A young woman wakes up after a violent car accident to find both of her children missing. She searches for them and sees several bodies lying on the ground and finds two walkers feeding on a body. They notice her, and one of them begins to chase after her. She then runs to her ex-husband's house and bangs at the door. The door opens, and her ex-husband is standing in front of her pointing a shotgun down at her. He then raises it and shoots the walker that was following her.

The young woman (Hannah) finds children at her ex-husband's (Andrew) house. Andrew, treats her wounds. Hannah and Andrew try to make sense of the chaotic new world that surrounds them. Andrew insists the children stay inside. Disappointed, Billy goes back to the living room and puts the dog bowl down. Meanwhile a rolled up rug with blood on it begins to move and moan.

Judy, Andrew's second wife, walks down the street back to their house with a bag of groceries and we hear an emergency broadcast coming from an abandoned car. She notices a woman lying unconscious on the road beside it. As Judy performs the mouth to mouth resuscitation, the walker bites off Judy's lips. Andrew is heard unloading a shotgun round and then rushing back into his house to wash the blood off of his hands. The power suddenly goes out. He goes to investigate noises and finds the front door open along with a bloody trail leading towards the living room. While searching, Judy appears behind Andrew and he shoots her in the abdomen. He rolls up her body in a rug.

Andrew travels to his neighbour's (Palmer) basement in search of guns and supplies. Palmer asks Andrew why he needs his gun, and Andrew mentions his dog, Max, who has been torn up by the walkers. Palmer tells Andrew he's got more of a problem than his dog and then reveals his wounded leg. Andrew insists that Palmer should go to a hospital, but Palmer mentions that the CDC is searching for a cure and claims that the outbreak was organized by terrorists. He tells him how he had to kill his wife, Maggie. Palmer then explains to Andrew how to operate the shotgun and hands him the weapon as he helps Andrew point the gun at his own head.

Hannah and Andrew prepare to escape to Atlanta. Meanwhile the kids, Billy and Jamie are eating in the dining room. Judy escapes from the rub and appears in front of the children. Billy and Jamie hide under the table to avoid the walker. The children run to the closet for a better hiding place. The walker spots them and begins pounding on the door to get in as Billy and Jamie scream. The walker gets the door open, and just as she reaches out for the children, Hannah comes in with an axe and slashes at what used to be Judy, killing her for good.

What's left of the family decide to go to Atlanta, looking for safety. They all will face the horrifying things that are happening in order to reach their goal. We finally realize who Hannah is in the main series - "bicycle girl" from the first season.