After saving the life of his royal father's usurper, Pelias (Douglas Wilmer), whom he fails to recognize, Jason (Todd Armstrong) is encouraged by the conniving murderer to begin a quest in search of the Golden Fleece. In doing so, Pelias hopes for Jason's death to thwart the prophecy that he will reclaim the throne. Along the journey, Jason is protected by the goddess Hera (Honor Blackman), and his crew includes Hercules (Nigel Green) and Acastus (Gary Raymond), a saboteur planted by Pelias.