Several years since a zombie virus swept across America, there's only one person -- who goes by just Murphy -- known to have survived the infection -- the world's last hope at creating a vaccine. The last functioning viral lab needs blood from him for its antibodies, but the facility is in California and the man is in New York. A ragtag group of strangers works to transport him to the West Coast, but his dark secret remains hidden, which could threaten everyone. Hammond and his second in command, Garnett, initially lead the group of the living -- later replaced by Lt. Warren -- and computer hacker Citizen Z helps everyone navigate through the zombie-infested terrain. When the group meets a man in Colorado, he offers to take Murphy the rest of the way to California. When nuclear weapons are launched, people head into survival mode and become desperate to find a cure.