It is 1889, and Paris is on the cusp of industry and power. The Exposition Universelle has breathed new life into the streets and dredged up ancient secrets. No one keeps tabs on dark truths better than treasure-hunter and wealthy hotelier Séverin Montagnet-Alarie. When the elite, ever-powerful Order of Babel coerces him to help them on a mission, Séverin is offered a treasure he never imagined: his true inheritance.

To hunt down the ancient artifact the Order seeks, Séverin calls upon a band of unlikely experts: an engineer with a debt to pay, a historian banished from his home, a dancer with a sinister past, and a brother in arms if not blood. Together, they explore the dark, glittering heart of Paris. What they find might change the course of history—but only if they can stay alive.