Halo: Reach is a prequel to the critically acclaimed Halo series, and chronicles the the fall of the planet Reach, Earth's last defense against an alien enemy know as the Covenant.
The player character, known as Noble-VI, is part of Noble team, a squad of Spartan-III's who are tasked with the defense of Reach.
At the start of the game, the player character is sent with the rest of Noble Team to check on a communications relay that has mysteriously gone offline, only to discover Covenant forces on the planet. The team moves to defend an Intelligence facility know as Sword Base, where they meet Dr. Catherine Halsey who is the mastermind behind the Spartan programme.
After a night-time operation that reveals the true extent of the massive Covenant Invasion force, Noble assist in the assault of a Covenant ground base. When a massive, unstoppable Covenant super-carrier joins the fight, Jorge and Noble-VI use starfighters to infiltrate a smaller Covenant ship, plant a bomb, and set the corvette on a collision course with the carrier. While evacuating the ship, the timer on the bomb is damaged, forcing Jorge to stay behind and give his life to manually set off the bomb. Victory is shortlived however, as a massive Covenant invasion fleet appears in orbit.
Noble-VI aids in the defense of the city of New Alexandria, before meeting with the rest of Noble team. When all seems lost, they move to retreat to an underground bunker. Kat is killed by a Covenant sniper before they reach it.
On mysterious orders, the team returns to Sword Base, where they are guided to a mysterious artifact by Dr. Halsey, who believes the artifact is key to winning the war with the Covenant. Halsey gives Noble-VI an AI core, housing the artifical intelligence know as Cortana, and tasks the player with delivering the core to a ship know as the Pillar of Autumn. Jun leaves the team to escort Halsey to safety.
En route to the Pillar of Autmun, Carter is severely wounded, and sacrifices his life to give Noble-VI and Emile time to deliver the package. Emile uses a Mass Driver cannon to fight off Covenant ships whilst Noble-VI fights through Covenant ground forces to make it to the Pillar of Autumn. He delivers the package to Captain Jacob Keyes, but iafter Emile is killed by Elites, Noble-VI stay on the planet to help ensure the Pillar of Autumn's escape by operating the Mass Driver cannon.
The Pillar of Autumn escapes the planet, and discovers the Halo ringworld in the process, sparking the events of Halo: Combat Evolved.
After the credits, the player is given control of Noble-VI once more, and must survive for as long as possible against Covenant ground forces. One the player succumbs, a cut-scence shows Noble-VI finally overwhelmed and killed in a heroic last stand. Dr. Halsey narrates the final shot, depicting the players fallen helmet amongst the ruins of Reach.