Up at street level, everyone is taking guns, axes and chairs to the windows, to no avail. Carol reaches into her magic backpack and pulls out the grenade that Rick lifted from the tank. She found it in his uniform when he arrived at camp and she was doing laundry, and she stuffed it away. Instead of getting mad at her for stealing his shit, he looks relieved. Did Jenner not run any kind of security check on these people? A live grenade going off could have been catastrophic underground. I guess he figured that was going to happen anyway, but what if it had taken out Vai and the building couldn't shut itself down and all the viruses got out?
Anyway, no time to dwell on how she got the grenade in -- Rick puts it by the window, pulls the pin and runs away. Good thing it isn't the kind that you need to throw. Downstairs Dale says that Andrea wins. If she's staying, so is he. She doesn't want him here. Jacqui looks miffed that no one cared that much about her. Dale borrows Lori's bug eyes and says the matter is settled and he's staying. The rest of the gang get out and start taking down walkers. Yay! I forgot this was a zombie show for a minute. Just as the gang is about to drive off, Lori spots people coming out of the building. Inside with less than 20 seconds left, Jenner and Jacqui look at the street cameras and see that their "friends" got out. Not sure how Dale and Andrea got up those however many flights of stairs and outside and across the lawn in what seemed like it should have been about 30 seconds, but they did. Maybe once this is over they can try out for some sort of triathalon.
With 10 seconds remaining, Jenner and Jacqui hold hands, and Lori screams at everyone to get down, Andrea and Dale jump behind some sand bags for protection. Fireballs start streaming out the open window, and look like they spread across the better part of two blocks. Somehow this conveniently misses the camper and fails to set the sandbags on fire. Even though the building mostly imploded, I'm surprised they were out of the blast radius. Or that, at the very least there isn't black ash raining down on the little caravan as it drives away. Instead, the oxygen-burning fire just billows up into big old black clouds, while the fire rages on the building below. I'd say if it wasn't for the toxic fumes, that staying around there might be wise, as the blast would likely have killed off walkers or at the very least frightened them away. But then again, if this major blast that looks like it will burn for several hours didn't manage to reach the camper parked a block away, then maybe it didn't kill off that many zombies. So black smoke and Rick gets his chance for the future. Poor Jacqui. I wish someone had spent a moment of time trying to save her, because she seemed awesome. These people spent a whole day trying to keep almost-zombie Jim alive, but Jacqui doesn't deserve a passing thought. Sad.