When a mysterious epidemic breaks out in Atlanta, an urban quarantine is enforced, leaving those inside to fight for their lives as local and federal officials search for a cure. Police officer Lex Carnahan works to keep the peace, but the situation becomes personal when he learns his girlfriend Jana and his best friend Jake are both stuck in the cordoned area. Also trapped with the infected are 17-year-old Teresa, who is very pregnant and separated from her boyfriend, elementary teacher Katie Frank, who is on lockdown with her entire class, and CDC researcher Dr. Victor Cannerts. Public trust deteriorates as a journalist, Leo, begins chasing down a conspiracy that unravels the official story.