In the spring of 1312, amidst political turmoil, Sir Hugh Corbett is drawn into a complex web of murder instigated by the ambitions of Philip of France and Edward II of England. As Edward focuses on his favourite, Peter Gaveston, and Isabella anticipates their child, Philip plots murder to further his own ends. Corbett is dispatched to intercept Philip’s master of secrets, but his mission leads him to the mysterious Benedictine abbey of St Michael’s, which harbours dark secrets and valuable treasures, including the “Glory of Heaven” diamond. When the diamond is stolen and murders occur, Corbett, supported by his allies, delves into the abbey’s sinister secrets to prevent further chaos.