Nashville is falling. Herds are forming. Humanity is facing extinction. They might be the last chance at salvation the city has left. Kate, Storm, and the rest of the Special Forces detachment head to Nashville to bolster the city's final defense, but when they arrive they find that things haven't gone according to plan. They are in a desperate race against the ravages of radiation, the new mutations that seem hellbent on killing them all, and even some of the people in their own group. From the horrors of Nashville to the questionable safety of Fort Carson, Colorado, they will do whatever it takes to survive, find their friends, and search out answers about the deadly government conspiracy that threatens them all. What they don’t know is that they've only just begun, and the threats they've faced so far pale in comparison to what looms on the western horizon.