Series two picks up moments after the conclusion of the first series. Abby has been taken to the Lab in an attempt to find a vaccine, based on her ability to survive initial infection. Meanwhile, the others scramble to find medical supplies to save Greg.

Abby is still missing. Greg tries to recover from his injuries. Naj leaves graffiti messages around the city hoping Abby will see them. Tom manages to steal some supplies from some rivals. Whittaker re-infects Abby.

The group meet Billy a fifteen year old trader and get some vital supplies from him. The group decide to stay overnight at a cottage to help Abby get over what happened to her. When Billy makes it to Samantha's compound he tells them where the group are staying at. Samantha orders Dexter to go and arrest Tom as she wants to put him on trial for hugging one of her people. Abby, Greg and Anya try and get Tom freed and end up being part of the trial. They soon learn more about Tom's shocking past.

Tom and Greg find themselves enslaved with Kevin and loads of others in Mr Smithson's coal mine. The rest of the gang try and find them and follow Billy who is meeting his girlfriend at a motel. Billy insists that he knows nothing and leaves under the pretense of that he will ask questions about them while on his trading route. Kevin is badly hurt when there is an accident in the mine and Greg comes up with a plan to try and escape. The rest of the gang show up determined to rescue Greg and Tom.

The group head south as they try and find a new home. After meeting a small thriving community of survivors they end up accepting their offer of hospitality. Tragedy strikes though when one of them suddenly dies. Al and Sarah enjoy being together. Tom isn't happy with Anya's new friendship with Judy. Greg and Abby follow up Greg's suspicions about a postcard and they find themselves at an abandoned airfield.

The group find it hard to get over the loss of one of their own. The group meet in an old ruined Laboratory and with a new strain of the virus loose the scientist's work to find a vaccine becomes more important than it has ever been. Abby thinks she has seen her son and is determined to find him. Al decides to be a Guinea pig for vaccine as he thinks he has nothing else to loose. Whitaker continues to cause problems for the group.