Sam Baron just freed Orkney from the ravages of the Red Sun—but now, imprisoned by Catriona, leader of the Volgrim Witches, Sam finds the darker side of his half-god, half-witch heritage released, and he fears he might destroy what he saved. Unable to resist the witches' enchantments, Sam has become their most potent weapon, and is leading an army of monstrous men against Skara Brae. Sam’s only hope for salvation lies with his three best friends and a mystical artifact known as the Moon Pearl. Keely travels north in search of the pearl, while Howie prepares for the gathering onslaught. Leo seeks a powerful artifact in the underworld, and faces an ancient evil that could be an even greater threat than Catriona and her cronies. As Sam's friends rush to save him, other forces are at work in Orkney's shadows—forces that could help free Sam, or condemn him to the darkness forever.