York, May 1375. Fear of pestilence has made the city receptive to a newly arrived physician who attacks traditional healers and midwives, reserving particular hostility for the respected riverwoman Magda Digby. At the same time, two long-absent members of Magda's family appear asking for help while concealing their real purpose.
When Magda finds a body near her riverside home, suspicion of murder falls upon her. A warehouse fire then reveals another man who was stabbed before the flames reached him, and Owen Archer must connect the two deaths while countering a campaign that uses medical fear, ecclesiastical support and prejudice to discredit Magda.