Mordred, King Arthur's illegitimate son and nephew, has often been portrayed as a traitor who kills Arthur and causes the downfall of Arthur's kingdom. In The Wicked Day, her fourth volume on the King Arthur myth, Mary Stewart challenges readers to reconsider the character of Mordred and his role in Arthur's demise. She traces the protagonist's ill-fated life from his beginnings as an orphan raised by fisher folk, to his rise to power as Arthur's trusted counsellor and regent and finally to the choices and circumstances that bring about the "wicked day" of destiny. The strength of the book lies in Stewart's depiction of Mordred as an intelligent and loyal person unable to escape his fate. After he discovers his identity, Mordred learns of Merlin's prophecy that he will one day become Arthur's bane. Queen Morgause, Mordred's mother and Arthur's enemy, endeavors to recruit her son to oppose Arthur. Nevertheless, Mordred vows to fight fate and the gods and earns the trust of his father. Only Mordred's ambition for a queen and a kingdom brings him to the brink of catastrophe where his choices mean the end or fulfilment of all his hopes and dreams.

While readers will enjoy The Wicked Day by itself, I suggest reading Stewart's prior Arthurian novels first to appreciate established characters such as the wise yet weary Arthur and the devious Queen Morgause. Moreover, the other books will also show readers the deep-rooted seed of the Arthurian tragedy beginning with Mordred's parentage and bearing fruit in Morgause's family and Mordred's life. Finally, readers could also compare Stewart's Mordred with her books' other heroes such as the young Merlin in The Crystal Cave and Arthur himself in The Hollow Hills.