Transplanted from ancient Greece to 13th-century Asia, legendary hero Hercules (Mark Forest) takes on the three sons of the great Mongol conqueror Genghis Khan in the years following the death of the fearsome leader. When the sons abduct Princess Bianca (José Greci) from the court of a rival empire, Hercules becomes a prisoner to gain her freedom. Liberated by the sympathetic wife of a Mongol general, Hercules rushes into battle with the sons.