Oh sorry I meant 04A.
The series takes place between the events of Halo 4 and Halo 5: Guardians.[10] An Office of Naval Intelligence unit, led by Lieutenant Commander Jameson Locke, is deployed on the distant human Outer Colony of Sedra to investigate terrorist activity. Sedra is described as a backwater world harboring a disdain for the Unified Earth Government and the UNSC. During their investigation, a Sedran city is attacked by Sangheili[11] terrorists and it is discovered that they are trying to use a biological weapon that only affects humans.[12] Locke's team is forced to work together with Sedran Colonial Guard commander Randall Aiken and his troops to track down the origin of the bioweapon. During their search, the unit is drawn to a perilous alien artifact: a partially functioning section of Installation 04, the Halo ringworld destroyed by the Master Chief in the first Halo game. The Halo fragment has begun to orbit in close proximity to a red giant. When the fragment rotates in its orbit, its habitable side undergoes extreme heat that is too unbearable for any human when the habitable side is facing the sun. The fragment's environment only experiences survivable temperatures during the sixteen hours when the habitable side is facing away from the sun, forcing the team to complete their mission within this timeframe.[13][14][15] A grave threat present on the ancient construct soon turns the mission into a desperate fight for survival.[5][16]