In a Neo-Victorian London of mechanical horses and aerial gondotrams, airship engineer Jasper Kendall Asher has a bright future ahead as the youngest member of the Engineers Order and a secret agent in Her Majesty's service. But a terrible accident brutally changes the course of his career, sending him instead to a dull life as a mechanic among the poor of St. Giles.

Three years later, unusual circumstances give him the opportunity to return into service as the main engineer for the Queen's new airship-and a chance to uncover the truth behind the unfortunate event that changed his life.

Along with an outlandish woman navigator, a reckless female agent, and his taciturn brother, Jasper resumes his work. From his workbench, to London's airharbour, to remote Scottish villages, he follows the trail of a scientific discovery that promises to reveal much darker plots than he initially imagined in his search for answers.