In the spring of 1380, the King's own parliament in session at Westminster is debating whether to grant money supplies to the Regent John of Gaunt for his war against the French, and the members of parliament are proving specially stubborn. John of Gaunt orders Cranston to investigate the murders of some of the representatives from Shrewsbury; the assassin is to be caught before parliament levels the finger of suspicion at the Regent and the desired taxes are not granted. Both Sir John and the Dominican priest Brother Athelstan have their own particular problems: the coroner is puzzled by the thief who is stealing cats from the streets and alleyways of Cheapside. Athelstan, on the other hand, is concerned, not only by the disappearance of one of his parishioners but the strident claims of the rest who insist that a devil is prowling the parish of St Erconwald's. Against the colourful pageantry of medieval court life and the dark, foul slums of London Sir John Cranston and Brother Athelstan pit their wits against a bloody murderer and the assassin in the House of Crows.