Late summer, 1270. Although the Simon de Montfort rebellion is over, the smell of death still hangs over the land. In the small priory of Tyndal, the monks and nuns of the Order of Fontevraud long for a return to routine. Their hopes are dashed, however, when the young and inexperienced Eleanor of Wynethorpe is appointed their new prioress. Only a day after her arrival, a brutally murdered monk is found in the cloister gardens, and Brother Thomas, a young priest with a troubled past, arrives to bring her a more personal grief.

It is the autumn of 1278. The harvest is in. The air is crisp. Dusty summer breathes a last sigh before the dark seasons arrive. For Prioress Eleanor, dark times arrive early in Norfolk. The head of her order, Abbess Isabeau, has sent Father Etienne Davoir from their headquarters in France to inspect all aspects of Tyndal Priory, from its morals to its roofs. Surely the abbess would not have chosen her own brother for this rare and thorough investigation unless the cause was serious and she had reason to fear intervention from Rome.

Oxford, Spring 1353. When young bookseller Nicholas Elyot discovers the body of student William Farringdon floating in the river Cherwell, it looks like a drowning. Soon, however, Nicholas finds evidence of murder. Who could have wanted to kill this promising student? As Nicholas and his scholar friend Jordain try to unravel what lies behind William's death, they learn that he was innocently caught up in a criminal plot.

Hugh of Singleton, fourth son of a minor knight, has been educated as a clerk, usually a prelude to taking holy orders. However, feeling no certain calling despite a lively faith, he turns to the profession of surgeon, training in Paris and then hanging out his sign in Oxford. A local lord asks him to track the killer of a young woman whose bones have been found in the castle cesspit. She is identified as the impetuous missing daughter of a local blacksmith, and her young man, whom she had provoked very publicly, is in due course arrested and sentenced at the Oxford assizes.

The much-feared and hated Eudo - the Lord Bishop of Winchester's clerk - is bludgeoned to death in Pershore Abbey and laid before the altar in the attitude of a penitent. Everyone who had contact with him had reason to dislike him, but who had reason to kill him? The Sheriff of Worcestershire's thief taker, wily Serjeant Catchpoll, and his new and unwanted superior, Undersheriff Hugh Bradecote, have to find the answer. And as the walls of the abbey close in on the suspects, the killer strikes again....