Ten years after his victory over the Kraken, Perseus (Sam Worthington), the demigod offspring of Zeus (Liam Neeson), has settled into a peaceful life as a fisherman alongside his ten-year-old son, Helius. This tranquil existence is marred by the grief of losing Io, his beloved wife. One fateful night, Zeus pays a visit to Perseus and reveals that the divine powers are diminishing significantly, leading to a catastrophic weakening of the gods. The prison walls of Tartarus, where evil is contained, are beginning to crumble due to humanity’s waning faith. Despite Zeus' desperate plea for assistance, Perseus shows little interest in getting drawn back into the battles of the gods.
In the meanwhile, Zeus travels to Tartarus and confronts his brothers, Hades and Poseidon, and his son Ares. Tensions rise as Hades expresses his anger over being exiled to the Underworld, and he refuses to align with Zeus to rebuild Tartarus. Instead, a surprise attack ensues, led by Ares, culminating in Poseidon receiving fatal injuries. Betrayed, Zeus is captured, and in a sinister agreement with Kronos, Hades and Ares strive to drain Zeus of his powers in a bid to revive Kronos, their ominous father.
After a fierce battle with a Chimera in his village, Perseus seeks guidance from the gods, only to find the dying Poseidon who implores him to rescue Zeus with the help of his demigod son, Agenor. In a heart-wrenching farewell, Poseidon bestows his powerful Trident upon Perseus before succumbing to his wounds.
Determined to help his father, Perseus sets off on a journey with Andromeda (Rosamund Pike), who has imprisoned Agenor for his misdeeds. Agenor reluctantly agrees to accompany them, sharing vital information about the legendary weapons forged by the god Hephaestus, instruments crucial for stopping Kronos. The group faces numerous trials, including an encounter with a swarm of Cyclopes, before acquiring a map to navigate through the labyrinth leading back to Tartarus.
The quest takes a dark turn when Ares finds them, resulting in the brutal slaughter of the soldiers protecting Perseus and his party. In a valiant effort, Hephaestus sacrifices himself, allowing Perseus and his companions to evade capture, while Ares continues his quest for vengeance.
Navigating the treacherous shifting paths of the labyrinth, Perseus must confront and defeat formidable foes, including the menacing Minotaur. Finally reuniting with his comrades, the team discovers Kronos regaining his strength, as Zeus suffers from his waning power.
An emotional reconciliation between Zeus and Hades follows as Zeus acknowledges his past mistakes, requesting Hades’ support against Kronos. However, their plans are thwarted as Ares ambushes them, leading to the demise of Zeus in a devastating betrayal.
In the face of overwhelming odds, Perseus and the remaining forces gather for a decisive battle against Kronos and his monstrous army. A spectacular confrontation ensues, culminating in Perseus wielding the combined power of the gods’ weapons to vanquish Kronos once and for all. As Zeus vanishes into dust, he passes his wisdom to Perseus, marking a poignant end to the age of the gods.
As the dust settles, Perseus embraces Andromeda and is determined to train his son Helius to safeguard their land against future threats, forging a path towards a new destiny and potential kingdom, united in their never-ending struggle against darkness.
