Just what we need: another group of survivors. Tyrese, Sasha, and a family of three fight their way through the woods and blunder into the prison's busted-ass rear entrance, but not without the mother sustaining a bite. Inside, Carl seems to be the temporary leader of what's left of the group. Hearing the screams from the bowels of the prison, he goes down, rescues the new group, and locks them up in the anteroom outside Cell Block C with food and water, and a recently dead comrade for them to take out. So things at the prison seem fairly well under control for now.
The Governor orders the execution of Glenn and Maggie to prevent Andrea from learning of their presence, but they don't go quietly. In fact, Maggie kills one of their captors, which buys them just enough time that Rick and his rescue team are able to save them from immediate death. But getting back out of town soon proves more difficult than getting in; the alarm has been raised and the group is going to have to shoot their way out. Daryl learns that Merle is responsible for Glenn's injuries and wants to see him, but agrees to be there for Rick on the way out.
Michonne has her own agenda, though, and while Rick and his people are working on their escape, she sneaks into the Governor's place and awaits his return. But before he gets home, Michonne discovers his creepy den, with the tanks full of heads and the walker-child locked up behind the grate. She's about to take her out when the Governor stops her. There's a hell of a fight which the Governor loses, along with an eye, but Michonne's delivery of the coup de grace is forestalled by the timely arrival of Andrea, who somehow has remained ignorant of the nature of the intrusion into Woodbury all this time.
Rick and his group fight do fight their way out, but at a cost; Rick suffers a Shane-flashback, Oscar is killed, and Daryl stays behind to provide them with covering fire and is unable to make his escape. Michonne reunites with Rick, Glenn, and Maggie outside the walls and tells Rick he'll need her help, whether he chooses to get the injured Glenn back to the prison or return for Daryl. And the Governor assembles the townspeople and makes a speech all about the terrorists who attacked them, naming Merle as one of them (probably because he now knows Merle lied to him about having killed Michonne) and displaying Daryl as a prisoner in the arena. But whatever he's got planned for them, it's going to have to wait until February.
It's a foggy morning in the Georgia wilderness, and distant screams echo through the woods. A walker plods toward the sound, until a large man (The Wire's Chad Coleman) jumps out from behind a tree and brains it with a pickaxe, as well as the other one following it. He runs toward the sound of a rushing river and almost into a shovel swung by a human woman, but they know each other from another group that's apparently been separated from each other. The man, Tyrese, tells her he spotted a tower not far off, and they run back to collect the several other members of their group from a pitched battle with more zombies. But they don't make it clear without another woman in the group getting bitten on the arm. They drag her along and, after some debate, all the way inside a torn chain link fence and through a shattered brick wall... which leads inside the prison. That place is getting more crowded all the time.
Andrea stands in front of the Governor's mirror and looks at an old family photo of his, possibly noticing the resemblance between herself and the late Mrs. Governor. When the man himself enters the room, Andrea tells him that she's going to help Milton cremate Mr. Coleman this evening, and waxes schmoopy about how Woodbury is all about people helping people. The Governor lets her go without bothering to straighten her out on that score.
After she's gone, the Governor sits in his den with the zombie-heads in fish tanks and opens the grate in one wall. He turns on a boombox playing a lullaby and calls to his daughter, Penny, who, after some emitting some snarling noises, comes rushing out slavering with the bag over her head, brought up short by the chain around her neck. The Governor removes the bag and almost seems able to calm her down somewhat by singing along, but the walker-child's attention is focused on a bowl of bloody meat, much to the Governor's eventual frustration. Back on the girl's head goes the bag, back in the cell goes the girl. Maybe leave the bloody meat in the kitchen next time, Guv.
In the dungeon, Glenn has given Maggie his shirt, but there's still the dead walker in there and Glenn's face is still covered in blood, so it's not as homey in there as perhaps it could be. He wants to know what happened with the Governor, and she assures Glenn that he barely touched her. "All this time running from walkers, you forget what people do... look at what they did to you." There's no mirrors in here, Maggie. Try to keep up. They hold each other for a bit, and then Glenn painfully gets up and rips loose the walker's arm, then breaks its forearm wide open and hands the severed wrist with the jutting bones to Maggie, presumably for use as a weapon. What ever happened to giving a girl flowers?