A Persian horde is poised on the plains of Marathon, set to massacre the population of Athens. Led by the bloodthirsty dictator Darius, the invading army outnumbers the defenders six to one. Despite these insurmountable odds, Athenian champion Philippides refuses to abandon hope. Embarking on an arduous journey to Sparta, the hero tries to enlist the help of the neighboring army before taking to the battlefield to defend his people. Betrayal, cunning and bloodshed mark the final epic clash as the armies rage across the battlefield to the seas and underwater.

The Giant of Marathon (released in Europe as La Battaglia De Maratona) stars Steve Reeves, a pillar of the sword and sandal genre, as the hero Philippides. Director Jacques Tourneur's long-spanning career included such genre classics as Cat People, I Walked With a Zombie and Curse of the Demon. Italian horror legend Mario Bava is responsible for the stunning cinematography, which propels the gruesome battle scenes.