Hercules' good name is sullied when his mortal half-brother, Iphicles, steals his identity. As Iphicles joins forces with the evil warlord Gorgus and prepares to marry Rena, Gorgus' stepdaughter, Hercules sets out to defend his name. But Gorgus and the warrior Pallaeus capture Iolaus and throw him into the perilous catacombs. Hercules then has to descend into the labyrinth to save his friend. Fending off booby traps, flying blades and the Mandrake monster, Hercules frees Iolaus. Iphicles' ruse is then discovered by Rena and which prompts him to fight side-by-side with Hercules to regain her love. Finally Gorgus and Pallaeus are defeated.

Alcmene tells Hercules and Iolaus that she is to marry Jason. Hera resurrects the Blue Priest who plans to kill Hercules at the wedding. Meanwhile as Jason must give up his crown as Alcmene is not of royal descent, Hercules sends Iolaus to seek at his half-brother Ipicles, hoping Ipicles can become the new king of Corinth.