Halo 3 ODST

The game begins with Dutch, Romeo, Mickey and the Rookie discussing plans for assaulting the Covenant Prophet of Regret's ship above New Mombasa. Buck arrives and introduces Dare. The team enter their HEVs and drop through the atmosphere toward the ship; at the last minute, Dare changes their trajectory to miss the carrier. The Covenant ship enters slipspace, sending a shockwave toward the ODSTs; the Rookie's pod collides with another and crashes to the ground, knocking him unconscious for six hours. He awakens and proceeds to find clues as to what happened to his squadmates.

Buck awakens after the drop and fights through Covenant to find Dare. When he arrives at her pod he finds only her charred helmet. Romeo saves Buck from an Engineer and the two resolve to get out of the city. Dutch drops near a nature preserve and helps Marines while he goes to the city. Mickey commandeers a tank and fights his way along a Mombasa boulevard. Meeting up with Dutch, the two defend an ONI base from the Covenant, blowing a bridge to slow the enemy. However, they are quickly overrun and forced to destroy the facility to keep it from being captured. Fortunately, they are evacuated by a Pelican and they make contact with Buck, arranging a rendezvous at the police headquarters. However, when Buck and Romeo arrive, they see the Pelican get shot down and crash. They rescue Dutch and Mickey, but Romeo is seriously wounded in the fight. The squad hijacks a Phantom transport ship, but instead of leaving the city, Buck decides to turn back and find Dare.

Back in the city, the Rookie is assisted by the Superintendent, which leads him to Dare's position. She and the Rookie team up to reach the Superintendent's data core, which possesses crucial information on something underneath the city that the Covenant is looking for. After fighting through a large Covenant force, they reach the core to find an Engineer hiding within. Dare explains that the Engineers have been enslaved by the Covenant, and this particular one decided to defect to the humans. The alien had downloaded the Superintendent's data into itself and Dare's mission changes from destroying the AI, to escorting the alien to safety. The Rookie, Dare, and the Engineer reunite with Buck and manage to fight their way out of the city. As they fly away in the captured Phantom, the squad watches as the Covenant destroys New Mombasa to excavate the portal to the Ark.
In the epilogue, one month has passed, and the squad is keeping guard over the Engineer in a UNSC orbital station. Sergeant Johnson then arrives, informing the Engineer that he intends to ask it everything it knows about the Covenant and whatever it is they're looking for. If the game is completed at the Legendary difficulty level, a scene after shows the Prophet of Truth overseeing some Engineers uncovering a Forerunner artifact buried beneath the Superintendent's data core.