A decade after his heroic defeat of the monstrous Kraken, Perseus is attempting to live a quieter life as a village fisherman and the sole parent to his 10-year-old son, Helius. Meanwhile, a struggle for supremacy rages between the gods and the Titans. Dangerously weakened by humanity's lack of devotion, the gods are losing control of the imprisoned Titans and their ferocious leader, Kronos, father of the long-ruling brothers Zeus, Hades and Poseidon. The triumvirate had overthrown their powerful father long ago, leaving him to rot in the gloomy abyss of Tartarus, a dungeon that lies deep within the cavernous underworld.

Perseus cannot ignore his true calling when Hades, along with Zeus's godly son, Ares, switch loyalty and make a deal with Kronos to capture Zeus. The Titans' strength grows stronger as Zeus's remaining godly powers are siphoned, and hell is unleashed on earth. Enlisting the help of the warrior Queen Andromeda, Poseidon's demigod son, Agenor, and fallen god Hephaestus, Perseus bravely embarks on a treacherous quest into the underworld to rescue Zeus, overthrow the Titans and save mankind.