In a matter of weeks, Massachusetts has been overrun by an insidious rabies-like virus that is spread by saliva. Those infected quickly lose their minds and are driven to bite and infect as many others as they can before they inevitably succumb. Dr. Ramola "Rams" Sherman receives a frantic phone call from Natalie, a friend who is eight months pregnant. Natalie's husband has been killed—viciously attacked by an infected neighbor—and in a failed attempt to save him, Natalie, too, was bitten. Natalie's only chance of survival is to get to a hospital as quickly as possible to receive a rabies vaccine. The clock is ticking for her and for her unborn child. Natalie’s fight for life becomes a desperate odyssey as she and Rams make their way through a hostile landscape filled with dangers beyond their worst nightmares.