In 1312, Sir Hugh Corbett, Keeper of the Secret Seal, returns to a Westminster thrown into chaos by the flight of Edward II, who seeks to protect his favourite from noble wrath. The situation worsens with the discovery of a poisoned royal clerk, dead in a locked room. Simultaneously, a series of murders and disappearances at the Convent of Saint Sulpice draws Corbett into a deep investigation that ties both mysteries together. His quest leads him to confront the dangers of a high-class brothel and its dangerous owner, Mother Midnight, while being targeted by a deadly guild of assassins. Surrounded by a web of murder, Corbett must rely on his intellect and resourcefulness to prevent further disaster.