The second season continues with an episode told entirely in flashback, bookmarked at either end by a shell-shocked Shane shaving his head.

It’s a disturbing way to open, eerily reminiscent of Robert Carlyle in the classic Cracker episode, To Be A Somebody, and although it takes until the reprise of the scene at the end to establish what has led him to do it – and to see whether or not he’s flipped as far as Albie did – it’s clear that the mental tightrope he’s been walking for some time has narrowed to a thin piece of twine.

Shane’s struggle to cope with unrequited love and undead monsters has been superbly portrayed by Jon Bernthal, and his performance here as a kind of anti-hero with Post-Traumatic Stress Disorder is as good as any in the show so far.

In something as grim as The Walking Dead, there’s justifiably little in the way of cheeriness. However, there’s always time for a respite from the heavy principal storylines, and this week, Daryl and Andrea go for a moonlit stroll in the words in search of the still-missing Sophia and some respite from her grief-stricken mother.

After a homily from Merle’s brother about the time he went missing for nine days as a kid and ended up wiping his arse on poison ivy, they discover a living corpse hanging from a tree with a poem tacked to the bark beneath its kicking, mostly-eaten legs. From the content of the elegy – ‘Got bit / Fever hit / World gone to shit / May as well quit’ – it seems the walker might once have been Gerard Way of My Chemical Romance and yet Daryl is still inexplicably reluctant to put an arrow through his head.

The friendly banter he exchanges with Andrea isn’t so much light relief as a welcome change in tone, although there’s no sense of physical attraction between the two – unlike Glenn’s visibly uncomfortable but utterly understandable crush on Maggie Greene (Lauren Cohan). His hasty outburst of ‘The clap… uh, venereal disease’ and subsequent embarrassment is a wryly recognisable moment of adolescent awkwardness.

But no matter how watchable the secondary elements of the unfolding story are, the only plot strand which compares with Shane’s struggle to retrieve the medical equipment (which takes such a bashing on the journey from the school you wonder if it’ll ever function once it’s back at the farm) is the reason he’s gone looking for it in the first place: Carl Grimes’s struggle for life.

While Rick looks a bit zombieish through constant blood transfusions and Lori weeps out the contents of the Chattahoochee River, their son’s failing health reaches a critical level. ‘I think your boy is out of time,’ Hershel warns his parents. ‘You have to make a choice.’

They do; and although you’ll have to watch to find out the consequences of their decision, be warned there’s a moment not long afterwards that will have even the hardiest of viewers reaching for the tissues.

Then it’s back to the beginning and the reasons behind Shane’s Albie-ish decision to remove his hair. It’s clear that even in the fluid, ever-changing post-apocalyptic world, the fallout from what the former deputy has done will loom ominously over the episodes to come; and that – for the viewing public, at any rate – is a good thing.

Any worries that Frank Darabont’s departure from the show might lead to a reduction in quality have long since been put to bed. The Walking Dead remains as compelling as ever.

Airs at 9/8c on Sunday 30th October 2011 on AMC in the US.

Airs at 10pm on Friday 4th November 2011 on FX in the UK.

> Buy the Season 1 DVD on Amazon.

What do you think of Season 2 so far? Let us know below…