The third voume in the Derwyddon series picks up where Cyfaredd Caer Is ends.

Brother Tomos was murdered within the precincts of Caer Is as he translated a venerated manuscript indicating where the Treasures of the Britons has been hidden. Previously, and under the influence of the Potion of the Gods, the Pictish chieftain Talwrch had told his people where to hide these Treasures. These were the Cauldron of Rebirth which gave life and learning to warriors killed in combat; and the Lance of Lleu, the five-headed spear which always hit its mark. It is down to the druid Gwynlan to solve this intricate mystery, but lurking in the shadows are the Mother Church’s brutal agents, Rome’s Holy Vengeance. Their intention is to usurp the druids’ secrets, and use them to undermine the ancient rituals of Caer Is.