1380. As the king's parliament debates whether to grant money supplies to the Regent for his war against the French, John of Gaunt orders Sir John Cranston and Brother Athelstan to investigate the murder of the Shrewsbury representatives, as the assassin must be caught before parliament suspects the Regent himself. Unfortunately, Sir John and Brother Athelstan have their own problems to deal with: the coroner is puzzled by a thief stealing cats from Cheapside, while Athelstan is concerned by claims that a devil is prowling his parish. Against a colourful pageantry of medieval court life and the dark slums of London, Sir John and Brother Athelstan pit their wits against a bloody murder and the assassin in the House of Crows.