Halo 3 will pick up where Halo 2 left off. The Master Chief is returning to Earth to finish the fight. The Covenant occupation of Earth has uncovered a massive and ancient object beneath the African sands - an object who's secrets have yet to be revealed. Earth's forces are battered and beaten.

The Master Chief's AI companion Cortana is still trapped in the clutches of the Gravemind - a horrifying Flood intelligence, and a civil war is raging in the heart of the Covenant. This is how the world ends...