The group has been on the run moving from house to house through rural Georgia for the last eight months. The group has now become more proficient with firearms, Daniel is now seen by everyone as the leader of the group, and Cristina's pregnancy is advancing.
Moving as a cohesive unit, Daniel, Fábio, Gonçalo, and Bruno breach a house, eliminate the walkers inside, and search the place to make sure it's safe for the group to camp out there. After the search is over, the others enter the house. Everyone starts to settle until Fábio looks out of the window and notices a group of walkers approaching. Everyone runs to the cars and they drive off.
The cars stop on a highway to discuss where they are headed. They open a map and discuss how they have been moving in circles for months, trying to escape the herd that passed on the Greene Family Farm. Kiko and a few others head to gather some water, while Daniel and Gonçalo go hunting. While hunting, they walk down a railroad, and observe a prison full of walkers. They've found shelter.
Fábio starts to cut the fence so the group can get within the prison exterior. Caramelo and Alexis then tie back the fence so no walkers can enter behind them. They start to run, stopping at the prison gates. Daniel says someone has to get past the prison yard full of walkers to close the gate on the other side, Kiko offers, and Daniel decides that he will go with him. Daniel tells Cassandra, Inês, Diana, Hershel, Cristiana, and Bruno to shoot walkers from the guard towers. Daniel straps a rifle to his back and is handed some chains, Mariana mans the fence. Daniel and Kiko head towards the gate. They kills a few walkers on their way there and then secure the gates. They then enter a tower and with help from the rest of the group, shoot the remaining walkers in the yard to secure it.
Having taken the yard, the group sit down for a fireside meal and, at Hershel's request, Beth and Maggie sing an old Irish drinking song, Cassandra and Cristina later join in and sing along. Caramelo flirts with Beth after she sings, but Hershel pushes him away, while Ruth and Fábio share an awkward look. Gonçalo is keeping watch at the main gate and Sophia starts flirting with him. Daniel makes plans to take the prison entirely, convincing the group that it'd be safer on the inside. He tells them how there will be food, weapons, and medicine in the prison, and that, "these [walkers] assholes don't stand a chance".
The next day, Daniel, Gonçalo, Cristiana, Kiko and Maggie take the interior while the rest serve as a distraction. Everything seems to be going well until they run into walkers wearing riot gear. However, they're taken out and the group advances into the prison. They enter Cell Block C, take out the few remaining walkers lurking inside, and find it to be secure. As everyone starts to set up in different cells, Daniel starts to show an interest in Beth, asking her what was going on between her and Caramelo, but she assures him that there's nothing between them, then Daniel goes off to find his own cell.
Inês and Diana look at each other, smiling for finally finding a safe place to live. Mariana and Cristiana also seem to get comfortable in their own cell. Mariana tells Cristiana that she's happy that they found the prison and that she thinks they can build a better life now, telling Cristiana that she's also happy Cristiana's fine, as well as Inês, Diana and Daniel, because she sees them as her family, even Bruno. Bruno and Daniel get a cell for them. Daniel asks what he thinks about the prison and Bruno tells him that it's not as good as their former house but atleast is safe. Alexis looks at his surroundings entering in a cell with Gonçalo, "So we're prison buddies now? Alexis tells Gonçalo, joking. Leandra shares her hope with Cassandra, telling her that she believes things will get better now.
Cristina confides in Hershel that she fears the baby might be stillborn, and that it might be born a walker. Nonetheless she makes Hershel promise that if the baby is a stillborn or if she and the baby both die in childbirth not to hesitate, and put them both down. Cristina decides to stay in the cell block near Hershel's. Kiko, not having a cell partner, asks Maggie, who was settling in a cell for herself, if he could stay with her. Maggie accepts it, but warns him that if he tries anything, she'll kick him out, making him promise.
The group finds a plethora of weapons and suit up to further explore the prison. Daniel, Gonçalo, Fábio, Kiko, Maggie, and Hershel move deeper into the interior. All seems quiet at first, but suddenly they run into several groups of walkers. In the darkness and confusion, Fábio and Maggie get separated from the group. When it's finally safe to venture back out, Hershel tries to find the two but is bitten on his calf by a walker that only appeared to be dead. The group then reunites and assists Hershel in getting out of the corridor. They take refuge in the cafeteria, where Daniel, in an attempt to save Hershel, amputates his leg, causing him to go into shock and pass out from the ensuing blood loss. Then, 3 figures appear in the adjacent room. Gonçalo prepares to fire, but realizes they are not walkers but are actually more survivors living in the prison. He shines his flashlight in one of the prisoner's faces, to which one of the prisoners exclaims, "Holy shit!"
- First appearance of Tomas.
- First appearance of Andrew.
- First appearance of Big Tiny.
- Numerous changes occur within the main cast.
- Paquete is no longer listed as main cast, having been written off the TV Series in Season 2.
- Sophia and Caramelo, are both added to the main cast. the were both promoted to a TV Series regular after being a guest star in Season 1 and 2.
- Ruth, Fábio, Alexis, and Fábio were promoted to guest stars, after being Co-Stars in the previous seasons.
- Johanne doesn't appear in this episode.
- Like Allen in the Comic Series, the leg of Hershel Greene was amputated after being bitten while stepping over a walker.
- In the Comic Series, the original intention was for Hershel to lose his leg instead of Allen.
- The name of the episode, "Seed," may refer to when Hershel suggests that they plant seeds to grow tomatoes, cucumbers, and soy beans within The Prison yards. It may also refer to the idea that they have begun planting their own 'seed' within The Prison, which will eventually provide a new life for them, or it may even be referring to Cristina's unborn baby.
- This episode's cover represents the moment when they are forced to leave the house.
- This is the first instance where Cassandra, Caramelo, Fábio, Alexis, Cristina, Fábio, Ruth, Leandra and Beth Greene are seen killing walkers.
- This is the first season premiere that isn't 90 minutes long.
- This episode begins with a close-up on a walker's eye. The season finale starts with a close-up on the Governor's eye.