'Sick' picks up right where The Walking Dead's third season premiere left off - the episode maintains the relentless pace of 'Seed' in a rather breathless opening sequence, which sees our survivors involved in a tense confrontation with a burly-looking set of prison inmates.
Of course, beyond that, 'Sick' can't hope to maintain the breakneck speed of the preceding episode, but this changing of gears is no bad thing, allowing the show a little breathing room without ever boring the viewer. Sure, we all love a bit of epic zombie gore, but when the character drama is this good, you don't miss it.
While the rest of the group deal with an injured Hershel (Scott Wilson), Daryl (Norman Reedus) and the refreshingly well-utilised T-Dog (IronE Singleton) face off against the inmates and the situation threatens to turn explosive until Rick interrupts, seemingly reassuming his old role as the group's voice of reason.
It becomes clear that the prison inmates have been locked away a long time and don't know how bad things are in the outside world. "There's no army, no government, no hospitals, no police - it's all gone," they learn, and their incarceration lends fresh eyes to the zombie apocalypse - their frenzied first attack on a single walker is a far cry from Rick and company's military operation when claiming the prison last week.
"This prison is ours," Rick growls, but the prisoners are adopting a finders-keepers / we-were-here-first mentality and the two teams eventually reach an uneasy compromise - our survivors will help the inmates to clear out a single prison block, where they'll remain, in exchange for food from their impressive stock. But this is The Walking Dead - when does a plan ever go smoothly?
Events take a dark turn when one of the inmates is bitten and their de facto leader mercilessly strikes him down in a frenzied and brutal attack. As the head inmate becomes more and more unpredictable, Rick - who up until now has mostly shown his new "ruthless" nature by looking a bit grim and snubbing his wife - decides to take action, killing his new nemesis with a machete blow to the head in a genuinely jaw-dropping moment.
More shocking still are the scenes that follow, in which Rick locks another fleeing inmate out of the prison, leaving him to the mercy of the walkers. Andrew Lincoln's ex-cop started out life as a clean-cut hero, but now - stalking a terrified man with bloodied weapon in hand - he more closely resembles the antagonist of a slasher movie. Is Rick spiralling out of control?
We certainly weren't confident that he wouldn't shoot two unarmed men - both on their knees - in a subsequent scene, and his behaviour is thrown into sharp contrast when it's Daryl - once the show's wild card - who's sympathising with their captives.
At least Rick and Lori's relationship - which initially remains colder than a walker's innards - seems to be on the mend a little. While the Grimes clan aren't exactly playing happy families, he certainly seems less openly resentful towards her than he did last week - that simple touch of the shoulder at episode's end, and Lori's emotive reaction to it, speak volumes.
The youngest member of the clan, Carl (Chandler Riggs), also continues to grow on us - sure, he still talks back to his mother but he also kills walkers and finds medical supplies for Hershel. The trouble-making little tyke of season two seems long gone.
Speaking of Hershel, he's in a bad way for most of the episode, with Glenn (Steven Yeun) keeping an uneasy eye on the old man knowing he might have to blow his brains out in front of his daughters at any moment.
Most of the Walking Dead series regulars got a good showing last week, but Glenn and Maggie received relatively little screen-time, so it's great to see 'Sick' shift focus a little onto the troubled couple as Hershel's fate hangs in the balance. Cohen in particular is excellent as she urges her unconscious father to "let go" and die a peaceful death.
Hershel does eventually give up the ghost, with Lori taking a big risk performing CPR on a man who could spring back to zombified life at any second. But her efforts work and he snaps back to life - still human - in a moment that we'll freely admit made us jump out of our skin. And so 'Sick' ends on the closest thing this show will ever get to a happy ending - it seems like Hershel is going to be okay, albeit missing one of his legs.
The Walking Dead continues to be thrilling, surprising, intriguing, stomach-churning drama - this season more than deserves the epic audience numbers it's drawing in. Next week, the MIA Michonne (Danai Gurira) and Andrea (Laurie Holden) return and a certain Governor (David Morrissey) makes his debut...