Lady Margaret of Ashford is a healer with the gift of sight - a dangerous combination in the England of 1632 - but she keeps a low profile as the widowed mother of two growing girls and a four-year-old son by her second husband, Gilbert de Vilers, a former monk.
A resourceful woman, Margaret maintains her London home with economy and comfort, living quietly, exhausted by the recent excitement of former days when Gilbert was held for ransom in France and Margaret had to use her wits and the aid of friends to gain his release.
This latest adventure occurs closer to home Margaretís security is threatened by a father-in-law with great ambitions and a penchant for getting involved in disputes over the title to the lands of his estates at Brokesford Manor, the family legacy. Most important is a grove of trees that contains a mysterious spring wherein, as local folklore would have it, dwells an evil water spirit who requires the frequent sacrifices from the locals.
Driven by pagan rituals and native superstitions, the villagers are oblivious to the looming dangers of the Inquisition, but Margaret is all too familiar with the power of the Church. She seeks a resolution to the Sieur de Vilers legal problems without having to mortgage her home in the process, nor the future of one of her marriageable daughters. To that end, Lady Margaret introduces Huber de Vilers to an alchemist, Brother Malachi.
Brother Malachi creates an impressive forgery of an ancient deed that will hopefully sway the magistrate in the de Vilersí favor. But to plant the evidence, Gilbertís family must visit Brokesford Manor, where they encounter all means of trouble, not the least of which is the increasingly erratic and paranoid Lady Petronilla.
Convinced she is with child, Petronilla, the wife of Gilbertís older brother, Hugo, has a violent aversion to Margaret, jealous of the womanís happy family and the fact that she has thus far produced the only male heir to the de Vilers fortune. Equally disturbing is the villagersí appetite to appease the water spirit, Margaretís daughters willing partners with them.
In the end, there are confusions enough for all to deal with, including a history of pagan sacrifices, a colorful exorcism, and a magistrate who can be bought with a promise of his sonís marriage to Margaretís daughter, Cecily. Unfortunately for Lady Margaret, her young son becomes the object of Petronillaís obsession in her quest to become pregnant, putting Margaret and her child in mortal danger.
With Gilbert at her side, Margaret overcomes all with her usual tenacity and forgiving spirit, winning over even the dour Madame who has contracted to subdue the barbaric red-haired girls. Cognizant of the dangers of the religious and political extremes that define the era, Margaret protects her family from assaults on all fronts with the vigor of a lioness.