Brother Athelstan - priest of St Erconwald's in medieval Southwark - is praying for a quiet week when he is interrupted by the cry of murder. Hurrying outside, he is confronted by the horrific sight of three mutilated corpses lying on the church steps. Law dictates that if a killer is not found the entire parish will be punished.

Before he has even had time to start his investigation, Brother Athelstan is called to the Assizes on urgent business in his capacity as secretarius to Sir John Cranston, coroner of the City of London. Here, in a bizarre twist of fate, one of Athelstan's parishioners, a respectable widow, stands accused of committing multiple murder and burying her victims in the 'field of blood'.

Certain of the widow's innocence, but convinced that the two incidents must be related, Athelstan embarks on his most perplexing case yet. The consequences, should it not be solved, are unthinkable...