Three years back, in the peaceful town of Truth or Consequences, a meteorite struck a New Mexico community, unleashing an unknown parasite. A group of operators from Tom Clancy's Rainbow Six Siege banded together to seemingly contain the mysterious parasite during the initial outbreak. Unexpectedly, the Chimera parasite has resurfaced in multiple US sites, deadlier and spreading faster than before. To monitor and prepare for future threats, the Rainbow Exogenous Analysis & Containment Team (REACT), a highly specialized and equipped organization led by Eliza 'Ash' Cohen, Dr. Elena 'Mira' lvarez, and Jordan 'Thermite' Trace, was formed.