War has spread throughout the world and the Metti virus consumes every continent. Attackers must now defend their own borders and alliances crumble as greed consumes the strong. A threat is kept, and a weapon known as The Grey Sheet is deployed as a final desperate attempt at victory. Even an unlikely alliance between sworn enemies may not be able to stop what's coming.

Lieutenant Miguel Alverez is a broken man. Through retreat and defeat at every turn he has been given one final mission: To take a group of survivors to the mountains of New Mexico where the last American stronghold lies. Plans change however, and when his plane is shot down and those that survived are ambushed all seems lost until a thin, bearded man called Jonathan Fisher comes to their rescue. The untrusting man with a killer's eyes, along with his group of escaped prisoners, Civil War reenactors, and a strange, quiet child with a tattooed forehead make him uneasy. He must decide if he is their ally or their detainee, and When Fisher's camp is attacked by the RSSR he must decide whether to escape or risk his own life to help defend the strangers.

The conclusion of Atrum Terra takes the survivors down the countryside of America and across seas. Through foreign invaders, Metties, desperate wild animals, even the very Earth attacking them at every corner, none may survive the Dark End.