A number of plot points will inevitably be revealed in the course of these writings. My intent is to review this program from the perspective of the Doomer / Prepper / Survivalist community, but, to do that effectively, some things have to be explained in greater detail than I might normally prefer in a review. As a result, spoilers will follow. You have been warned.
The episode opens with Shane, apparently safe back at the Greene's farmhouse. As you'll recall, we last saw him with Otis at the abandoned high school/FEMA shelter in a situation that could be described as anything but safe. He is shaving his head with a very intense look on his face as he stares at himself in the steam-fogged mirror. The next scene flashed back to the present (scary, crew-cut Shane was apparently a glimpse of what will happen later) where Shane and Otis are being chased down the hallways of the abandoned high school. Back at the farm, Rick tries to reassure Lori that Shane will come through with what they need to save Carl.
At the highway, Daryl and Andrea set-out before first light to search for poor lost Sophia. Not much happens, other than a chance for the viewer to better get to know both characters. The only thing I found important from a Doomer / Prepper / Survivalist standpoint was their reasoning for going out before sunrise; Daryl was hoping Sophia might see the light from their flashlights in the dark forest, creating a beacon for her. Not a bad idea.
Otis and Shane are both injured as they try to work together to escape and get back to the others, making it even more difficult to outrun the Walkers. Later in the episode, Shane will make a fateful and controversial decision that solidifies him as being simultaneously the most pragmatic as well as probably the most hated and feared character on the show throughout the first 2 seasons. Other than the mindless Walkers, he is the closest thing to a villain that this show has with Merle in the wind and Abusive Ed (that's his new nickname) partially eaten by Walkers and buried on the ridge above the flooded quarry (presumably). The thing about Shane is that he's not evil or even, necessarily, selfish. He does what he believes has to be done, ethics be damned, to ensure the safety of those he cares about. In the end, Rick is a better leader and a better person, but you just can't shake the feeling that Shane is the one who -- if you had to choose between the two -- would probably keep you alive longer. I won't reveal exactly what happens here; you need to see it live to truly appreciate the drama.
Back at the farm, Hershel is worried they may have to go on with the operation without the respirator, even though Carl likely won't survive. He's quickly running out of time, though, before he will die anyway if they keep waiting. Lori wonders if him dying now would be for the better, believing that the world they are all surviving in now is not a world for children. Even if he survives, she says, it will just be to spend the rest of his life hungry and afraid. Rick eventually helps her see some hope in a hopeless world, or, rather, he makes her see that Carl himself (and the fact that, as a child, he still has his sense of wonder) is himself a source of hope. Just about to chance the operation without the respirator, however, Shane makes it back with everything they need, and the surgery is a success.
The episode ends back where it began in the bathroom with Shane, his head shaved, looking at himself in the mirror as before. Only this time the viewer understands what is going through his mind.