 Pennsylvania suffers an outbreak of the "Green Flu", a highly contagious pathogen that causes extreme aggression, mutation to the body cells, and loss of higher brain functions (essentially zombifying those who catch the flu).Two weeks after the first infection four immune survivors—William "Bill" Overbeck (voiced by Jim French), a Green Beret and Vietnam veteran; Zoey (voiced by Jen Taylor), a college student; Louis (voiced by Earl Alexander), a district account manager, and Francis (voiced by Vince Valenzuela), an outlaw biker—make their way through the city of Fairfield, only to discover that the infection is creating more dangerous mutations in some of its hosts.After narrowly avoiding these new infected, along with hordes of others (as seen in the introduction video), the survivors are alerted to the presence of an evacuation point at the nearby Mercy Hospital roof by a passing helicopter.