Ex-Marines Sam Reynolds and Chad York are at a remote pharmaceutical plant in Colorado negotiating a contract for their security company, when a deadly viral epidemic sweeps the continent, becoming a global pandemic of apocalyptic proportions. Several months pass by, and Sam and Chad decide that the contagion has run its course. They have formed relationships with Jill Myers and Laura Willis respectively, and the four of them set out to see if any of their families have survived what has been a near extinction event for the human race. An odyssey begins, and along with Sam's mother, a widowed gas station owner and his dog, and an orphaned teenage boy, they head west towards Carmel on the Pacific coast, in the hope of finding Jill's parents alive. Chaos rules in what is the beginning of a new age amid a burgeoning population of indigenous fauna and animals that were released from zoos and wildlife parks when the virus struck. The trek west is fraught with life-threatening incidents, as the group has to contend with deranged survivors in general and Willard Boyd - a homicidal psychopath who is on their trail and determined to kill them - in particular. Some members of the group will not make it to their intended destination, as any mistake or lack of vigilance is punished swiftly and unmercifully with violence and death, which visits them in myriad forms.