"Clara Who" is a criticism I've seen fired at Series 8 on many occasions - that Clara has taken up a disproportionate amount of screen time and development. Intentional or not, Flatline takes this complaint and plays it about as literally as one can get. The increased focus on Clara hasn't bothered me as such, but I don't appreciate the reduced focus on the new Doctor which it has necessitated. Surprisingly, in the one episode which is explicitly light on The Doctor, this is not a significant problem - leaving us with perhaps the most satisfying episode of the series so far.
When the TARDIS lands in Bristol and begins to shrink, Clara finds herself carrying The Doctor in her pocket and the Sonic Screwdriver in her hand. It's not long before she blurts out "Doctor Oswald" and it becomes clear to us why she has been given so much development: By developing Clara, it becomes easier to see the dark and mysterious new Doctor through her eyes, and it's finally all starting to pay off here. A bit too late if you ask me, but you probably didn't.
After 8 episodes of observing and sometimes judging, Clara essentially takes a field course in what it means to be The Doctor and it provides lots of ammunition for some commentary on his motivations and his methods. Among other things, we see The Doctor giving her guidance based perhaps on his own priorties:
"pretty soon a leader is going to emerge. You need to make sure that leader is you."
We also see Clara acting on her initiative, and we can practically taste the disdain in her voice when she coldly resolves that she needs to lie to her 'companions' to give them hope and keep them alive. Indeed, the turning point of the episode (and a neat contrast to Kill The Moon, where Clara is far less able to take charge on her own) can be summed up when Clara says "Doctor? What would you do now? No. What will I do now?" It's concerning to see her become more accustomed to the role later: casually ignoring her companion Rigsy's paintings and the manner in which she sarcastically manipulates him out of an unnecessary sacrifice.
Unsurprisingly this is Clara's strongest episode so far, but for the first time I feel like the character development displayed has been organic because all of the context and logic behind it has been clearly laid out.
The Doctor isn't sidelined in the story, despite being confined to the TARDIS the entire time. While we get a deeper glimpse into his personality not just through what Clara projects, but how he reacts to her ("You were an exceptional Doctor, Clara. Goodness had nothing to do with it."). But nonetheless, I still don't feel like he's been fully established in all the senses he ought to be. The ambiguity becomes more boring by the week.
The enemy of the story is perhaps the most unique and creative we've had in some time: 2D creatures from another universe. While the CGI is sometimes just a bit ropey, the creatures are wonderfully realised nonetheless - their early "dissections" of their victims being my personal highlight, but their concept was explored well on all fronts. However, I think they lost some of their edge when they transition to 3D. The animation is spot on - capturing a shambling, almost convulsive element - but it does bring the monsters into standard pursuing zombie army of doom territory. It's necessary to further demonstrate The Doctor and Clara's optimism, but the early insistence that they might not have ill-intentions was a bit repetitive and dull.
As if we haven't been spoiled enough, we get a clever resolution! Deploying the ever-enjoyable "Use your enemy's power against them" trope, Clara gets the creatures to restore dimensions to the TARDIS with some clever (if a bit improbable) use of spray paint. It's a small thing, but it's a refreshing change of pace for a series which has largely been lacking sharpness.
How The Doctor banishes the "boneless" from our universe is decidedly less impressive: Swaggering out of the newly restored TARDIS, he delivers a vaguely rousing speech (though nothing as defining as Eleven's, which means it falls a bit flat (lol)) and then uses the Sonic Screwdriver.
There is a line of justification earlier in the story. The Doctor states he has a hypothetical way of getting rid of them, but the TARDIS needs its full power back. But this is a singular mention, far ahead of the execution, so to speak. It is never made remotely clear what The Doctor... does. Not episode-breaking, but since the plan was said to be theoretical, to see it just go off without a problem is lacking regardless.
The plot generally is very much a by-the-numbers alien incursion. I do have to wonder what the creatures were actually up to. It's intentionally unexplained, but it's still disappointing that all they truly get to do is chase Clara and co. around. The supporting cast are very two dimensional (lol): existing primarily to either die or survive. It's not a terrible misstep, but it does keep Flatline from accessing my highest scoring tiers!
While I can call it satisfying, the key strength of Flatline is that it doesn't get an awful lot wrong. A fair few minor problems here and there, but none of them leave much of a mark. Certainly not enough to leave the character interactions and thematic strengths become smirched. But summatively, the aspects Flatline lacks prevents it from being cemented as among my favourites.