In 1298, Edward I of England invaded Scotland and brutally sacked the town of Berwick, razing to the ground the Red House of the Flemings who had permission to trade there. He little knew his action would have far-reaching repercussions. A year later, Edward convokes a great assembly of the realm in St Paul's Cathedral.

They are to hear Mass after which the main celebrant, Walter de Montfort, has been delegated to lecture the King on not taxing the Church. During the Mass, de Montfort dies a sudden and violent death. Hugh Corbett, the King's clerk, is given the task of solving the mystery and tracking down the murderer.

Against the background of Edward's struggle to maintain himself, both at home and aborad, Corbett's investigations become tortuous and laced with danger...