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

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. The erstwhile mighty Rhumb is sluggish and about to freeze over for the first time in memory.

In a once fashionable quarter of the once great city, in the once grand ancestral home of a family once wealthy and well-known, live the last descendants of the city's most distinguished engineer, siblings Samuel and Briony Locke.

Having abandoned his programme in hydraulic engineering, Samuel Locke tends to his vast lock collection, while his sister, Briony, distracts herself from the prospect of marriage to a rich old man with her alchemical experiments. One night, Sam leaves the house carrying five of his most precious locks and doesn't come back...

As she searches for her brother, Briony will be drawn into a web of ancestral secrets and imperial intrigues as a ruthless new power arises. If brother and sister are to be reunited, they will need the help of a tight-lipped house spirit, a convict gang, a club of antiques enthusiasts, a tribe of troglodytes, the Ladies Whist Club, the deep state, a traveling theatrical troupe and a lovesick mouse.

Epic, rollicking and in love with language, Jacob and Sara Emery's sprawling debut novel of humble kitchen magics and awe-inspiring civil engineering is a rare and delicious commodity - the world's first hydropunk novel.