Three soothsayers command the sorcerer Osgar to give Arthur a rune mark that bears the court of Disir’s judgement over the young king’s rejection of the old religion.
When news reaches Camelot that a valiant knight has been killed, Arthur sets out to capture the man responsible – Osgar. Accompanying the king is the young druid Mordred, who is showing signs of becoming an excellent knight.
Osgar is fatally wounded when he is captured, but before he dies, the sorcerer gives Arthur the rune mark and tells him that he must embrace the old ways or perish.
Back at Camelot, Gaius warns Arthur not to dismiss the warnings. Meanwhile, the dragon tells Merlin that if Mordred is allowed to live, the prediction about Arthur’s death will come true.
Arthur then heads to the sacred lair of the soothsayers, again with Mordred by his side. But when he refuses to appease them, the soothsayers go on the attack, wounding Mordred in the process.
Back at Camelot, Gaius tries to convince Merlin to use his magic to heal Mordred, but he refuses. With Mordred now on his deathbed, Arthur returns to the grove with Merlin to seek the Disir’s forgiveness. But the soothsayers stand their ground and give Arthur until to dawn to join them or accept their original judgement.
When a tearful Merlin advises Arthur that there is no place for magic in Camelot, the young king informs the soothsayers that he will accept his fate. Arthur then returns to Camelot believing he has condemned Mordred to death, but he is overjoyed to find Mordred alive and well. Merlin, meanwhile, realises that Mordred is now free to play his part in Arthur’s death…