The second volume in the gothic thriller series set in the Age of Saints sees the mystery of the murdered monks deepened for the druid Gywnlan - murders perpetrated because of the monks' involvement with a venerated druid manuscript indicating the location of the hidden Treasure of the Britons. The Church's brutal agents, the Holy Vengeance, are intent on usurping the druids' secrets and using them to undermine the old Celtic religion. Will Arthur and his companions reach the druids' centre of religion on the sacred isle of Mon?