Season finale time! We start off with a little bit of Shane backstory, showing him in Rick's hospital room just as all hell is breaking loose. In the hallways, soldiers are killing indiscriminately, walkers and humans alike. Shane tries to lift Rick from his bed but the comatose man is too heavy, plus he's hooked up to all these machines and Shane just doesn't know what to do. An explosion rocks the hospital, knocking out the power. Shane panics, putting his head to Rick's chest, and when he doesn't hear a heartbeat - which, how could he what with all the gunfire and screaming and whatnot going on around him - he apologizes to his friend and gets the hell out of there.
Back in the show's present, Edwin Jenner is the name of the doctor barricaded in the CDC building. He lets the band of survivors in, telling him that a blood test for each of them is the price of their admission, and warning them to bring in what belongings they have, for once the blast doors close behind them, they won't open again. A little later, the blood tests all having come back clean, Jenner treats the survivors to food, wine (much wine) and hot showers - and it's difficult to say what is enjoyed more.
At dinner, Shane kills everyone's buzz by asking Jenner why it is that he's the only one left. Jenner explains that the other CDC folks either left to be with their families or stayed for a while before killing themselves. He himself stayed to do what work he could. Afterwards, everyone is drunk in different ways: Andrea is despairing that nothing is left in the whole world; Rick is a little maudlin, thanking Jenner for saving their lives when he was losing hope; and Shane catches Lori alone, intending to plead his case but ultimately nearly raping her before she claws his face and chases him off.
The next morning everyone is hungover. Along with the aspirin, coffee and powdered eggs they ask Jenner if the CDC has come up with any answers. He shows them a scan of "Test Subject 19," an infected individual who volunteered to be hooked up to the CDC's computers so they could see just what happens. What happens is the brain dies from whatever agent - viral, bacterial, microbial, fungal, who knows - is transmitted by zombie bite, and then the agent restarts the brainstem only, so the walkers are not quite alive, just moving on instinct and reflex. The scan ends with a bullet through TS19's head. Everyone is stunned, moreso when Jenner tells them that the epidemic is global and there is really nothing left. Dale apologizes for asking yet another question, but wants to know what the big clock on the wall is counting down to - there's one hour left. Jenner says that's when the generators run out of fuel and "facility-wide decontamination" occurs.
Everyone scurries around for a while, trying to confirm that the building is in fact running out of fuel. When the clock hits 30 minutes, the laboratory doors close, locking Jenner and all the survivors in. Jenner, calmly, resignedly and just a little crazily, explains that the building is responding to the loss of the power grid, which were this situation to have happened in the event of a terrorist attack, the building will obliterate itself and all the nasty bugs the CDC has collected (weapons-grade smallpox, Ebola, etc.).
Much panic ensues until Rick convinces Jenner to let them out, to at least give them a chance at survival, grim as it may be. Jenner does, warning them that the topside doors are sealed and he can't do anything about that, and then he whispers something in Rick's ear. Everyone runs topside - everyone except Jacquie, who prefers an immediate, painless death to fighting anymore, and Andrea, who has simply given up in the wake of her sister's death. Dale tries to convince Andrea to come with him. When she refuses, he sits down beside her and says, fine, then, he'll stay here too because he cares about her and can't face life topside without her. She stares at him, horrified that he would give up his life for her like this.
Upstairs, nothing anyone does can break the safety glass ... until Carol hands Rick the grenade that she found in his clothes when she washed them for him. (Remember, he pocketed it when he was trapped in the tank.) He places it against the window and BOOM, the window shatters. They all run for their vehicles, offing a few lurching walkers as they do so, and are about to drive away when Dale and Andrea make their way out of the CDC building. Everyone ducks and covers as the building explodes massively; Dale and Andrea get into the RV; and they caravan away to fight zombies another day.
Still: where's Merle? He better show up in S2.
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