The scene is the Dark Ages. The tribes of Britain struggle for survival and warring factions fight for supremacy. Uther Pendragon emerges to become King of Britain, but though he unites the country, the peace he achieves is an uneasy one. Uther takes and marries the Duke of Cornwall's wife and they have a son, Arthur, but they must give him up to Merlin, Uther's visionary advisor. They send Arthur's half-sister, Morgan, to the Abbey of Glastonbury to be raised by nuns, but she becomes bitter and vengeful in the convent She discovers a mysterious power to will things to happen and, as the years pass, her power grows. 

Arthur has a difficult time with the Merlin, but find learning Geography and Philosophy from the back of an airborne falcon more exciting than books and maps. He is raised in the home of Sir Ector, a country knight, and forges a strong friendship with Ector's son, Kay. He also meets "Uncle" Pellinore, king of the Western Lakes, an eccentric who devotes his life to tracking down a fearsome dragon, the dreaded Beast of Borrowdale. 

Morgan escapes from the convent and a chance meeting with Arthur in the forest changes the life of each. He rejects her, she curses him. The curse is to be fulfilled. Meanwhile, Uther's reign ends amidst civil upheaval and Arthur amazes everyone but Merlin by pulling Excalibur from the stone to become High King. Henceforth, he bears his fathers name: Pendragon. 

Guinevere, on her way to Arthur's coronation, learns her destiny from the Lady of the Lake. At the coronation, Arthur makes alliances and exacts pledges of loyalty, b= one of his allies, The evil Sir Malaigaunce, is in league with Morgan. Arthur then falls out midi Kay by refusing him permission to marry a peasant girl. The first part of Morgan's curse is fulfilled. 

Arthur falls in love with Guinevere and makes her his queen, but he is away for long periods and she is tempted by the handsome Malaigaunce. When Arthur returns, Morgan steals Excalibur -another part of her curse fulfilled - and although Guinevere begs him to stay, he goes to search for the precious sword. Guinevere falls into Morgan's hands, is transformed into a Loathly Lady and left to wander the forest, fulfilling the final part of Morgan's curse. Morgan hurls Excalibur into the Lake of Avalon in preparation for Pendragon's destruction. 

Arthur surveys his kingdom from the back of his falcon, realises his misjudgements and castigates himself for his stupidity, and his renewed moral vision enables him to overcome Morgan through a series of trials. He meets the hideous Loathly Lady, who promises to return his power if he grants her one wish in the presence of his court. When he agrees, she leads him to Lake Avalon and Excalibur. In return, she demands his hand in marriage and, when he finally agrees, Morgan's spell is broken and love and harmony reign at the court of Arthur Pendragon as Excalibur rests in the heart of a Round Table.