Months have apparently passed and the prison has been transformed into a farming community. Rick is staying put, tilling the fields, checking traps and keeping an eye on Carl. Darryl is much loved and leads the major runs for supplies. Michonne returns from her search for the Governor and goes on the run. New boy Bob goes along too but gets trapped under a shelf full of booze. Above the store a crashed helicopter has drawn Walkers and weakened the roof. The Walkers begin tumbling down and Zach is killed. Rick comes across a dishevelled woman (Clara) who takes him to meet her husband. However he is dead and she has given up on life claiming she can’t come back from the things she’s done. Back at the prison a young boy named Patrick dies in the showers.
Patrick attacks his cell block and others begin to turn. The Walkers are put down and Carol encourages Lizzy and her sister to kill their dying father. The belief is that an infection may have spread from the animals. Rick is shaken by being called back into action but is soon taking the lead. As Walkers begin pulling down one side of fence he kills the pigs to draw away the threat. An injured Michonne weaps when she has to hold baby Judith. Karen is quarantined along with another symptomatic resident and Tyreese finds them both dead.
Rick and Tyreese come to blows over the burnt bodies. The Council isolate the young and the infected. Darryl, Michonne, Bob and Tyreese head out to find medicine but come across a massive swarm of Walkers. Carol tries to fix the water line alone and Rick has to bail her out. Hershel risks infection by taking food to the sick.
Rick and Carol go searching for food and medicine. They run into a young couple who Carol encourages to help them. One of them is killed and Rick tells Carol she isn't welcome at the prison anymore. Meanwhile Tyreese struggles to get over his grief and Bob admits his alcoholism to Darryl. The group grab a van and make it to the veterinary college. They get the meds they need but Bob again reaches for a bottle.
Hershel tries to keep hope alive on Death Row. However when three people turn in a short space of time he is pushed to his limits. Maggie comes running in to help but Rick has to stay outside and tend to the sagging fence. He asks Carl to help him but the fence collapses and they are forced to gun down a whole crowd of Walkers.
We follow Philip as he's abandoned by Martinez and stumbles across a family living in an apartment building. He slowly wins their trust and comes to care about them. Particularly mother Lily and daughter Megan. After Lily's father dies they decide to move on. They are attacked by a group of Walkers but Martinez rescues them.
Martinez takes the Governor in but is soon regretting it as he is thrown into his own Walker pit. The Governor is dismayed to see the standard of leadership left at the camp and considers leaving. However he soon realises that he must take charge again.
The Governor makes his pitch to his people and they agree to go to war. Lily stays behind and Megan is bitten by a Walker. The Governor threatens to hurt Hershel and Michonne if Rick won't leave. Rick offers to take the Governor's people in but Hershel loses his head to make certain that won't happen. The guns begin to fire and Michonne escapes and kills the Governor. Darryl leads the defence of the prison as most of the survivors escape on a bus. Several groups are separated though as Walkers march into the prison.
Rick and Carl bicker and stagger to a house for the night. Next day Rick is coma like as he recovers from the stress. Carl goes wandering on his own looking for more food. Meanwhile Michonne is hanuted by memories as she decides whether to walk with the dead or the living.
Daryl and Beth pick up the trail of some of the children but find Walkers devouring their bodies. Tyreese is still alive though caring for Judith, Lizzie and Mika. The stress is getting to him though when Carol appears. Sasha, Bob and Maggie find the bus but its inhabitants all turned. Glenn is back at the prison and prepares to escape. He bumps into Tara and pushes her to help him.
Michonne and Carl go out searching for supplies. They share their pain of lost family. Rick takes a nap but wakes up to find the house is being raided by another group. He hides nervously under the bed and eventually has to kill one of them. Meanwhile Glenn wakes up on a truck headed for Washington and insists on going back for Maggie. Abraham introduces himelf and Rosita and says they are taking care of Eugene because he knows how to save the world. Glenn prevails though and the group march back toward the prison.
Darryl and Beth continue to survive together. Beth wants to have her first drink and they break into a country club. Darryl isn't happy with their drink choices and takes Beth to a still. They drink moon shine and talk about their feelings.
Maggie finds the Terminus map and insists on following it. Bob agrees but Sasha would rather find a secure location to make home. Maggie leaves them behind so that they won't feel burdened by her mission. Bob insists on following after her. Meanwhile Darryl and Beth come across a funeral parlour and begin to play house. Soon a host of Walkers overrun the place and Beth is seemingly kidnapped. Darryl tries to follow but eventually collapses in despair before being discovered by the gang who Rick recently escaped.
Glenn finds the messages from Maggie and pushed on into a railway tunnel with Tara. Abraham, Rosita and Eugene leave them to it but Eugene insists on picking them up at the other end. Joe teaches Darryl the rules of their group.
Rick, Carl and Michonne get close to Terminus. Joe’s crew catch up with them and threaten to rape and slaughter. Darryl offers himself as sacrifice. Rick bites Joe’s throat out and kills their whole crew. Carl feels distant from his father as Michonne tries to reassure him. They approach Terminus with caution and sneak up on a bunch of people broadcasting and making maps. However Rick soon recognises his friends’ stuff and pulls out his gun. The four of them are ushered into a train car where they find Glenn’s group.