A sister searches for her missing brother as a new power rises amid the splendour and the squalor of a once great city in this steampunk fantasy epic.

Lower Rhumbsford is a city far removed from its glory days. On the banks of the great River Rhumb, its founding fathers channelled the river's mighty flow into a subterranean labyrinth of pipes, valves and sluices, a feat of hydraulic prowess that would come to power an empire. But a thousand years have passed since then, and something is wrong: the pipes are leaking, the valves stuck, the sluices silted, and the once-torrential Rhumb has been reduced to a sluggish trickle.

The fortunes of the Locke family, descendants of the city's most celebrated engineer, are similarly reduced. In a once-fashionable quarter of the once-great city, siblings Samuel and Briony Locke are about to be drawn into a web of ancestral secrets and imperial intrigues, as a ruthless new power arises...