When villagers begin disappearing it is discovered that they had fallen through a crack in the earth which goes straight to Hades. Hercules once again comes to the rescue and faces one of his most difficult challenges, and must prove himself as a man as well as a god. "Hercules in the Underworld" is the fourth made for TV movie in the series Hercules: The Legendary Journeys.

The eternal Hercules in this film has gone way beyond his usual time and place in ancient Greece and is now helping Poland free itself of Mongol invaders in the 12th century. Mark Forest is the star of this peplum epic, Hercules Against The Barbarians.