As the world becomes more and more dangerous, the survivors of the destruction of civilisation and the arrival of terrifying prehistoric beasts must make tough decisions in order to survive. Nurse Alan Graf battles to protect Ellis Webster, the young boy in his charge, as they make their way across a hostile middle England. Former drug addict Nikki Henderson searches for a place she can call home, while increasingly certain she is being followed. In London, streetwise Kenny Green searches for Emily Grenfell, kidnapped by a biker gang, while at Carlton Manor, the survivors must help Mark Raine to rescue his wife and daughter from the fortified town of Marshdown.