Andrea gets bitten by a turned Milton who was stabbed by the Governor. When her rescuers arrive just a bit too late, they hand her a gun, lock her in the room and Michonne watches as Andrea blows her head off.
During the battle for the prison, the survivors ambush the Woodbury residents and send them running. One of the kids from the fight strayed away and ran into Carl. While trying to surrender Carl puts a cap in his dome like he was just killing another zombie. Hershel is displeased and tells Rick. Rick confronts Carl and he's like "so what dad, I shot a kid, big deal."
The Governor goes completely psycho and slaughters his Woodbury "army" because they retreated from a losing fight. Some nobody named Karen manages to survive the Governor-gun-down by hiding under someone's dead body. The Governor and two of his thugs drive off into the sunset.
Karen and the trio of Rick, Daryl, and Michonne show up at Woodbury with Tyreese on guard. Karen negotiates a ceasefire. They come in, pack up the rest of the Woodbury residents and move to the prison.
TL;DR Andrea finally dies and Carl is a sociopath.