For the citizens of Lumber City, Georgia, the epidemic brought with it government assistance. The Colonel and his men quarantine the City, closing down roads, and taking all survivors to Mathew Airfield – but an incident instigated a riot and the military complex became the casualty of a rather gruesome rebellion. Many lives were lost, and few people escaped. Reestablishing himself; the Colonel used religious propaganda and used fear to assert authority and regain controlled of the military base. The citizens now call him The Preacher. In the short time since the loss of his son the Colonel turned from solider to an extremist fundamentalist who sees himself as the magistrate of purgatory, and is willing to resort to the most extreme of measures to achieve his ultimate goal, revenge. While the Preacher enslaved those who would listen with religion, his second in command (Chris) enslaved the rest by rationing food, water, raping and beating women and feeding those too weak to fight to the walking dead.
The Preacher ordered Chris to bring forth his son's killer not knowing it was Chris who refused his son medical attention and let him bleed to death. Chris accused Cuca, the victim’s girlfriend, a woman he has been obsessed with and tried to rape twice. Mousy, a witness, informed Caroline of the truth and after some investigating she realized Cuca was innocent and helped her escape. Caroline stayed behind to lead the militia with the ultimate goal of eliminating Chris and the Preacher. Scavenging in the city Cuca meets other survivors and warns them about the airbase. The group tries to find a way out of the city, among them is John, a man with military expertise, he volunteers to scout ahead. But he gets captured by Chris's military goons and is brought to the airbase as a prisoner. Fearing recapture, Cuca decides to sacrifice John and leads the group to her hiding place. The Preacher disappointed with Chris’s inability to track down Cuca strips him of rank and kicks him out of the airbase – with the ultimatum that he can only return if he finds Cuca.
Cuca and the group are attacked by scavengers, Elijah gets shot on the foot, and Sam, who is somewhat unstable, shoots down the scavengers in a rage - the crossfire attracts nearby walkers and some members get kill. One of the women in the group is bitten and infected during the incident - Cuca decides to shoot her point blank in the head. Her decision creates a conflict between her and CJ, the dead woman's best friend. Cuca and Billy help Elijah with his wound and Sam disappears. Chris uses John's walkie-talkie to fish out the group. CJ answered. Chris extracts information from CJ and is delighted to learn Cuca is with them, he baits CJ into believing John is injured and needs their help. CJ gilts Cuca into forming a rescue party for John. She and CJ set out to find John. As they are leaving Sam returns and she brings him up to date, charging him with looking after the others while they go look for John. While driving on the road a sniper shoots CJ in the head killing him instantly, followed by shots to the tires on Cuca's truck causing the vehicle to spin out of control and flip over. Surprisingly Cuca is still alive. She get's pull out of the vehicle by no other than Chris himself.
Back at the airbase the arrival of Captain Shelton and Lt. Seth brings some hope. Mousy introduces two young woman to them, Adele and Firelily, under the pretense of showing them a good time, but the girls are actually militia spies, their job was to determine if Seth and Shelton can be trusted to join the militia. Shelton meets Adele, and she tells him about the horrors the citizens suffered at the airbase, including the raping of woman. Shelton feels sympathy for the woman and promises to help. The woman informs him that Mousy will be bringing him to meet Caroline - the leader of the militia. Seth on the other hand takes advantage of the situation presented to him and beds Firelily, even after she informed him that she didn't want to have sex with him but that she had no choice in order to avoid a worst fate. By then the rumors of Chris's expulsion from the base have spread. Shelton meets the Preacher and he is promoted to second in command. Shelton is surprised by the promotion, but having already become aware of the ill going on by Chris he is willing to take his place and bring some order. Shelton meets Caroline and the two come to an agreement, she will follow his lead when it comes to dealing with the Preacher and in return he will help train the citizens (the militia) to fend for themselves.
Sarah Brown comes across Mathew Airfield’s fence while passing through Lumber City. Whit her is her little girl who is in some state of shock, and withdrawn, a result of the hell they've been through since the outbreak. She stumbles into walkers roaming the area and is rescued by a soldier who debates weather he should let her take her chances on her own, or allow her to come inside the airbase - what he considers a much worst place to be. Pitying them he decides to take Sarah straight to Caroline. The two woman meet and Caroline immediately tries to get Sarah to join her cause which only alerted Sarah to become suspicious of Caroline and question what she's stepped into. She has every intention of leaving but then she sees her daughter playing with other kids, and for the first time in a long time she seems happy, normal. She decides to stay a little longer. Sarah finds the chapel where she morns the loss of her son. She meets the Preacher who comforts her and the two seem to bond over the fact that they've both recently lost a son.
Sam, Elijah and Billy are worried when Cuca doesn’t return. Billy is mentally spent; he can't deal with the hellish place the world has become. He feels lost and depress. Elijah gives Billy a gun while they separate scavenging through an empty house for supplies. Billy locks himself in the bathroom and shoots himself in the head. Sam can't help but to blame himself from the incident, Elijah helps him cope. The boys meet Mina, a young girl on a motorcycle. Together they decide to take their chances and see the airbase where they suspect they will find Cuca and John. Sam confesses to Elijah that he has decided he will separate from the group as soon as they find the airbase. Elijah tries to understand Sam’s reasons and starts to realize Sam is mentally unstable.
Cuca wakes up in the basement of a house, she is tide up and gagged and she's been beaten and raped. She hears Chris talking to another man. The man has brought supplies and Chris tells the man to return in four days. The man is Yusaf - he gets in the military truck and somewhere near the airbase he stops to take a dump. Annabeth, who on the run for some time sees the parked truck, believed it has been abandon jumps in the box to look for supplies. She is startled when the truck's engine roars on and it starts moving. Unable to jump out she hides. Eventually the truck stops and Annabeth finds herself inside the military base.
The Preacher calls an assembly where he informs the citizens he's gotten rid of Chris forever. He blames Chris for everything and announced his replacement. He publicly calls Caroline forward and declares a truce. He declares anyone who wants to leave will be allowed without problems. But then he calls Sarah forward and recounts her tale of survivor in a world that has changed forever, a world that forced her to kill her little boy when he became infected and turned into a walker. He uses Sarah’s story to put fear in the mind of all the parents present. Surprisingly nobody leaves.
Shelton makes a speech with promises to bring to justice those who have committed crimes against the citizens. Firelily doesn't trust Shelton and decides to test his loyalty by accusing Seth of raping her. Shelton is shocked by the accusation and promised to investigate. The assembly is followed by a feast - but Shelton, Caroline, Firelily and John (who had been released from the prison and as it turned out had served with Shelton and Seth in Iraq) meet in Chris's former office to investigate the accusation. The meeting is interrupted by a visit from the Preacher, who pulls Shelton to the side to inform him that Chris is still communicating with his men and that they have been providing supplies to him. At this time the Preacher overhears John talking to Caroline about the group of people he met and the girl name Cuca - he hears when Caroline tells John that she was the one who helped Cuca escape.
The Preacher is outraged. He orders Shelton to arrest Caroline and demands that John tell him where Cuca is, but John refuses and lies, telling the Preacher Cuca is dead. The Preacher doesn't believe him. He attacks John and Shelton intervenes. The Preacher gets a visit by the apparition of his son that leads him to the cellars where he has been keeping the infected remains of all the soldiers that died during the first riot, including his son. John, decided for himself to bring an end once and for all to the Preacher and followed him. He witnessed when the Preacher let the walkers lose. John gets attacked by a walker and bitten.
The walkers spread through the cellars and soon pushed their way up into the woman's cellblock, others slipped into the children's block, and in matter of seconds the entire base was attacked by walkers. Purgatory had begun, and Chris's men were prepared for this day. They quickly took sniper positions on the roofs, shooting down military personnel, and any citizen weathered armed or not. They ambushed the men's cellblock with gasoline grenades that quickly spread like wildfire and locked the doors from the outside trapping those inside to be burned by the fire. They took over the storage facility and killed indiscriminately anyone who got close. The guards at the gates were killed and the gates opened and anyone who tried to get into a vehicle to escape got shot down. The Preacher finds Sarah’s little girl and takes her into tower A to protect her from the riot.