Sir Josse d'Aquin is summoned to assist the beleaguered King John in the 17th – and final – Hawkenlye mystery. September, 1216. A foreign army has invaded England. The country is divided. Some support the rebel barons and Prince Louis of France; others remain loyal to the king. His rule under threat, King John summons Sir Josse d'Acquin to support him. But can Sir Josse save the king from himself? Meanwhile, Josse's daughter Meggie is summoned to Hawkenlye Abbey to attend a sick patient in a very distressed state. The elderly woman is warning of terrible danger unless she can complete her mission. What she learns from her patient will set Meggie on a perilous journey to retrieve a cursed treasure. But will she be in time to prevent a tragedy?