Locke and his ONI squad – along with Colonel Aiken and his Sedran Guard – are still trying to make it to their crashed ship. But the deadly, technology-seeking Hunter worms that inhabit this chunk of Halo ring are whittling the team down. As more team members fall victim to the Hunter worms, the remaining members face the possibility that not everyone can be rescued, and team alliances begin to form. Tensions rise, and Locke and Aiken have to try and keep their teams together long enough for any of them to survive.
Halo: Nightfall introduces a pivotal new character, Jameson Locke, a legendary manhunter and agent with the Office of Naval Intelligence (ONI), Earth’s most powerful and secretive military branch. When he and his team are caught in a horrific biological attack, they unravel a plot that draws them to an ancient, hellish artefact, where they will be forced to fight for their survival, question everything, and ultimately choose between their loyalties and their lives. Taking place between the events of Halo 4 and Halo 5: Guardians, Halo: Nightfall is Locke's origin story which will lend insight into the character he becomes in Halo 5.