King Androcles of Thebes commands a ship in search of a threat to Greece, predicted by an atmospheric oracle. Hercules is part of the crew, but the strongman falls overboard in a thick fog. Washed ashore, he saves a young Ismene from Proteus, an evil, shape-shifting creature. Ismene takes Hercules to Atlantis, where he discovers that her mother, Queen Antinea, has captured Androcles. Hercules schemes to rescue him and thwart Antinea's dream of world conquest.

Directed by Vittorio Cottafavi