The musical, based on T.H. White's The Once and Future King, chronicles the legend of King Arthur (Richard Harris) and his tortured love affair with his queen Guenevere (Vanessa Redgrave). Arthur first encounters Guenevere, on the day of their wedding, in the enchanted forest surrounding Camelot. After the wedding, Arthur's bliss at his marriage to the lovely Guenevere prompts him to establish the Knights of the Round Table, a lofty order of chivalry in which all the member knights are bound by a desire the help the oppressed, keeping faith with trust and honor. Such is the fame of the Knights of the Round Table that a young French knight, Lancelot Du Lac (Franco Nero), seeks to join the order. Lancelot quickly becomes the most celebrated of all the knights, and Guenevere, aloof at first, falls in love with him. Although both have a deep love for Arthur, their passion knows no bounds, and they begin an illicit love affair behind Arthur's back. Arthur ignores the rumors circling around him, but when his illegitimate son, Mordred (David Hemmings) arrives at Camelot, he exposes Lancelot and Guenevere during a tryst. Lancelot escapes, but Guenevere is sentenced to be burned at the stake. Lancelot rescues her at the last minute, and Arthur prepares for battle, his dreams of an idealistic Camelot shattered.