In 1311, four years after the death of King Edward I, his former bodyguards continue to guard his secret relics and a mysterious prisoner within the secluded Holyrood Abbey in the Welsh March. The tranquillity of their existence is shattered by the poisoning of Abbot Henry. Following this, Sir Hugh Corbett, Keeper of the Secret Seal, is summoned to investigate the chaotic scene at the abbey, where he discovers more victims of brutal killings. Amidst a violent snowstorm and the arrival of two significant but unwelcome figures – the Marcher Lord Mortimer and King Philip of France’s envoy De Craon – Corbett is pressed to solve the mystery. As the body count rises, Corbett faces the challenge of identifying and stopping a malevolent force intent on transforming the abbey into a scene of murder.