Following a failed attempt to contain a riot at a prison in New Baghdad, Atlas releases the Manticore bioweapon in order to quell the uprising. However, instead of killing the rioters, the Manticore bomb reanimates them as zombies. Three platoons are sent in to cage the undead forces, but only one survives, and the others are brought back to an Atlas research facility for further studies. The research is carried out in secret, without the knowledge of the employees