Halo 5: Guardians is a first-person shooter video game developed by 343 Industries and published by Microsoft Studios for the Xbox One. The fifth mainline entry and tenth overall in the Halo series, it was released worldwide on October 27, 2015. The game's plot follows two fireteams of human supersoldiers: Blue Team, led by Master Chief, and Fireteam Osiris, led by Spartan Locke. When the former goes absent without leave to track down the artificial intelligence construct Cortana, Master Chief's loyalty is called into question, and Fireteam Osiris is sent to retrieve him.