In this adaptation of the popular Lerner and Loewe Broadway musical, England's King Arthur (Richard Harris) forms the legendary Knights of the Round Table and marries the fair Guenevere (Vanessa Redgrave). But a plot cooked up by Arthur's illegitimate son Mordred (David Hemmings) to gain control of the throne by pushing together the queen and the much-loved Sir Lancelot (Franco Nero) threatens to topple Arthur's regime.