Episode 1 Ninety-nine per cent of the population are dead, Abby has been kidnapped and Greg lies badly wounded - can things get any worse for the Family? Greg has been shot, and Abby abducted by masked men from a secret laboratory. Anya realises that they will need medical equipment to save Greg's life and she leads Al and Tom into a hospital, where they face both the threat of disease from long-dead bodies and a raging fire. During their search the building collapses, burying Al and Anya under the rubble. As Tom mounts a rescue attempt with Sarah and Naj, Greg lies perilously close to death. Elsewhere, Abby finds herself a prisoner of Whitaker, the obsessive leader of the Laboratory scientists. They have all escaped infection and hope to synthesize a vaccine from her blood, but none are aware Whittaker has secrets of his own. In the city, the Family realise they will need the help of other Survivors if they are to rescue their friends.
Episode 2 With the clock ticking on how long the Family can remain in the dangerous city, Tom leads a desperate attempt to find Abby. With Abby still missing and Greg recovering from his injuries, the Family are left scavenging for survival in the city. While Naj leaves graffiti messages for Abby, Tom steals supplies from other survivors. The Family learn that more people have been abducted like Abby, and that the kidnappers bear the markings of a known pharmaceutical company. As Tom leads Al, Anya and Sarah off on this trail, Greg and Naj find themselves confronted by the group Tom stole from. In the Lab itself, Abby is re-infected by Whitaker, who will stop at nothing to find his miracle vaccine.
Episode 3 Tom's brutal past is finally revealed for all to hear, and the group is confronted with the reality of the man it has harbored.
Episode 4 When dozens of people are enslaved in a coal mine, Greg formulates an escape plan which leads to a dangerous game of cat and mouse.
Episode 5 When the group travels south to look for a new home they encounter a small but thriving community of survivors. After some initial trepidation they decide to take up their offer of hospitality.
Episode 6 With a new strain of the virus loose finding a vaccine is more important than ever - so Abby agrees to provide whatever samples are needed to create a cure.