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.

The Monastery at Whitby is ruled over by the powerful and independent Abbess Hild. But when she needs someone to confide in, she turns to the honest warmth of her friend Fridgyth, the half-pagan herb-wife. A divisive and life-altering decision taken at the Great Synod is swiftly overshadowed as the monastery is ravaged by a deadly plague. As she tends the sick, Fridgyth starts to suspect that not all the deaths are natural. Despite Hild's stern warnings "not to meddle" she sets out to investigate.

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.

In the fair autumn of Our Lord's grace 1431, the nuns of England's St. Frideswide's prepare for the simply ceremonies in which the saintly novice Thomasine will take her holy vows. But their quiet lives of beauty and prayer are thrown into chaos by the merciless arrival of Lady Ermentrude Fenner and her retinue of lusty men, sinful women, and baying hounds. The hard-drinking dowager even keeps a pet monkey for her amusement. She demands wine, a feast.... And her niece, the angelic Thomasine.