Abby is taken to a sealed bio-dome where scientist Fiona Douglas tries to find out how she caught the virus but survived. James Whitaker tells her her cooperation is crucial but he is a liar who says his wife and child are dead whilst he is secretly hiding them. Anya and Al are trapped under rubble in a decaying hospital where they have gone for her to operate on Greg. They survive when Sarah agrees to have sex with a man who will help them and Anya removes the bullet from Greg, who then denounces Tom as a murderer,causing Tom to leave the group.

Tom returns to the group with supplies, having seen gun-wielding men in gas masks round up other survivors into a van marked PSJ Laboratories, where Abby is being held and to which they travel. Whitaker has Abby re-injected with the virus to see how she survived, in order to make the cure. Once again she survives. Whitaker's wife, whom he has kept hidden until a cure is found, accidentally stumbles on Abby and other guinea pigs and is horrified. She cannot save the other captives but releases Abby,who returns to her friends.

When the group's Land Rover breaks down they are helped out by wheeler-dealer Billy, who knows everyone - including Samantha, to whom he betrays their position.She has Tom put on trial for killing her man Gavin and it comes out that he was originally in prison for committing a double murder during a robbery. Samantha says she will release him if he kills Dexter, who is becoming a liability to her. He does so but she reneges, sending both him and Greg to become slave labour in coal mines owned by Smithson, a friend of the duplicitous Billy.

The family attempts to free captives Tom and Greg from Mr. Smithson's Coal Mine.

Greg follows a clue as to where his wife may have gone,to an airfield used to ferry out plague survivors. Here Mr.Stevens,who missed the plane and went mad, kills himself. The rest of the group encounter a commune of survivors,living an idyllic self-sufficient life-style,but a mutant strain of the virus hits one of the families,and Sarah,who has quarantined herself in their house to prevent contagion,dies with them.Abby burns the house and the outbreak - spread by birds according to Tom - is contained. Leaving Sally with the commune the other survivors go to ...

Fiona Douglas is the sole survivor in the lab, working on a cure. She tells Abby that Peter,immune like his mother, had been to the lab with Whitaker but both had left. She does not know who Landry, the man with whom Whitaker communicates, is but believes she has perfected a serum,which is successfully tested on Al.Whitaker has hidden Peter in a caravan park,telling him to shoot strangers and the boy kills Fiona. Whitaker takes him to the airfield to give to Landry - whose company accidentally caused the virus, but the survivors follow and Peter is exchanged for the ...