Plague of a Green Man

A Lady Apollonia Mystery by Ellen Foster.

In this novel set in Geoffrey Chaucer's England, the year is 1380 and winter is approaching. The Lady Apollonia of Aust is living in Devon while her three younger sons attend Exeter's cathedral school. Her husband, the franklin Edward Aust, is required to be in London while the Lady works with his steward to manage their family's expanded investments in Devon's growing wool trade. Lady Apollonia encounters a mysterious aura of antagonism, hovering amidst the guild members of Exeter whom she meets. Inside the Cathedral Close, she realizes that threats against the dean and chapter have already begun to appear within the chapels of the great church.
Lady Apollonia not only seeks to understand the meaning of a green man but also to determine why foliate faces, used to corrupt official pardons of the church, should remain her best clues to discover the truth of a plague of intimidation and death infecting all classes of the city.