Sister Fidelma and her husband Eadulf are journeying back from the Kingdom of the East Angles to Cashel when a violent storm wrecks their ship on the Isles of Sulis. Seeking shelter, they discover that Lowarn, the ruler of the islands, has been poisoned in an assassination attempt, but who is the culprit? And what are their motives? Lowarn’s sister, Sirona, begs Fidelma to investigate the case, while Eadulf uses his medical skills to tend to the dying king.