Greek general Themistocles of Athens leads the naval charge against invading Persian forces led by mortal-turned-god Xerxes and Artemisia, vengeful commander of the Persian navy.

A team of U.S. government agents are sent to investigate the bombing of an American facility in the Middle East.

After its victory over Leonidas' 300, the Persian Army under the command of Xerxes marches towards the major Greek city-states. The Democratic city of Athens, first on the path of Xerxes' army, bases its strength on its fleet, led by admiral Themistocles. Themistocles is forced to an unwilling alliance with the traditional rival of Athens, oligarchic Sparta whose might lies with its superior infantry troops. But Xerxes still reigns supreme in numbers over sea and land.

Princess Andromeda is the daughter of King Cepheus, who has gained a victory against the gods. The vengeful god of the underworld, Hades, demands that Andromeda is offered as a sacrifice or he will unleash the Kraken against Argos. A desperate King Cepheus asks demi-god Perseus to find a way to defeat the Kraken. Perseus accepts the challenge because Hades was responsible for his family's death. He discovers that the way to kill the Kraken lies with getting the head of the gorgon Medusa.