Don and Alice Harris are married, and find refuge alongside a group of estranged survivors in a barricaded cottage. The film remains focused on this group for a lengthy duration, as they struggle to survive and ward off a group of infected "zombies." Eventually, the pseudo-undead overwhelm them, and the few that survive are forced to move to a new location.
The film then scales back. It shows us a more global viewpoint, where NATO forces are sent in to kill anyone in specified vicinities, and they gate down and close down areas. Any survivors remaining are left to fend for themselves. The film than focuses on Tammy and Andy, a brother/sister duo who are estranged from their mother and forced to venture this new dark world alone. Yet a new development occurs. Scarlet and Doyle, two new survivors who come across the children, make the discovery that the children may actually be immune to the disease, and could possibly hold a cure. This causes a domino effect of action and drama, as the disease spreads throughout the commune, and a few select survivors strive to protect the children and get them to a place to be studied.
The film is relentless and unforgiving. Characters die by the handful, and even the main protagonists are only shortly immune to the effects of death and the virus. The film may be too bleak for some, as the ending puts an immediate stamp on the true grimness of humanity. It is an exploration of humanity against all odds, with the Hollywood action staples to capstone the film with intensity.