Hercules is traveling to Iolcus to instruct King Pelias' son Iphitus in the use of arms. En route he rescues Pelias' daughter Iole from her runaway chariot. From her he learns that her father became king when her uncle was murdered and the palace's treasured Golden Fleece stolen. Hercules and Iole are immediately smitten with each other.
Pelias is warned by a prophet that a man wearing one sandal will threaten his throne. He decrees that if such a man is seen he is to be immediately kille, but when his nephew Jason, the rightful heir, shows up alongside Hercules, having lost a sandal crossing a river, Pelias sends him on a quest to retrieve the Golden Fleece from Colchis, expecting that will be the end of him.
Jason and Hercules set sail with Argus, aboard his ship, the Argo, with a number of sailors, including Aesclepios, Laertes, Caster, Pollux, and Orpheus. They encounter many dangers along the way.