The unknown virus continues to spread, killing more people and infecting others, including Sasha, Glenn, and Lizzie. Tyreese is furious about Karen's death, and attacks Daryl and Rick in frustration, causing the latter to fight back. Hershel suggests that the group search a nearby veterinary college to find medication to help the infected. He also decides that the children, including Carl, must be separated from the other survivors, as they are more vulnerable to the disease. Hershel leaves the prison enclosure to search the woods for elderberries and runs into Carl, who insists upon accompanying him. They encounter one slow-moving and another immobilized walker during their trip, and Carl prepares to shoot them, but Hershel discourages him, advising that's unnecessary. Maggie cries about Glenn's illness, but Beth reminds her they all have jobs to do. Carol breaks down after offering condolences to Tyreese. Hershel decides to risk exposure by caring for the sick. He says they are always risking their lives, and the only thing they could do now is decide what they are risking it for. Daryl, Michonne, Bob, and Tyreese head to the veterinary college to retrieve medication, but on their way, they hear a voice on their radio speaking about "sanctuary". They suddenly encounter a massive herd of walkers, forcing them to abandon their vehicle, although a bitter Tyreese stays in the car. When he finally decides to get out, he is surrounded by the undead, forcing the remaining three to leave him and head into the woods. Tyreese miraculously survives the herd's attack and catches up with Daryl's group. After investigating Karen and David's murders, Rick confronts Carol, who admits she killed them.