When Uther learns the Druids in Cenred's kingdom hold the Cup of Life which can render immortality, he orders Arthur to head an expedition and go snatch it, but Morgana informs Morgause, who alerts Cenred. Arthur and Merlin, with Gwaine who joins them on the way, are captured by slave trader Jarl. They escape during a 'gladiator' duel, but that puts Cenred's men on their trail. While returning with the cup (which the Druids hand over after a mere threat to hurt a boy), they fall in enemy hands. Cenred's men are made an immortal army, while Morgause kills Cenred. This invincible force marches on Camelot, unstoppable, wrecking unseen havoc on the way and in the city. Uther is easily captured. Arthur is wounded but, once healed, starts the desperate journey home, with his two companions, past slain knights.
—KGF Vissers