When Ruth's friend Cathbad sees a vision of the Virgin Mary, in a white gown and blue cloak, in the graveyard next to the cottage he is house-sitting, he takes it in his stride. Walsingham has strong connections to Mary, and Cathbad is a druid after all; visions come with the job. But when the body of a woman in a blue dressing-gown is found dead the next day in a nearby ditch, it is clear Cathbad's vision was all too human, and that a horrible crime has been committed.