Following a head injury sustained during a storm, Hank Martin (Bing Crosby) comes to in Camelot in the year 528. Thought to be a criminal, Hank is brought before King Arthur (Cedric Hardwicke) and the evil magician Merlin (Murvyn Vye). Using his knowledge of technology, Hank convinces everyone that he has special powers. After falling for the lovely Alisande (Rhonda Fleming), Hank must duel with her fiancé, Lancelot (Henry Wilcoxon), and save the king from Merlin's fiendish scheme.