The Mists of Avalon is the story of King Arthur told from beginning to end, from the circumstances of his conception to his death, in the perspective of the women in the story. We begin the story with Arthur’s mother Igraine. She is married to Duke Gorlois in Tintagel and lives with her sister, Morgause and her daughter Morgaine. Igraine is the sister of Viviane, Lady of the Lake and high priestess of Avalon. Britain at the time was ruled by a dying High King that had left no heir. As the king lies on his deathbed, all the nobles gather in the city to determine succession. Igraine falls in love with the proclaimed heir to the throne, Uther Pendragon. The Merlin and Viviane planned this, knowing that their fates were twined together. After Gorlois dies in an accident, Igraine and Uther are married. She bears him a son named Gwydion, later given the Christian name Arthur. Arthur spends only a few years in the Uther’s court, cared for and comforted by Morgaine because Igraine was always too busy. Both children are sent to be fostered elsewhere, Arthur in the court of Sir Ectorius, and Morgaine in Avalon.
Morgaine trains as a priestess in Avalon. Avalon is a real island country, but as the years go by, is slowly fading into the mists. Any normal boat sailing towards Avalon will encounter another island that lies in the same place but in another world; there a Christian convent lies. One requires a priestess to banish the mists and allow entrance to the fairy country. Morgaine becomes very powerful quickly for she possesses the Sight and the bloodlines of a great priestess. Viviane decides that she must remain a virgin in order to play the role of Goddess for the Great Marriage to the land. At one point in her young life, Viviane’s son Galahad, also known as Lancelet returns to Avalon. She is asked to escort him for the day and for the first time, she is tempted to break her oath of chastity. She falls in love with Lancelet but that very day, his heart is given to a little girl who had gotten lost from the parallel island and accidentally wandered into the country. Her name is Gwenhwyfar.
In the next year, the Merlin returns to Avalon with dire news. Uther Pendragon is dying and Arthur must be ready to take the throne. It is all in their master plan between the Merlin and Viviane to bring Avalon back to the world. They will make Arthur king, both of the Christians and of the druids and fairy folk. He is brought to Dragon Island for his testing of kingship. He takes the horns of the great stag and runs with the deer; he is the young stag and his test is to slay the king stag with only his wits and a flit knife. Arthur succeeds in the ritual afterwards, he must lay with the Goddess, symbolized by a virgin priestess. The next morning after they make love, Arthur discovers that the priestess is his own sister Morgaine.
Arthur is given the sacred sword of the Druid regalia, Excalibur, along with a magical scabbard that will prevent him from losing large amounts of blood. Soon afterwards, he is crowned High King of Britain. Morgaine, at the crowning, discovers that she is pregnant with Arthur’s child. Afraid and angry at Viviane for manipulating her, Morgaine renounces her ties to Avalon and flees to stay with her kinswoman Morgause. When she bears her child, Gwydion, Morgause takes him away, and distances him from his own mother. Morgaine, in her fever, inadvertently says that Arthur is the farther and Morgause wants to keep the child as a weapon against the High King.
Arthur decides that it is time to marry and chooses the daughter of King Leodegranz, Gwenhwyfar, because her father made the best offer. Unfortunately, Lancelet and her fall in love at first sight, but both are too honorable to do anything about it. In these days, Arthur and his Companions go out often to wage battles against the Saxons. The women, Morgaine included, stay at the castle and spin and weave. Life in the castle becomes routine but Gwenhwyfar still does not bear a child to Arthur. Arthur gives her sanction to betray him with Lancelet, saying that he would accept any child of her womb as his heir. Viviane, aging, loses the Sight and without Morgaine has no one to succeed her. She gets the hatred of Balin when she eases the death of his mother Priscilla, foster-mother to her son Balan. Morgaine disappears into the fairyland, though nobody knows it and Viviane, Gwenhwyfar, and Igraine all seek her. Igraine wishes for her presence as she passes away in the convent.
Arthur and his court relocate from Caerlon to Camelot, where he sets up the renowned Round Table. However, the stubborn Gwenhwyfar refuses to leave with the other women and children because she believes that she is pregnant. She, with her whining and self righteousness Christian prattle, manages to persuade Arthur to forsake his banner of Avalon and carry one of the virgin Mary. She miscarries her child in a fit of rage at Kevin the Harper, successor to the Merlin of Britain. Morgaine attempts to return to Avalon but can no longer summon the barge. She wanders into the fairyland and tarries for about five years. When she returns to the world, peace reigns over the land. All the Saxons have been driven out of the land and Arthur reigns in Camelot. Without wars to fight, the knights play games and joust. One young man, nicknamed Handsome in the court but discovered to be Gareth, brother of Gawaine, is knighted by Lancelet and becomes a fine warrior.
At the feast of Beltane, the companions all return to the castle for a day of games and feasting. Gwenhwyfar begs a charm from Morgaine that will increase her fertility. That night, Arthur in a fit of drunkenness, takes both Lancelet and Gwenhwyfar to his bed in hopes that Gwenhwyfar may conceive a child. Meanwhile in Lothian, the boy Gwydion, an unusually intelligent and perceptive child with the Sight, is taken by Viviane and Kevin to train as a Druid in Avalon. It is Viviane’s plan to set young Gwydion on the throne to succeed his father, the High King Arthur. At the feast of Pentecost, Viviane herself rides to Camelot as a petitioner before the whole court, publicly taking Arthur to task about his betrayal of Avalon. As she stands before the king, Balin murders her with an ax. Her body is taken to be buried at Glastonbury, on the Isle of the Priests.
In the next winter, Melegrant, Gwenhwyfar’s half brother, bastard son of Leodegranz, sets himself up as Lord of the Summer Country and requests an audience with his sister to discuss claim to the land. He tricks them and takes her prisoner. Lancelet returns to save the day, and they lie together afterwards. Lancelet requests leave of the court to go on a quest after King Pellinore’s dragon. Morgaine then contrives for Elaine, Pellinore’s daughter and the Queen’s cousin, to be married to Lancelet using a potion.
Time passes and the peace dwells on. However, Gwenhwyfar becomes ever more pious. She forces Arthur to confess to the Bishop Patricius about the night that the three spent in bed and also for the night of his kingmaking and subsequent lovemaking with Morgaine. Also during that Pentecost, Morgaine is betrothed to the elderly King Uriens of Wales, deceived because she believed that she was marrying Uriens son, Accolon. Morgaine, as Queen in North Wales, reacquaints herself with Avalon and her life as a priestess. Accolon becomes her lover, her consort, and her priest. Morgaine murders Urien’s older son Avalloch using her magic so Accolon may reign in North Wales, all a part of the ploy to return to the Old Religion. Morgaine, after being consecrated again as a priestess, makes a trip to Avalon, taking Lancelet’s daughter Nimue to foster there. Morgaine’s first task is to make Arthur swear anew to Avalon or relinquish his sword Excalibur.
Galahad, son of Lancelet and Elaine, is knighted at the feast of Pentecost. At this very same festival, Gwydion, dubbed Mordred by the Saxons, makes his appearance. He causes a stir by challenging Lancelet at the games and demanding knighthood for his deeds. Morgaine goes to Arthur and demands his allegiance to Avalon, which he refuses. She then asks Arthur to accompany her to her home in Tintagel to reclaim her title as Duchess of Cornwall. Little does he know of her plans for Accolon, her chosen champion, to challenge him. She takes him into the fairyland where Accolon waits; she steals Excalibur and the charmed scabbard as Arthur sleeps. A great battle follows, Arthur gravely wounded survives, but Accolon falls. Her plans ruined, Morgaine leaves Camelot forever and cloisters herself in Cornwall. After many months, she finally returns to Avalon to take her rightful place as Lady of the Lake. One spring after Morgaine’s return to Avalon, the cup of the Druid Regalia disappears, taken by the Merlin. After appearing once in the Great Hall of Camelot, borne by Morgaine, the knights of the Round Table begin the quest for the Holy Grail. Nimue is sent to punish Kevin, bringing him Avalon and given a traitor’s death. As all the other knights set off to seek the Holy Grail, Mordred alone remained at court, insinuating himself into Arthur’s confidence.
After Lancelet’s return from the quest, he can no longer resist his love for Gwenhwyfar. They meet clandestinely, but Mordred plots against them. He proves Gwenhwyfar’s infidelity and Lancelet in a fit of madness murders Gaheris and Gareth who were serving as witnesses. Lancelet and Gwenhwyfar flee from the castle. Mordred turns against his father and in the end, Arthur and Mordred both perish in a fight against each other. Arthur’s body is taken to Avalon by Morgaine and the sword Excalibur is flung back into the lake and the mists from whence it came.