Halo: Nightfall

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.