 The Brotherhood of Steel is a faction of technologically advanced pro-human soldiers who survived the nuclear holocaust. During an exodus to the west, a section of the Brotherhood is cut off from the main group in a thunderstorm. The separated group, never to see the main group again, establishes itself in Chicago and proceeds to carry out its original mission: to tame and assimilate the confused and wandering inhabitants into their ranks. Strongly biased against the non-human beings of the wasteland, the Brotherhood realizes it has to work hand in hand with them in order to combat a new, deadly opponent.