Paul
Paul is married to Sarah and they have a son, Travis. They live in a home out of the city in the woods where they have attempted to quarantine themselves from the unknown virus that is infecting people. Paul will do anything to protect his family.
Will
Will has a small son, Andrew. Will breaks into Paul and Sarah's home looking for water, food, and supplies. Paul and Sarah eventually help him and his family by letting them move in with them. Like Paul, Will will do anything to protect his family, including holding Paul and Sarah at gunpoint in order to get his infected son away from them.
Travis
Travis is Paul and Sarah's teenage son. He has nightmares about people infected with the virus that is plaguing everyone. He's naturally curious and wants to do the right thing as best he can. He eventually catches the virus and dies from it.
Sarah
Sarah is married to Paul. They live with their son, Travis in their home in the woods where they have quarantined, or attempted to, themselves from the rest of the world because of the virus. She is a gentle woman, but when push comes to shove she is willing to do what is necessary to protect her family including killing Will.
Kim
Kim is Will's wife. They have a small son, Andrew. She moves into Paul and Sarah's home with her family in order to share supplies and create safety by being in a group. She is fiercely protective of her son, and when it seems as though he has been infected she does whatever it takes to get Andrew away from Paul and Sarah for fear they will kill him.
Andrew
Andrew is Kim and Will's young son. He, like Travis, has nightmares while he sleeps. He eventually becomes sick, though we don't see it, and is killed by Paul when he fires a shot at Kim who is carrying him trying to get away from the house.
