 The blacksmith and swordsmith John (Alan Ladd) is tutored at the court of King Arthur (Anthony Bushell), but as a commoner he can't hope to win the hand of Lady Linet (Patricia Medina), daughter of the Earl of Yeonil (Harry Andrews).The Earl's castle is attacked by Saracens and Cornishmen — disguised as Vikings — and his wife is killed, making him lose his memory.The attack was part of a plot by the Saracen Sir Palamides (Peter Cushing) and the pagan Cornish King Mark (Patrick Troughton) to overthrow Arthur and Christianity and take over the country, whilst pretending to be Arthur's friends and allies - Palamides is a knight of the round table and Mark has faked his own baptism.