The game takes place during the Battle of Reach. John-117 fights his way through waves of Covenant forces invading the "Complex." At the end he is picked up by a Pelican, but later shot down. After wandering through a forest, he finds a Warthog. At the end of the ride he gets out and stops a Covenant bomb from destroying a generator. Once the bomb is disarmed, Vice Admiral Whitcomb sends John a transmission saying he's a prisoner on a Covenant ship. Once the Admiral is rescued, John-117 goes to CASTLE Base and saves Sergeant Johnson, who stole an artifact. Together, Johnson and John fight against the Covenant forces until a Pelican arrives to pick them up, carrying them to safety.