Merllyn is missing. Guinevere, bewitched and seduced by Launcelot, has retreated to a silent order of nuns. King Arthur, mortally wounded and with most of his knights killed at the battle of Camlann, is taken to the Isle of Avalon from where he cannot return. Cast into the lake, Excalibur falls into the waiting hands of the "Lady of the Lake." The beautiful Lady Helen of York is betrothed to Sir Galahad before they set out on a quest to find and rescue Merllyn from the clutches of the evil witch, Nimue.