As the thriller set in the Celtic mist of the 5th century continues, sleuth druid Gwynlan’s investigation into the heinous murder of Brythonic monks takes him across the sea to Britain, the Isle of the Mighty. Two of the Treasures of the Britons, the Cauldron of Rebirth and the Spear of Lug, are coveted by the Church of Rome, hell bent on eradicating the old druidic faith of the Britons. Under attack from bloodthirsty pirates, Arthur, the Bear of Britain, comes to Gwynlan’s assistance. Aided along a safe but circuitous path by the seer Myrddin, Gwynlan and his retinue avoid the Saxons and reach the Giant’s Dance — Stonehenge — deep in native Durotrigan territory. These ancient stones conceal part of the secret which is puzzling Gwynlan. After a strange revelation, Gwynlan’s path takes him into the deadly clutches of the siren of the swamp where Taran’s life faces mortal danger. Gwynlan’s apprentice can be healed nowhere but in one solitary place, far away in Ordovician lands, reached via the monastery of Deiniol on the shores of the straits, which separate the mainland from Môn, the druids’ sacred island of Anglesey.