By Kat Rosenfield

Last week, one poor fellow named Patrick unleashed the double whammy of suck upon the community: first he dropped dead of a highly infectious, incredibly deadly flu, and then he walked dead into a bunk and ate somebody's bowels. The result: many people bitten, many more infected, and no telling who will be next to die.

SPOILERS AHEAD.

With twelve people dead in last week's walker infestation, and the killer flu tearing its way through the remaining population, the graveyard in the prison yard is filling up fast — and they'll need to dig at least two more graves for the charred corpses of Karen and David, who were mysteriously murdered and then burned by persons unknown. Tyreese, who's still reeling from having discovered the bodies, undergoes some serious character development before the opening credits even roll: gone is the big cuddly love-muffin from the first two episodes, and in his place is a panting, furious madman who looks ready to rip someone's face off. When Rick tells him to calm down, it's all over. Fists fly, other fists fly back, and the grieving Tyreese ends up on the ground with a bloodied face — while Rick ends up with a crisis of conscience over having lost his shizz, again.

The next half hour or so is basically a montage of people falling ill: everyone who was on the block that was decimated by zombies last week has been infected, plus the doctor, Sasha, Glenn, and Lizzie (the girl who couldn't knife her dad in "Infected".) With people coughing, sweating, and arbitrarily spraying blood from various orifices, the council decides to keep the sick people isolated on a single cell-block, and to put the vulnerable kids into quarantine in a separate building. Things aren't looking good, but as Beth says to Maggie, "We don't get to get upset."

While a group prepares to go out in search of elusive antibiotics (there's a veterinary college 50 miles away that the desperate survivors of the zombie apocalypse might have forgotten to ransack) Hershel is caught by Carl making a secret, sneak trip to the forest. The ensuing confrontation is like watching a ponytailed amputee Santa Claus facing off against the world's smallest serial killing cowboy — basically, weird — and Hershel reluctantly lets Carl come along, though he's obviously nervous about giving the trigger-happy tween a chance to use his gun. But when they come across two walkers in the woods, Carl obeys orders and doesn't shoot. So… progress?

Meanwhile, Tyreese joins Daryl, Michonne, and Bob Stookey as they ready the car for the trip to the veterinary school. (Looks like "The Walking Dead" has heard all the jokes about its dismal track record for keeping its non-whites alive and is actually now just messing with us; prior to now, sending three black characters into zombie-infested territory would have been a clear signal that someone was about to die.) Daryl informs Michonne that he knows she's been looking for the Governor, but needs to accept that the trail has gone cold — thanks for the exposition, Daryl! — and then there's a brief moment of excitement when he turns on the radio and there's a human voice briefly audible between the bursts of static. What was it saying? We may never know: a moment later, the car skids to a stop as the camera rises up and pans over the veritable horde of walkers that stands between the travelers and their destination. It's our heroes' cue to pile out of the car and start hacking/slicing/shooting their way to safety, but Tyreese isn't moving… and then, Tyreese is moving, and more specifically, he's cracking open the skulls of zombie after zombie with a hammer, screaming with grief and rage. The group is forced to leave him behind (at which point we were practically apoplectic, because OH NO THEY DID NOT JUST LEAVE TYREESE TO DIE OFF-SCREEN), but not to worry: he catches up to them later, covered in brain-splatter and looking thoroughly worn out.

And back at the prison, we've got two men on a mission: Hershel is bringing the natural flu remedy he found in the woods to the folks in the sick bay, and Rick is doing a little detective work out in the yard where the burned corpses were found. A handprint on the door seems to give him pause — and we cut to Carol, who's slipped out beyond the fence to clear the clogged hose that's stopped their water supply. She manages to fix the problem, but not without drawing the attention of some hungry walker; fortunately, Rick shows up and helps her to cut her way through the undead to safety. And why? Oh, come on. You know why.

"Is there anything you wouldn't do for the people here?" he asks.

"No," she says.

"Did you kill Karen and David?" he asks.

And Carol, cool as anything, says, "Yes."

So, mystery solved: Carol the mercenary sweetheart murdered and incinerated Karen and David in the hopes of containing the infection — and she doesn't seem particularly sorry, either.

Was Carol right to do what she did? Let us know in the comments below or hit us up on Twitter!