In the autumn of 1926, Ines Halloran, a widow and former schoolteacher, takes charge of the Perrin Lamb, a worn steam barge that carries the county's travelling library up the river Aure. She has a pilot who trusts the water more than people, an engineer who trusts nobody's repairs but her own, a cook, a fifteen-year-old clerk, and an inspector who has come to decide whether the service should survive another spring.

Then the river drops, the ledgers refuse to add up, and a fever reaches the villages at the top of the valley. The boat that was meant to lend books becomes the only thing that stays.

What the River Carried is a quiet, absorbing historical novel about reading, record-keeping and the people a county forgets to count.