The scene opens up in Atlanta where a few zombies are eating at the leftovers of Rick's horse from the series pilot episode. A black helicopter flies overhead that attracts the attention of one female zombie. Rising and following in the helicopter's direction, other zombies follow her. This small group of zombies continues through the city, gathering more zombies as they exit the city limits. But leaving the city doesn't hinder the horde's ability to have it's numbers grow. Eventually there are hundreds and perhaps thousands of them wandering through the state. During one dark night the horde is going through some woods. They are groaning and shuffling when a gunshot is heard. Every zombie stops and turns their heads in the direction of the blast. As they exit the woods, we can see Rick and Carl a few acres ahead of them.
Daryl and Glenn arrive back at the farmhouse first and inquire where Rick and Shane are. Daryl informs them that they encountered Randall as a Walker and that Shane wasn't telling the full truth about the situation. The revelation that Randall was a Walker but didn't have any bitemarks on him was also mentioned and thought on.
In the field, Carl is questioning his father about how Shane died. As they walk back toward the farmhouse, Rick never answers his son's questions. Finally he pauses to tell him but hears something and turns his head to see the zombie horde not very far away.
Unwilling to lead the horde directly to the farmhouse, Rick leads Carl to the barn where they can at least have some protection. Rick locks the main barn door and begins to work on a plan. Dumping as much gasoline on the barn floor as possible, Rick give a lighter to Carl and sends him up to the loft. On his signal, he wants Carl to drop the lighter. Rick throws open the doors and lures the zombies in and makes his way to the ladder to the loft. Carl drops the lighter on cue and the whole floor area, Walkers and all, goes up in flames. Rick and Carl stand on the loft and watches.
The arrival of the zombie horde does not go unnoticed at the main house. Herschel tells them to kill the lights and get ready. Some decide to use the vehicles to lure the Walkers away while Herschel is going to stand his ground and fight. Taking his shotgun, he finds his place just a few feet from the porch.
As the group drives about shooting the Walkers, Daryl figures that Rick and Shane might be up in the loft. Perhaps Carl is too since Lori had discovered that he isn't in the house. Daryl tells Jimmy to take the RV around the back of the barn to see if they are there. As quick as he can maneuver the RV, Jimmy gets around back. Rick and Carl works their way onto it's top but on the inside, the Walkers have gotten in and kill Jimmy. As Rick and Carl get onto the ground, Jimmy's blood is splattered in the glass, confirming to Rick that whoever was driving was beyond saving.
It becomes apparent that the plan corral the zombies won't work. The truck T-Dog is driving circles back to the farmhouse to gather the others. Herschel won't leave his post and continues to take down Walkers. Lori, Patricia, Beth and Carol tries to get to T-Dog's truck but the Walkers are everywhere. Patricia is grabbed by them and torn right out of Beth's hand and killed. Andrea, who has been literally riding shotgun in T-Dog's truck, comes out and tries to make a way for them. Carol get pinned against a wall with nothing but a board for protection but Andrea saves her, though she ends up getting taken down to the ground by some Walkers.
The other women get inside T-Dog's truck and he leaves thinking Andrea is dead and not knowing where Carol is. Daryl however, arrives and rescues Carol on his motorcycle. It's also at this time that Glenn realizes that the farm is lost. He tells Maggie, the one that is driving Shane's SUV, to get off the farm now. She doesn't want to leave her family behind but Glenn convinces her that they cannot stay.
It looks like Herschel is not going to make it but keeps unloading all her has on the horde. Rick saves him from behind and tells him to come with them. It pains him to do it, but Herschel follows. Andrea tries to flag down Rick as he speeds away but isn't seen. She grabs the bag of weapons and runs for the woods as dozens of Walkers follow her.
After the sun rises; Rick, Carl and Herschel arrive at the spot on the highway where they had left some supplies for Sophia. After fighting for some hope, they are rewarded with the arrival of the survivors. Considering all that could have happened, there were only three losses of the night: Shane, Jimmy and Patricia.
With no definite direction to go, they go east on T-Dog's suggestion. They would just have to try and stay off the main highways to avoid any large groups of Walkers. The early day does not find Andrea well however. She is able to stay ahead of the Walker and even take out some but their numbers are relentless and keep on her the whole time.
By evening, Rick's vehicle is almost out of fuel and they small caravan of survivors stop. Rick takes charge and decides to stay the night there and make camp at a nearby wall enclosure. Most of the group isn't happy with this but their options are very limited. The topic of people becoming Walkers but not bit comes up. Rick reveals to them what Dr. Jenner had told him: everyone is a carrier of the condition that makes people into zombies. Members of the group are very upset at the revelation and the fact that Rick withheld the information from them.
After explaining his reasons, Rick walks alone to the side of the road. Lori follows and offers some support. Rick tells her about what happened to Shane, how he killed him and how Carl killed the zombified Shane. Lori seems horrified and won't even let Rick touch her.
After a whole day of running and avoiding Walker, Andrea is exhausted. Out of ammo, she ends up having to smash some of their heads in with the handle of her gun. Eventually she gets knocked down by one and loses her only weapon. With a smooth motion, the Walker that has Andrea pinned down loses it's head. Moving the body off of her, Andrea sees a hooded figure holding a katanna sword in one hand and a chain leashing two armless Walkers in the other hand.
At the makeshift campsite, the group is trying to figure out what to do. Some of Herschel's people want to leave and fend for themselves. Carol even openly questions Rick's abilities with Daryl. Both Herschel and Daryl seems to support Rick howevere. Rick grows angry thought and tells them if thats what they want to leave right now. He is sick of trying to keep everyone together and always beingquestioned forthat. During his tirade, Rick reveals that he killed Shane himself because of him constantly badgering him and the danger he was to the group. Carl breaks down and cries in his mother's arms while the others have various facial reactions come across their faces.
Rick declares that he is in charge now and that is the way it has to be. He goes on by saying that their has to be a place for them, not only to survive but live. Someplace that can be fortified and protected. The image pans from the group's small campsite and rises. In the distance a massive structure can be seen; it's a prison.