Several years after the 2018 outbreak in Truth or Consequences, New Mexico, the Chimera Parasite broke containment and subsequently spread to other areas in the United States, notably New York City, San Francisco, and Alaska. Over the years, the Parasite has adapted to Earth and evolved into the Archæans. Rainbow established a new division, the Rainbow Exogenous Analysis and Containment Team (REACT) and set up containment zones around afflicted areas. As the Archæans grow stronger, REACT must enter these zones to gather any information they can in order to find a way to stop them.