A mysterious virus kills most of the world. In England Abby Grant finds herself immune but her husband dead. She determines to set out and find her son Peter, last known holidaying in the Peak District,and on the motorway meets the practical Greg Preston. Tom Price, a convict serving life for murder, kills the only other prison survivor, a warder,and escapes, meeting Anya, a hospital doctor who has seen friends and patients alike die. Al, a wealthy young man, also survives, 'adopting' Najid, an eleven year old orphan. The group ultimately come together whilst Samantha...
The group set up camp in a big house from where they send out a scavenger party to a supermarket but are forced to withdraw by another, armed, group. Abby believes one of the men may have information about her son but she gets no joy. Greg, meanwhile, comes across a warehouse full of food and a couple, Sarah and the injured Bob.
Following the sighting of a helicopter and an encounter with a family who have put themselves in isolation the group links up with Samantha Willis and her community. Initially she and Abby get on well and she asks Abby to stay but Abby is unhappy at the other woman's ruthless attitude and besides, she needs to press on and look for her son, Peter. In a laboratory in Samantha's complex scientists are trying to develop a vaccine for the killer virus.
In pursuit of Peter Abby leaves the others and travels to a country house where Jimmy Garland is heading a group of teenage boys but Peter is not among them. Most of the rest of the group are attracted to the comfortable life-style offered by Samantha's community and are keen to stay but Al is ejected and then Tom also falls foul of Samantha and the party have to move on.
The survivors are living in a country house when a band of, chiefly young, people turn up, a ragged crew 'led' by John, a supposed visionary. Despite initial misgivings Abby lets them camp in the grounds where Al tries to get cosy with one of the girls, Louise.Another girl, Linda, is heavily pregnant. Anya is worried about revealing that she is a doctor because of the value this will place upon her but nonetheless delivers Linda's baby. John becomes increasingly bizarre in his behaviour and is eventually revealed to be a paranoid schizophrenic.
The group is forced to leave their country house headquarters when Sarah betrays the fact that Anya is a doctor and Tom kills one of Samantha's men. They relocate to the city where Naj gets lost and is eventually found,having been taken in by Craig, a sort of Fagin figure who, with his partner June, gives boys a home in exchange for what they can scavenge. The other survivors take Naj from Craig but are ultimately tracked down by Samantha's people in a rooftop car park where Greg is shot and Abby is captured and driven away.