain is pleasure and brandy is ruin. They stand at a crossroads in their lives, and are caught in the epicentre of an empire torn by conflicting forces: Engineers transform the landscape with bigger, faster, noisier, and dirtier technological wonders; Eugenicists develop specialist animals to provide unpaid labour; and Libertines oppose repressive laws and demand a society based on beauty and creativity, while the Rakes push the boundaries of human behaviour to the limits with magic, drugs, and anarchy.

The two men are sucked into the perilous depths of this moral and ethical vacuum, when Lord Palmerston commissions Burton to investigate assaults on young women committed by a weird apparition known as Spring Heeled Jack, and to find out why werewolves are terrorizing London's East End. Their investigations lead them to one of the defining events of the age, and the terrifying possibility that the world they inhabit shouldn’t exist at all.