In the final episode of the series Abby and her friends find themselves on the run from Samantha, who has formed a dangerous alliance that threatens everyone's freedom. Meanwhile, Sarah is confronted by a face from the past, which leads her to betray her new friends. When Naj goes missing, the family face the danger of the city in order to find him. Naj is befriended by a feral boy named Darren. Darren lives with the sinister Craig and June, who look after a group of children who forage amidst the ruins of the city in return for the shelter and protection. With his adopted family searching for him in the deserted city, time is rapidly running out, and Dexter is only a step behind them all...

Abby learns of a group of young boys living at a nearby mansion called Waterhouse. She leaves her new friends in order to find her son, Peter. When she arrives at Waterhouse she walks into the middle of a land dispute between an ex-army officer and an aggressive group of teenage boys. She must try and broker a truce in order to discover if Peter is at the house. Tom, Sarah, Al and Najid are drawn to the comfort and security that Samantha's community provides. Things quickly go wrong for Al as he is ejected from the community. Tom sees the chance to prove himself to Samantha, but will his criminal past catch up with him? Greg and Anya have an encounter with some unwelcome visitors that provides a vivid reminder of how vulnerable they are without the group.

Tom and Greg are enslaved alongside dozens of others in Mr Smithson's coal mine. Elsewhere, the Family are desperately tracking Billy, their only lead, across the country. At a roadside motel Billy stops to meet his girlfriend Sally and when the Family confront him, Billy claims ignorance and exits. Meanwhile in the mine, Greg formulates an escape plan, convincing Smithson that he's a geologist and has discovered a gas leak. However the Family are converging on Smithson's as well with their own rescue plans, leading to a dangerous game of cat and mouse...

The post-apocalyptic drama reaches its thrilling conclusion as the fates of the Family, the Lab and the rest of the world come crashing together in a deadly showdown.

Greg has been wounded by a gunshot, Anya, Al and Tom frantically search a nearby hospital to find vital medical supplies. With the building on fire, it suddenly collapses, leaving Anya and All trapped. Whilst Greg is now perilously close to death. Abby still remains kidnapped at the Lab as the Scientists seek to find a vaccine using her immune system.

When visionary spiritual leader John turns up mysteriously at the survivors' door with his ragged group of passionate disciples, some in the house are suspicious of his motives, in the penultimate episode of Adrian Hodges' post-apocalyptic drama series. Charming and eloquent, John is a preacher with a unique perspective on the new world, but the family's opinion of him is split. Is he as innocent as he seems, or does he have more sinister motives? A woman in John's group is pregnant, and Abby allows her to stay until the baby is born. Anya fears that she will be forced to reveal that she is a doctor if there are any problems with the birth. Worse than that, she picks up on some unusual remarks by John which make her concerned for the group's safety.

Britain is in the grip of a deadly flu virus, which is now spreading throughout the world. When people start dying in their millions, a handful of survivors are left struggling to stay alive as society crumbles around them. Abby Grant is a housewife and mother who begins the desperate search for her son. On her journey she meets a variety of people whom fate has spared. The new world could be a dangerous place, and their only hope is to stick together.

The family, scavenging for survival in the city, discover that other people have been abducted in the same way as Abby. Tom, Al, Anya and Sarah set off in pursuit of a pharmaceutical company with offices in the city, while Greg and Naj are confronted by a group from which Tom has stolen supplies. At the lab, Whittaker re-infects Abby with the virus.