S1, E1: High King Uther rages at his bastard son Arthur and exiles him. Arthur finds a young boy, Derfel, close to death. He leaves Derfel in the care of Merlin and his prodigy Druidess, Nimue. Eight years later, Uther has a new heir. Merlin sees a vision of terrible destruction in newborn baby Mordred’s future. Derfel is shocked to re-encounter the man who attacked him as a child, Gundleus.