The warlock agrees to help a young druid boy, Daegal, although to do so he has to leave Camelot on a dangerous mission -- just as the citadel is playing host to the fearsome Sarrum of Amata. He hopes no one will notice his absence, but as the sky darkens so do Merlin's suspicions -- is there more to Daegal than meets the eye? And can a man as ruthless as Sartre be trusted? (TV Guide UK)