After a hard year working on the stinking canals of Dunsgow, Fireboy's skill with steamboats has earned him barely half the money he needs to pay off his mother's bond. Only then can he reunite his family on the clean water of the River Slow. A chance meeting with a seer inspires him to trade in his boat for a new steam launch expressly designed for rivers, and to take on cargo for Baron Miner - the man who holds his mother's bond. If Fireboy has figured it right, the commission plus the money he's saved will free his mother in one trip.

What Fireboy can't figure in are the snags caused by Jake, a wily young juggler on the run from Baron Miner's men. By Lucide, half water sprite, trying to break free of her own bonds of duty. And by the binding lies of Karl Tinker, the Baron's mastermind in a campaign to destroy the source of magic on all the Five Rivers. Fireboy's journey takes him from the waters he knows to the tangled, bemagicked rapids of the highest reach of the land - to lose his new friends, his new boat, even even his own free will - unless he can discover which bonds really matter.