Harriet Ambrose, a government technician, is travelling from London to Sheffield, aware of a pending cataclysm. As the train she is on enters a tunnel, a meteorite the size of Birmingham strikes the Earth.

The survivors explore the ruins of Sheffield city centre in a search for friends and family, but find no survivors. The group desperately needs to find a supply of fresh water, and Harriet leads them to the bunker, and possible salvation. They are confronted by evidence of fellow survivors, but it is of an unwelcome nature.

The survivors head out of the city towards the Ark, and search for food and water. A trip to an abandoned factory complex has tragic consequences.

Jandra is seriously injured, but the group needs to press on with their journey. Their progress is blocked by an unfordable river, but Hild leads her new friends to medical facilities, and into danger.

The travellers take refuge in a village and meet the last survivors of a failed community, but their hosts present a threat to the group and the hunters are in pursuit.

The survivors reach the Ark, where they discover the truth about Hild's people.