The story is set shortly after Emergence Day, when the Locust Horde first attacks the planet Sera. It focuses on Kilo Squad, led by Lt. Damon Baird, with members including Pvt. Augustus “Cole Train” Cole, Sofia Hendrik, and Garron Paduk. The game’s narrative is framed as a military tribunal, where each squad member is on trial for disobeying orders. The game’s story unfolds through the testimonies of Baird and his squad members during their trial. Each character recounts their version of the events, which serves as the basis for the game’s levels. Kilo Squad is accused of treason after they defy orders and deploy a Lightmass Missile to destroy a Locust-controlled city to stop a new type of enemy called the Rager. The final section of the game reveals the squad’s actions as they attempt to survive the Locust onslaught and prevent the Ragers from reaching the human population.