Set in the winter of 1372, in York, a man has drowned in the Ouse after a skirmish with some boys from St Peter's School. It soon becomes clear that his death was not an accident - he has been poisoned. But why would a humble pilot on the river be killed for possessing a young boy's purse? Suspicion falls on Father Nicholas Ferriby - Vicar of Weston and master of a small grammar school - who has already offended many with his unpopular beliefs. But is he really a murderer? One-eyed spy, Owen Archer, Captain of Archbishop Thoresby's guard and noted for solving many crimes, is quickly brought to the scene by his adoptive son, Jasper. Clear that the pilot has been killed for more than a purse, an increasingly cantankerous Thoresby reluctantly agrees to let Owen investigate the man's murder. Torn between solving the crime and looking after his wife, Lucy, who is expecting their long-awaited third child, Owen is soon taken away from home. When another man is found dead in the river and Owen and Jasper get nearer to the truth, they find their own lives in jeopardy...