 After fleeing the Covenant 's destruction of the human world Reach , the human ship Pillar of Autumn makes a random slipspace jump to avoid leading the Covenant to Earth . Arriving in uncharted space , the crew of the Autumn discover a massive ringworld orbiting a gas giant . When the Covenant attack , Autumn 's captain , Jacob Keyes , entrusts the ship 's AI , Cortana — and her knowledge of defense deployments and the location of Earth — to the supersoldier Master Chief for safekeeping . Master Chief fights off Covenant boarding parties and leaves the Autumn via a lifeboat to the surface of the ringworld while Keyes lands the Autumn on the ring . 
