Young Prince Valiant (Robert Wagner), son of the exiled King of Scandia, travels to Camelot to become a Knight at King Arthur's Round Table. He hopes to help his father reclaim his throne from the pagan usurper Sligon and restore the Christian faith to their homeland. During his journey Valiant stumbles about the mysterious Black Knight plotting with the Viking pretender to overthrow Arthur. Barely escaping with his life, the young Prince encounters Sir Gawaine (Sterling Hayden), a friend of his fathers, who agrees to tutor him in the skills needed to become a Knight. Valiant and Gawaines relationship is complicated by their romantic involvement with Princess Aleta (Janet Leigh) and her sister Ilene (Debra Paget), daughters of a British nobleman. If Valiant is to restore his fathers throne and prevent the coup detat against Arthur, he must risk everything he holds dear in order to uncover the identity of the Black Knight.