Ruth Galloway's friend Cathbad is house-sitting in the Norfolk village of Walsingham, famous as a centre for pilgrimages to the Virgin Mary, when he sees a strange vision of a young woman dressed in blue he thinks may be the Madonna herself. The next morning the woman's body, dressed in a white nightdress and blue dressing gown, is found in a ditch. DCI Nelson and his team are called in and establish that the dead woman was a recovering addict being treated at a nearby hospital. Then Ruth is contacted by an old friend, now a priest, who reveals that she has been receiving vitriolic anonymous letters containing a phrase about a woman "clad in blue, weeping for the world". And when another woman is murdered, Ruth realises she is tangled up in a grisly mystery...
