After surviving a deadly attack on the United States, which killed millions, obliterated the electrical grid and thrust the nation into darkness, Lt. Scot Murphy and his group are about to go full circle. When Sam responds to a desperate plea for help, he is forced to face a familiar menace and fight a brutal enemy that threatens to eliminate all who weren't killed by the nuclear attack. In a post apocalyptic world full of chaos, darkness and struggle, the group must lay aside their differences and work together if they hope to make it out alive.