The game is action based; far outweighing any of the role playing elements that are included in the title. Fallout: BOS takes place in a post-apocalyptic setting. The idea behind it all is that the world is in turmoil due to atomic bombs being dropped all over the place. Various humans have survived by staying in vaults underground, while others have turned into mutants by living on the toxic covered surface. The Brotherhood of Steel are a group who have come to fight against the mutants, specifically against a plot to kill all humans with a special weapon.