Remedy for Treason (Roe, Caroline. Chronicles of Isaac of Girona.)

the long version

Girona, Spain, 1353. Struggling to save his patients from the plague, and avoiding the even greater danger of his wife's temper, Isaac discovers that pestilence isn't the city's only killer. A nun dies in the public baths. Then it is revealed that she is not a nun at all, but an attendant to the queen-in nun's disguise. The Bishop of Girona calls upon Isaac to help determine the strange circumstances of her death-and the purpose of her deception. But Isaac soon finds himself and his family caught in a tightening web of royal intrigue designed to destroy the Spanish monarchy-and whoever else gets in the way...