While the group is engaged in diverting a massive horde of the infected from overrunning the camp, a fragment of the Wormwood Comet slams into the Earth. Though the impact distracts the horde, the entire Midwest eventually falls under the cover of darkness. Without the sun's warming rays, the group is plunged into an arctic cold. Their solar array is no longer effective, and they must battle the elements to solve their new dilemma. Meanwhile, new creatures begin to emerge from the forest, bringing them more problems and danger. To make matters worse, one of the group may have been infected, and it is only a matter of time before the unthinkable happens.