Kevin McFarland reviews the latest episode of AMC's lumbering, flesh-chomping, zombie-infested near future. More episode recaps in Boing Boing's "The Walking Dead" archives.

The Walking Dead comic series creator Robert Kirkman wrote this week's episode, "Isolation," and that bit of information colored the one overwhelming action moment. As Darryl, Michonne, Tyreese, and Bob Stookey (Lawrence Gilliard Jr., getting the screen time with Cutty he didn't have on The Wire) journey to a veterinary college 50 miles away in search of antibiotics, they encounter a massive array of walkers blocking the road as far as they can see. Like the mass of undead that descended upon Herschel's farm, a chain reaction started by a helicopter flyover, this is a seemingly insurmountable wave making its way slowly but surely toward the already weakened prison defences.

Kirkman's comic perpetually offers glimmers of hope, of survival to fight another day, but not permanent resolution. By and large, teasing something positive, a solution to a major or minor problem, hints at a positive outcome before thudding back to earth in misery. The trajectory of hope in the world of The Walking Dead recalls Louis CK's attitude toward optimism: "Why the fuck would anything nice ever happen? What are you, stupid?"

If medicine cures the outbreak of disease in the prison, it doesn't solve the larger problem: a massive horde of walkers moving down the highway, forcing the fastest car the survivors have off the road. They are coming, there are always more of them, and they relentlessly chip away at every single character's chances of survival.

Even in a potential safe haven, the cruel truth is that the surviving Americans aren't equipped to thrive for longer than what amount to a brief reprieve from the new technological paradigm. They have been plunged into a world where zombies roam the earth biting, infecting, and killing, but also where medical supplies are increasingly scarce, living conditions are temporary and thus relatively unsanitary. Humans can no longer defend against pathogens previously taken for granted, which is why influenza is such an unexpected enemy. It's like the Oregon Trail, but anyone who dies of dysentery may rise up and eat the rest of the wagon party.

Tyreese is this week's example of the fallen hero. Put simply, Tyreese is in a bad place. The woman he grew to care about greatly in a short period of time got sick with a deadly virus and was murdered before turning into a walker—getting medicine in time was a tenuous prospect and nobody has yet staved off the illness naturally. And now his sister Sasha is also sick, confined to the same isolated block as the rest of the infected, including Glenn, which, yikes, that's a doozy, considering how safe the major characters have been since Andrea at the end of last season.

There are very few things I know to be true about The Walking Dead, but keeping Glenn alive is a universal truth at this point. I'm aware of a few future events in the comics, and I just have to say that teasing the possibility of a negative fate for Glenn right now would be just about the worst decision the show could make. It's not going to happen because of how beloved the character is and where the show is in the overall story it's trying to tell, but this is one of the few times when it's fairly obvious that teasing the death of a major character has to be a red herring. The fact that Glenn gets sick tells me that either some people recover from the illness, or that the mission to obtain medicine will be successful even if it's drawn out over several episodes.

But now back to berserker Tyreese on the hunt. He's so angry about Karen that he flies out of control, echoing Rick last year, lashing out and starting a fight with Rick. Tyreese wants to be the arbiter of justice, but in the prison, there is a council, a way of doing things, an attempt to return to order even in the bleakest situations. Of all the characters in various isolated locations, Beth tending to Judith is the most poignant about Tyreese's inconsolable rage. Beth repeats her father's command, that they all have jobs to do, and they're not allowed to dwell on sad feelings, they just have to be happy for the time everyone shared together no matter what happens. But try as she might, Beth doesn't really believe this to her core. When her boyfriend died, she held nerves of steel when talking to Darryl, but when it comes to her father and Maggie's long-standing relationship, Beth cracks, revealing that everyone is still affected by the possible tragedies that could befall the survivors. The paradisiacal life they've been leading since the confrontation with the Governor only amplifies the low extremes.

Tyreese, on the other hand, got too involved too fast, and as a result the one-two punch of his lover and possibly his sister makes him such a liability that he waits in a car too long when fleeing from walkers, and randomly decides to take his anger out in a suicidal and sacrificial display. Somehow he survives after massacring the zombies and reunited with Darryl, Michonne, and Bob, but now they're on foot the rest of the way.

Herschel gets the significant speech of the episode, to Maggie and Rick as he prepares elderberry tea to stave off fever in the hopes of buying more time for the antibiotics to arrive. It's a stirring, purpose-affirming way to look at a tragic scenario, and the best way to approach life when survival for a sustained period of time appears impossible. Everything is dangerous, from stepping outside to drinking water to breathing, and in one of those wise moments for Herschel, he outlines the only choice they really have is risking their lives for something meaningful, like sustaining the infected for a few hours longer.

Carl accompanies Herschel while foraging for the berries, where the elder man addresses Carl's returned gun—obliquely bringing up Carl's actions at the end of last season—and prevents Carl from shooting two walkers, one trapped by a fallen branch and another with a large trap around one foot. The last time Carl saw a walker and then let it do, Dale met an untimely end. But perhaps this scene isn't the same kind of foreshadowing, how immaturity can lead indirectly to death. It shows the premium Herschel places on the peace of the natural surroundings, how he attempts to avoid whatever violence he can to maintain the happy illusion for as long as possible.

The walkers crash against the prison fence every day, and now the living population dwindles in the prison. The survivors can't stay forever, that is growing increasingly clear. But the illness delays the decision, and it's clear that the resolution will not be a quick one. The expedition to obtain antibiotics will take a while, if it turns out to be successful, and Rick will have more time to contemplate Herschel's continuing insistence that he participate in council meetings. These first eight episodes seem to be concerned with what happens to the group when they're beset not just by the big problems crashing down from the outside, but also being torn apart from within.

Which leaves the final revelation: Carol killed Karen and David, dragged their bodies out of the prison and lit them on fire. It's certainly a possibility, given her rise to stalwart co-leader teaching even the smallest children to handle knives and defend against walkers. She is no longer the meek housewife resigned to the cooking and laundry. But Rick arrives at the confrontation a bit too neatly. He extrapolates from her attempt to clear the water lines alone, and asks if she'd do anything to protect the people in the prison. Then he jumps to the big question, and I'm not sure the episode lays enough groundwork.

Retroactively, it does color her reactions throughout the episode, from putting a young girl in the quarantine cellblock to agreeing to check on Sasha while Tyreese joins the antibiotic expedition. Instead of appearing like an overly burdened woman on the verge of cracking because everyone comes to her to unload emotional trauma, she's overcome with the guilt over doing what she believes is necessary to protect those who may survive a bit longer. But what did she do: murder two sick people with a chance to recover, or prematurely take action against the inevitable? Whichever side Rick comes down on determines how he will choose to deal with it should the convoy return. Carol didn't stem the spread of disease, risked her health in the process, and is now a threat to kill again. Two council members sit in the quarantined cell block, along with at least one child, and Carol has come a long way from timid wife and mother to take dangerous action into her own hands.

Extra Brains

• The woman pleading with Carol that she just has allergies isn't convincing anyone with her lame excuses.

• The doctor should really know to cough into his elbow or cover his mouth in some way. That was just an inconsiderate way to ensure that Herschel was exposed just in case he had any chance of staying healthy.

• The scene of Melissa McBride reacting to Tyreese's request is one of her best in the entire series. She goes through an entire range of emotions, and then once the final twist has been revealed, those emotions take on a totally different significance. Just a great performance from a character that means far more to the group than she did at the start.

More episode recaps in Boing Boing's "The Walking Dead" archives.