The story of the game takes place 20 years before the events of Halo: Combat Evolved, detailing one of the first encounters between the human United Nations Space Command (UNSC) and the collection of alien species known as the Covenent. The campaign mode follows the UNSC ship "The Spirit of Fire" and the crew's struggle with the Covenent. Of course, everyone's favorite space plague The Flood will be making a (non-playable) appearance in the game.