Holistic Review: One of the most original, frightening monsters to come out of new Who.

Jamie Mathieson is definitely a name to watch. Having successfully crafted a fresh story out of not one but two elements of popular fiction in Mummy on the Orient Express, this week Mathieson proves equally adept at creating a memorable menace that's entirely original.

Two-dimensional aliens are such an innovative high-concept idea, yet it's surprising that Doctor Who has never tried it before, because in retrospect, it feels like such a logical angle from which to approach creating a previously-unseen type of monster. And the Boneless (must we really stick with that name though? I think I preferred "the killer graffiti") are unquestionably one of the most alien monsters that have ever appeared in Doctor Who.

Starting from the premise that they're two-dimensional, their abilities are entirely in keeping with their unusual nature, and each additional power the Boneless develop feels like a logical outgrowth of what we know of them. Mathieson's best decision was to make them beings from a two-dimensional universe, which means they operate according to very different physical laws, and they can't be detected even by the TARDIS. Nor can they be detected by the naked eye; not only are they two-dimensional, they're either naturally transparent or they have the ability to camouflage themselves, so they're essentially invisible. 2D aliens are a novelty; invisible 2D aliens have a lot of potential, and as Mathieson develops the Boneless, their menace deepens. First, the Boneless can move along walls and floors, like invisible tapeworms. Second, the Boneless have the ability to translate (or "flatten") three-dimensional objects, including living organisms, into two dimensions. Third, the Boneless eventually learn to utilize three dimensions themselves, after an apparent trial run in which they successfully transfer George onto a wall like 3D sidewalk chalk art. Having gained this understanding of 3D, they acquire the ability to extrude themselves into a third dimension, by constructing crude body-analogues. Finally, their newfound facility with three dimensions allows them to un-flatten formerly three-dimensional objects into 3D again.

One of the things that Mathieson does really well in Flatline is to tease us with the possibility that the Boneless really aren't malevolent. In keeping with today's gentler, more tolerant outlook, many recent Doctor Who stories have included this twist that the monster isn't really evil, just misunderstood. In this season alone, that plot element crops up in Kill the Moon, Time Heist, Listen, briefly in Into the Dalek and Deep Breath (if we're talking about the dinosaur), and arguably even in Mummy on the Orient Express. It's a good lesson for the kids when the Doctor points out "that in a universe as immense and bizarre as this one, you cannot be too quick to judge." and it would've been fine if these horrible murders had turned out to be a misunderstanding by utterly-alien creatures, but the sad truth is that when monsters in Doctor Who are nice, it inevitably undercuts their fear factor.

In Flatline, each time a threat looks like it might turn out to be relatively innocent, Mathieson gives it a menacing twist that makes the Boneless even scarier. First, there's the possibility that the Boneless don't actually kill their victims, instead keeping them imprisoned but alive, like the people in the drawings in Fear Her. Second, even if the missing people are dead, maybe the Boneless don't realize that they're hurting anyone. Both these illusions are shattered in one of the story's most pivotal moments, when Clara and Rigsy find the recently-vanished PC Forrest's nervous system splayed over one mustard-colored wall. In that moment, we know beyond the shadow of a doubt that PC Forrest is no longer alive, and not only is she dead, she was deliberately dissected. That's no innocent attempt to communicate, that's premeditated torture, murder and dismemberment. Until that moment, the shot of PC Forrest screaming and clutching her leg as the Boneless drag it into the 2D plane was merely unnerving, but now Mathieson has invited us to view that scene while imagining how painful it feels. From that point on, our minds conjure up all kinds of horrible torture as the Boneless' victims are presumably flattened, examined and dissected while they're still alive, and suddenly disappearing into the wall doesn't seem even slightly safe any more.

Third, the people in the subway mural make us second-guess whether we were wrong about their fate. Like Stan, they seem perfectly whole, and when the images come to life and turn toward camera, we momentarily wonder if maybe the Boneless' early victims are still alive and simply trapped. Maybe the Boneless aren't quite as bad as we were starting to think? That's when Mathieson ratchets the tension up again: the images of the missing people are not the missing people. As the Doctor urgently tells Clara, "They're wearing the dead! Like camouflage!" And now we know that the Boneless are truly sadistic, essentially possessing and defiling the corpses of our dead friends and relatives in an attempt to pass unnoticed. The fourth and final straw comes when the Doctor theorizes that perhaps the Boneless are simply trying the only way they know to communicate, after first experimenting with 2D impressions like handprints and tire tracks... but establishing dialogue through mathematics only allows the Boneless to brag about their last victim, and taunt the humans about how powerless they are to prevent the Boneless' next murder. (As Fenton says, "They're gloating!") So as glad as I am that the Doctor tries to give the Boneless the benefit of the doubt, I'm even more glad that they turned out to be unrepentant killers. For once, that makes a nice change.

So, the Boneless have a unique and compelling background, intriguing abilities, and they're genuine monsters. What makes the Boneless terrifying is how they tap into several primal fears. The Boneless are not humanized in any way, and they are not sympathetic. You can't communicate with them, which means that, like psychopathic serial killers, they are unmoved by pleas for mercy or compassion. They murder people indiscriminately, so anyone might be next. They can kill with a touch, but that doesn't necessarily mean that your death is going to be quick; it may very well be agonizing, as your body is crushed as flat as a sheet of paper while the Boneless rip out your nervous system. And where are these torture-loving serial killers going to ambush you? Anywhere. Because they're invisible, and two-dimensional, they could be lurking anywhere on your walls or even on your floor. You can't avoid touching the floor, which means you could be killed at any time just by stepping in the wrong place. While they lack the visual impact of the Weeping Angels, the Boneless are just as difficult to escape, and in terms of how you're going to die if they catch you, the Boneless are even scarier.

The Weeping Angels are a good comparison in more ways than one, because the Boneless are the first monster in a long time that have serious potential for recurring. (They're arguably the first since The God Complex or The Waters of Mars, although to find an enemy of the Boneless' calibre, I think we have to go all the way back to the Vashta Nerada.) Flatline is actually about the monster, in contrast to many recent stories in which the monster plays second fiddle to the main villain (like the spider-bacteria) or isn't really the focus of the episode (like the Scovox blitzer). The Boneless aren't all destroyed at the end of the episode, merely banished back to their own dimension; and since we don't know how they infiltrated Bristol in the first place (or why they chose that particular location), we have no idea where or when or how they might try again.

In my opinion, the scenes inside the first victim's house are among the scariest in all of new Who. With hindsight, PC Forrest's death is unbelievably horrific and gruesome, and as the scene plays out, the Boneless' abilities are exploited to maximum effect. We're already twitchy after watching one character die, and learning that she was dissected, so when the door slams on Clara and Rigsy, it's obvious they're the next intended targets. Watching the Boneless flatten an innocent sofa is one thing, but realizing that they can also use their skills on door handles, trapping their victims with no means of escape, is truly frightening. It's also a brilliant way to turn the aliens' potential limitation into an absolute advantage. Likewise, when Clara and Rigsy come up with the clever idea of hiding in a hanging chair — the one way to avoid touching a surface that the Boneless can reach — this seems like a foolproof plan until we realize that just as the Boneless can flatten a door handle into 2D, so could they flatten the chain attached to the ceiling, followed of course by the chair containing Clara and Rigsy. There's nothing quite like a monster with a unique form of attack, and a script that knows how to show off that ability to its best advantage.

The Boneless are indeed very well scripted: their scheme is easy to understand, even if their planned endgame isn't revealed. I had relatively few questions about their plan, which is otherwise pretty watertight. What questions I did have aren't really plot holes, merely tantalizingly unexplained background details which could be explored if the Boneless ever do return.

• I can certainly understand why the TARDIS would become such an immediately attractive target for them, given that it's the only thing around for light years that possesses even more than three dimensions. But how did the Boneless manage to leach the TARDIS' dimensions? (Is it because they didn't originate in our universe that they can get around the TARDIS' usual safeguards?)
  
• What exactly do they do with all that dimensional energy? (Do they feed on it, or were they using it to power their own forays into dimensional expansion?)
  
• Assuming that they would have eventually flattened the TARDIS, would that have enabled them to learn to manipulate four dimensions? (Or, to quote Susan, five?)
  
• How do they attack the TARDIS remotely, as appears to be the case? With all of the murders, there has to be physical contact.
  
• As two-dimensional beings, how did they know the number on George's jacket before they absorbed him? (I guess they must be able to perceive some things in our 3D world? Or perhaps this is another early sign that they're adapting?)
  
• How are they able to tap into dimensions that must be even further beyond their comprehension than it is ours? After all, you don't see any human beings suddenly acquiring the ability to flit back and forth in time, like the Doctor's bluff in City of Death. (This does perhaps point to the Boneless not actually originating in a 2D universe; otherwise you'd think they would find the concept of 3D too alien to understand, much less to utilize. Unless they're just very talented researchers, or entering our universe has unleashed their mysterious previously-unknown dimensional-manipulation powers, like the effect of our yellow sun on Superman.)

Although two-dimensional aliens have never been seen before on Doctor Who, the basic idea isn't altogether unfamiliar. The Boneless feel rather like a Star Trek alien given a Lovecraftian background and X-Files motivations. If this were Star Trek, the Doctor's main goal would be to communicate with the aliens to reach an understanding (as in the TNG episode "The Loss"); if it were a Lovecraft story, the unknowable aliens from an incompatible universe would be hell-bent on conquering our planet, with little concern for the worthless human lives they brushed aside (that's actually not too different from Flatline); and The X-Files is where their deliberate penchant for gruesome deaths would come in. Although, in terms of their concept, the Boneless most reminded me of Threshold, a half-season US series about ongoing attempts, by aliens existing in more than three dimensions, to breach our universe and overwrite the DNA of life on Earth.

It always makes me happy when a story gives the companion a meaty plotline, and it doesn't get much meatier than forcing the companion to adopt the Doctor's role. With the Doctor stuck inside the TARDIS, it's Clara who has to investigate, win people's trust, and think on her feet to a greater degree than usual. It's no surprise that Clara excels at this (otherwise we wouldn't have much of an episode), but it's nevertheless extremely satisfying. Flatline provides massive growth for Clara, who realizes, when she takes control of the work crew over Fenton's objections, that she can absolutely hold her own as a leader. Her most Doctorish scene, hands down, is when she rescues a single-minded Rigsy from certain death aboard the train, using nothing but her wits, her oratory skills, and a hairband. Clara gets to show off her cleverness at numerous points during the episode. Aside from the examples I've already mentioned, she deduces that a shrink ray might be the link between the TARDIS' changing size and the missing people. (Amusingly, after scoffing at the Doctor's suggestion that she could possibly scare off Rigsy, this theory of hers has precisely that effect!) More importantly, Clara single-handedly comes up with a way to save the day, so that the Doctor can rescue the planet. Her idea to restore the TARDIS is so intelligent. Not only is she using the enemy's powers against them, by coaxing them into unleashing their dimension-restoring power (which is exactly what the TARDIS needs anyway) like a snake being milked for antivenin, she's also taking advantage of their tendency to view the world as 2D (how would they know that a 2D door wasn't a real door?) and, most importantly, utilizing the strengths of her team, by employing Rigsy's artistic skills to spray-paint a realistic-looking fake door. This is such a clever solution; I figured out where she'd placed the siege-locked TARDIS but had no clue that the door was a Rigsy original. This week's more central role for Clara perhaps explains why she was stuck in the baggage compartment last week, so in retrospect I find I can be more forgiving of one of the few elements of Mummy on the Orient Express that I wasn't entirely satisfied with.

Adopting the Doctor's persona not only gives Clara the chance to poke fun at the way the Doctor operates, it also puts her in the Doctor's shoes for once. On a character-development level, this is a really interesting opportunity to explore Clara's recent internal conflict. After her anger at the way the Doctor made her an accomplice in last week's episode, here she's willingly taking over his role, even down to lying to keep people alive. I was hoping that this experience might give Clara some more empathy for the Doctor, and help her realize how well he deals with the impossible situations that he finds himself in. And I think it does, although oddly the more prominent knock-on effect seems to be that the Doctor has lost some respect for her. Instead of congratulating her on a job well done, all the Doctor can bring himself to say is, "A lot of people died." (Oh, so now he's one to criticize?) I don't recall Clara ever resenting the Doctor for not being able to save everybody, so why is he doing it to her? Likewise, when he thought Clara couldn't hear him, the Doctor praised her with "I don't know if you'll ever hear this, Clara. I don't even know if you're still alive out there. But you were good! And you made a mighty fine Doctor." Yet later, when Clara asks him to reiterate that she was "good", he coldly retracts his praise: "You were an exceptional Doctor, Clara. Goodness had nothing to do with it." So he's changed his tune by the story's end; why? Was he really just delirious? It may have something to do with Clara's interpretation of the Doctor's methods. She tells the Doctor to his face, albeit in a matter-of-fact rather than judgmental way, that she thinks he would lie to people in order to save them, and that he thinks about the big picture more than individual lives. From what we know of the Doctor, there's some truth in that assessment, but we're given subtle hints on each occasion that the Doctor considers this appraisal to be inaccurate. After all, the Doctor wouldn't really lie to people outright for no reason, would he? Especially not the twelfth Doctor, who's more inclined to be brutally honest. And it's unfair to claim that the Doctor isn't concerned about individual lives. It's almost as if Clara remembers his behavior in Mummy on the Orient Express but not his explanations afterward, so I guess I can see why the Doctor's getting his feelings hurt. But that doesn't mean that Clara's entirely off-base, or that she didn't do the best job possible given the circumstances, so I'm rather miffed at the way he treats her. Some thanks that is for saving the world, not to mention the TARDIS, or his life! I really like that series eight is taking such care to explore the conflicts that the Doctor and Clara are working through as they come to terms with their new, less happy-go-lucky, relationship, and I'm eager to see how it continues to develop.

Happily, being stuck in the TARDIS doesn't mean that the Doctor is completely excluded from the action. He's still in touch with Clara via an earpiece and even sometimes directly through the TARDIS door, so he's constantly giving Clara suggestions. He's also the one who gives Clara the idea to escape through the window, figures out how to open up communications with the Boneless, and how to ultimately banish them, so along with supporting Clara, he's responsible for some of the crucial plot developments. His relationship with Clara continues to evolve, as he discovers that Clara was lying to him about having Danny's blessing to travel in the TARDIS. He doesn't seem to hold it against her; he just comments that lying is "a terrible habit".

Along with his creation of the Boneless and his contributions to the Doctor/Clara arc, I appreciate how thematically satisfying Mathieson's script is. Even beyond its exploration of the Boneless' nature, the common thread of 'dimensions' ties the script together. The Doctor, for example, is aghast that the TARDIS could be attacked in such a manner, in a line which also sheds light on the creatures' origin: "I'm from the race that built the TARDIS! Dimensions are kind of our thing!" Appropriately, graffiti is a key component of this story; as a 2D art form, it ties in really well to the theme of 2D aliens. Not only is it appropriate that one of the main guest characters is a graffiti artist, 2D art also proves to be the creatures' undoing.

Mathieson even includes some subtle commentary in his script. Both Rigsy and PC Forrest comment that the police haven't been doing as thorough a job investigating the disappearances as they might have, which in Rigsy's opinion is because nobody cares about the (presumably poor, lower-class) residents of the estate. The script also touches on the issue of urban art, and the question of whether it's a valid art form or merely vandalism. Rigsy's beautiful mural down in the train tunnels, where unfortunately it has no audience aside from maintenance workers and people fleeing for their lives from alien killers, is certainly strong evidence for the former opinion. The Doctor, too, validates Rigsy's talent, if not necessarily where he displays it: "Your last painting was so good it saved the world. I can't wait to see what you do next." I love that line, which hopefully encourages other street artists that their skills shouldn't be undervalued.

He also avoids potential plot holes well. For example, ordinarily I'd have a hard time buying that the TARDIS was about to be destroyed, but because the TARDIS dimensions are being leached, it's easier to believe that its shields and structural integrity might be vulnerable. He provides a neat explanation for why the Doctor doesn't just immediately dematerialize once he discovers that the TARDIS is in trouble: "The sensors are down, and I can't risk taking off with it in this state." There's even a good excuse given for why Clara's suddenly carrying a handbag large enough to accommodate the shrunken TARDIS. The only question that's entirely unclear, aside from how exactly the 2DIS works, is how the Doctor banished the Boneless back to their own dimension; but the story as a whole is so strong that this detail doesn't really matter.

Among this week's fun references, we have a reminder that the TARDIS has "acres of room" where Clara could keep her things in between adventures, the mention of a "shrink ray" which seems like a reference to Into the Dalek, my beloved door-opening sound returns (and this time it actually does open the door!), and the cloister bell returns. The script also fills in some previously-unexamined background details, which is always rewarding when done well. "Clara, it's always lighter," the Doctor tells her. "If the TARDIS were to land with its true weight, it would fracture the surface of the Earth." We've always kind of known that the materialized TARDIS only weighed as much as its exterior, but it's nice to hear it outright confirmed. A new feature is the TARDIS "siege mode", which turns it into a metal box resembling the TARDIS' default state, but without a door, so that nothing can get in or out. Ordinarily this mode can be disengaged from within the TARDIS, but the TARDIS' current lack of power means that the Doctor is now stuck inside until the life support runs out, which introduces yet another note of tension to the script.

Wow, Joivan Wade is a find, isn't he? I adored him as of the line "I just do graffiti. Not anything, you know, murdery or..." which he delivers with great facial expressions. I like that Rigsy is initially introduced as an undesirable vandal, before turning out to be a really sweet kid with amazing artistic talents. (Given that he's a street artist, surely his name was a nod to Banksy?) The Doctor initially writes him off as just another "pudding brain", but Rigsy demonstrates that he's an analytical thinker when (like the Doctor) his first thought is of a locked-room mystery, thus proving that Clara was right to keep him around. There's a subtle hint that maybe Rigsy doesn't feel that he has a future worth living for, when he puts up such a fierce resistance to Clara rescuing him from the train, but sadly it's not developed. His first instinct on returning to the surface is to call his mother, so he does at least have family who care for him. If only he'd joined the TARDIS crew (another guest actor that I want to make permanent!), we could've teased out his backstory eventually. After all, wouldn't a graffiti-artist companion be cool??? Also loved Wade's delivery of "Sorry, nothing, I was just thinking out loud.", his enthusiastic "So how'd you get this gig? Did you, like, study science or aliens or something?", his expression as Rigsy realizes that the subway mural isn't just a memorial of grief, the way his expression falls when a distracted Clara evaluates his work with "Yeah, not bad." (I mean, really. Did she even look at it?!), and his cute little shy goodbye wave.

Initially, Christopher Fairbank (Fenton) seems stern but perhaps not unreasonable, given that he's tasked with overseeing what are presumably a bunch of delinquents on a work detail. We're given a big hint about Fenton's personality when the Doctor mentions that it "takes quite a lack of imagination to beat psychic paper." and thereafter he proves to be little more than a pessimistic cantankerous jerk, who refuses to listen to Clara even when it becomes clear that she really is the only person keeping them alive. He doesn't even seem to have an ounce of regard for the innocent victims of the Boneless, dismissing them as "community payback scumbags" who are better off dead. (The Doctor's not much better, though, with his "maybe the wrong people survived"!) So it almost comes as a shock when he actually gives the Doctor and Clara a heartfelt "thank you" as he leaves!

The rest of the maintenance crew all seem to be community payback workers like Rigsy, yet he seems keen to distance himself from them as if they're undesirable elements, but they all seem quite nice. I mean, aside from Fenton, the one man who isn't one of them. Al (Matt Bardock) has a kind face, and Bardock is very good at expressing fear using mainly his eyes. George (Raj Bajaj) is the first to stick up for Clara when he thinks Stan's mocking her, and in general he seems like a sensitive guy. Astonishingly, the poor actor who plays Stan doesn't seem to have been credited, but I really liked his delivery of "Oh, sorry love, I didn't mean nothing by it."

James Quinn plays Bill, who I believe is the train conductor, and exemplifies how it only takes one great line to make a character relatable: "Is this official? 'Cause I've always wanted to ram something." I also loved his final scene, as he gives Clara a warm hug for having saved them, and then, to thank the Doctor for saving the entire planet, gives him... a weird disapproving look. Ha! It's nice to see that this Doctor does not inspire warm fuzzy feelings in the average human.

John Cummins (Roscoe) has just one brief scene in the teaser, but his shallow frightened breathing conveys Roscoe's terror as the Boneless close in. Jessica Hayles, too, only has a brief scene; she plays PC Forrest as somewhat inexperienced and out of her depth, which makes her sympathetic. And her screams of terror and pain are very convincing!

Turning back to the regulars, I want to spend some time praising Coleman and Capaldi's performance. This episode belongs to Jenna Coleman, who gives a great delivery of "But still, he's all right with us doing this, which I admit's a little bit weird, 'cause you'd think if he had a problem with me leaving stuff in the TARDIS, he'd object to me travelling in the TARDIS, but he's not, so...", "Ish? Don't give me an ish.", "Bristol! Doctor, we're in Bristol!", "Oh my god, that is so adorable. Are you in there?", "How are you gonna get out?", her acting as the Doctor shoves a sledgehammer into Clara's bag, her slightly apologetic "Apparently they're in the walls.", "Love you!", her very Doctorish "Fine, I'll tell you who I am. I am the one chance you've got of staying alive. That's who I am.", and Clara's increasing confidence on "Doctor? What would you do now? No. What will I do now?" As for Capaldi, I loved his delivery of "Neither is mine, until I get this figured out!", "I wouldn't like you to get squished accidentally.", "It's very very serious", and the very funny line "You really do throw your companions in at the deep end, don't you?" He also gives the Doctor a couple of moments that I can only describe as adorkable: his excitement over naming the "de-flattener" the 2DIS (oh gosh...) and his happy victory dance once he's scooched the TARDIS off the train tracks.

Douglas Mackinnon really impressed me with his direction this week. It isn't overly flashy, although he includes some eye-catching moments like the phone swinging on its cord in slo-mo after Roscoe is taken by the Boneless, and the slightly increased frame rate in many of the outdoor scenes. There were only a couple of moments where I felt it would've been helpful to hold the shot for a bit longer: first, the handprints and tire tracks on the wall of the estate, which didn't even register with me until my third viewing; and second, the freaky shot of George transposed onto the wall, which cuts away before the camera has panned out far enough for you to be entirely certain what you're looking at. Otherwise, I thought his direction was meticulous and atmospheric. Among my favorite shots were the opening, as we pan from a wall over to a close-up of Roscoe's scared face; our subsequent mounting horror as the camera (and effects, and music) reveals that the smear on the wall is actually the distorted image of Roscoe's face; the angle of the Doctor walking up to the TARDIS door and tilting his head to look at it; the Doctor and Clara simultaneously saying "What?!"; the pan from the TARDIS on the tracks up to the approaching train; the rapid zoom out as the Doctor pulls the siege lever; the shot of the sonic screwdriver's green light morphing into an actual traffic light for the train, which then switches to a red light; the shot of monsters rising from the tunnel floor amidst the steam; and the shot of the top of the Bristol poster peeling away from the wall. He does a really excellent job of framing shots in a way that leads the viewer's eye exactly where he wants you to look. The best example, for me, is the moment when Al gets taken by the Boneless. The camera is angled so that the tunnel roof fills more of the screen than usual, so I was expecting to see the Boneless rippling along the faintly-lit bricks. Thus, my gaze was fixed at a spot just above Al's head, which means that I completely missed the subtle background clue of the fingers extruding from the ceiling until — from my perspective, out of nowhere — the giant hand suddenly grabbed Al. I yelped, and covered my mouth in horror, as Al was yanked off his feet and dragged away. I'm not sure I've had that reaction to Doctor Who since Blink.

Needless to say, after that exciting moment of spine-tingling terror, I was putty in the episode's hands as the newly-three-dimensional Boneless started rising from the ground, like vampires or decaying zombies. I say "decaying" because that's the impression given by their shambling, jerky, unnatural gait and the sticky-looking strands of flesh stringing between their bodies and their moving limbs. They definitely move like creatures possessing bodies that they haven't yet got control of, in a manner reminiscent of stop-motion animation. The effect of their features shifting as they walk is also stunningly animated. So I have to give a lot of credit to the effects team for their work, because they succeed in realizing the Boneless in an appropriately chilling way. The 2D Boneless are eerie, too; as melted drawings, they actually look like rivulets of watercolor pursuing our heroes, and in the crazy-wallpapered room, their impressive camouflage ability makes it appear as if the walls and floors are rippling to life, or crawling with invisible ravenous worms. The effects also enhance the Boneless' menace as we watch them brutally flatten not just people, but inanimate objects like couches, as they gradually eliminate every possible refuge from their encroaching fatal touch.

Even aside from the Boneless, Flatline is an effects-heavy episode, and everything in it looks great. The effects that are relatively more simple, like the green beam from the 2DIS, the door handles un-flattening, the Boneless' energy discharging like electricity, and the Boneless being banished back to their own dimension, are just as impactful. I really loved the effect of the TARDIS starting to glow with blue light as the aliens' orange energy crackles around it, and the superb effect as the police box shell is restored and blasts the aliens back behind a forcefield. The miniaturized TARDIS is a fun idea, realized well both in its various prop forms as well as the ever-shrinking interior door. That half-size prop gives us possibly the best look at the TARDIS lamp that we've ever had! The shots of the Doctor matted onto the miniaturized prop look practically flawless, even when Clara picks up the model, although in a couple of shots, the Doctor's face looks noticably 2D as Clara shifts the TARDIS around in her hands. Their biggest triumph in this respect, though, is their integration of Peter Capaldi's hand with the prop. The shots of him waggling his hand out the door at Clara look amazing, as do the fun shots of his hand emerging from her handbag (ha! as the Doctor might say, that term has never been so accurate), but the most awesome is the memorable shot of the Doctor's hand emerging from the TARDIS to inch it off the railroad tracks, Addams Family style.

Sound effects are a major part of the episode too, because we can often hear the Boneless even before we see them. Whether they're moving inside the walls, emerging from the ground, or staggering along tunnels, they're accompanied by eerie noises reminiscent of hissing, buzzing, insectoid chittering, creaking leather, whistling wind, zombie-like breathing, or faraway screaming, all of which give the impression that something frightening is getting closer. Overall, Murray Gold's score is really good. He reuses some of the score from Into the Dalek as Clara meets Rigsy again, and there's one very jarring moment when the score suddenly turns comical after Roscoe has dropped the TARDIS down a shaft, but aside from those moments, the score is appropriately eerie. The tension of the teaser is amped up by Gold's thrumming score, and I also liked the delicately eerie Blink-esque music as Clara looks at the mysterious portraits, the evil windchimes when Clara and Rigsy venture into the room where PC Forrest disappeared, and the music as the Boneless recharge the TARDIS.

And I love the story's very X-Files title with its double meaning.

Minor points:

• Ach! They finally got it right last week, but now the title is disappearing along with the opening credits again. Rarrr.

• Couldn't the Doctor un-bolt the second exterior door to give him more room to get out?! He does open it later, after all, once the door's so small he can't get through it.

• As Fenton passes a paintbrush to Rigsy, Al tries to intervene: "Oh, come on, there's no need for this." No need for what? Making Rigsy paint over his graffitied name, which he has been brought out here expressly to do? Or does Al just think that Fenton's being unnecessarily sadistic about it?

• How did the Doctor move his chalkboard down to the main console room floor? I'm sure he must've had Clara's help, but it looks like a pain to manoeuvre down those stairs.

• Kudos to the location scouts, who have managed to find quite a picturesque pedestrian tunnel! I love the brickwork around the stairs.

• This week's Line I Just Don't Understand, as Clara squats to get a better look at the tributes left for missing residents:

  Stan: "Cheer up, love! Might never happen!"

  Eh? What might never happen? Clara disappearing? One of her friends disappearing? I mean, if Clara's looking at the memorial, you'd think he would assume she had already lost someone. (Rigsy does, after all: "I've lost someone too.")

• When Rigsy goes up to talk to Clara in the subway, he touches the portrait of his missing Aunt Karina. How come the Boneless don't take him then and there, like they do when Stan touches the wall later?

• Heh. Yeah, not really too many alternative possibilities for this one. (Oh, well, mad physicists, I suppose.)

  Clara: "Aliens?"
  Doctor: "Possibly. Oh, well, who am I kidding. Probably."

• I'm really digging the TARDIS' old-fashioned radio speaker!

• A laugh-out-loud line as Clara mocks the Doctor, although I was holding out hope for "intestinal parasites".

  Rigsy: "So, er, what are you a doctor of?"
  Clara: "Well, I'm usually quite vague about that. I think I just picked the title 'cause it makes me sound important."

• I was, at first, very confused by why Rigsy was just allowed to walk off the job site! Thank goodness for the later line about him returning late from lunch. However, this still doesn't quite explain how he's able to just walk into a crime scene! I suppose he thinks it's okay since Clara's a spy.

• Clara's facility with the sonic screwdriver is such that I have no choice but to assume that it can be controlled telepathically. We've never actually seen anyone adjust the settings, have we? and yet the sonic screwdriver can do whatever the user wants, with just the press of a button. I am, however, surprised that Clara would use the sonic screwdriver to sever the Doctor's only visual link with the outside, even if she is feeling vengeful!

• Ohhh, very nice!

  Rigsy: "It's bigger. On the inside."
  Doctor: "You know, I don't think that statement's ever been truer."

• PC Forrest is remarkably calm about Clara and Rigsy's appearance. I think I'd be a bit alarmed if someone claiming to be from MI5, but dressed casually, suddenly walked up next to me and stood there silently gripping a sledgehammer!

• Should I quibble over the fact that to a two-dimensional organism, even a flat rug would represent dimension #3? ...naaaaaah.

• I did wonder, for a moment, why the set dressers (or, equally, the owner of the home) had chosen to paint a sideways tree on the wall. Then I realized: That is not a tree.

• The desert mural on the wall of the first flat had me perplexed initially, but the truth finally dawned on me moments before the Doctor announced that it was a magnification of human skin. Chilling. (Not as chilling as a nervous system, but chilling!)

• "Got our bench!" says Danny, all chipper. And then, apparently, the internet explodes after a bunch of audience "slips of the ear" happen to coincide with BBC America's unfortunate subtitles. Whoopsie-daisy. (Thanks to Tumblr user picturesfromtheflood for the photo!)

• "Sounds, erm, kind of... active," says an impressively calm Danny, as Clara helps "a guy on community support" to "find his auntie" in a way that involves much grunting and moaning.

• After flinging herself through a window, Clara miraculously manages to avoid cutting herself on any shattered glass, even when she lets her bare hand flop out onto the glass-covered yard.

• I love lines like this, as Clara communicates with Rigsy while leaving a lot unsaid; but Rigsy clearly gets exactly what she means. Great performance by both actors.

  Clara: "They're very realistic. Who painted them?"
  Rigsy: "I don't know. A local artist, probably a grieving relative."
  Clara: "Did you ever meet them? Or did they just appear after people disappeared?"

• Nice delivery, especially by Jenna Coleman.

  Doctor: "It's true that people with hope tend to run faster, whereas people who think they're doomed —"
  Clara: "Dawdle. End up dead."

• I love this line! (Although it works better spoken than it does written!) And I love pie.

  Doctor: "Okay, let's start with pi. Even in a flat world, they would have circles. I don't mean edible pie, I mean circular pi. Which I realize would also mean edible pie, but... anyway."

• I'm not quite sure I understand what good it does to re-flatten the door handle. Is it because the new 3D creatures must henceforth interact in three dimensions? Why couldn't they simply revert to 2D and emerge on the other side of the door? They could probably have gotten through the gap in the door that way.

• I wonder why Fenton wanted to get the TARDIS out of Clara's bag? He doesn't seem to have been intending to throw it away, so what was he planning to do with it? (And why have they stopped to have this discussion, while the Boneless are still in hot pursuit?

• Flatline is just. so. imaginative! And not only imaginative, but well thought-through; after all, this is exactly the simplest solution to the problem. (Also, it's a good thing the Doctor has some familiarity with 1960s American sitcoms.)

  Clara: "No, you move the TARDIS, like... Addams Family."

• Coleman's best delivery of the episode! Oh, so good.

  Clara: "Okay, fine, yeah. And I'll always remember you."
  Rigsy: "Fine, you're great!" (or something like that)
  Clara: "Cause I was just gonna do this." (she attaches her hairband to the train controls) "No driver required. And I'd really like that hairband. But I suppose I'll just take it, will I, and every time I look at it, I'll always remember the hero who died to save it."

• When Clara told Rigsy she had a commission for him, at first I thought she was going to ask him to draw the TARDIS! I wasn't quite sure how a Boneless-reconstituted duplicate was supposed to restore the original though. (And as it turns out, they wouldn't have been able to 3D-ify a hand-drawn TARDIS anyway!)

• It's a good thing the Boneless are such slow walkers! Otherwise, aside from having caught up to Clara's gang on more than one occasion, they might've reached Clara's showdown point before Rigsy had time to finish his masterpiece, or before they'd managed to paste it up!

• One slightly confusing shot: as the Boneless are zapping away at the fake doorway, and the camera pans around to the other side of the wall, does it go through an archway or through the wall itself? It looks more like the former, but I'm hoping for the latter, because otherwise why would the Boneless bother trying to un-flatten the door handle if they could walk through an immediately-adjacent gap in the wall? (Oh, there's absolutely an archway there; that's what the TARDIS flies through in order to reach them! Silly Boneless. I guess as 2D beings, they never thought to keep looking further down the hallway!)

• Ooh, I just noticed that entire panels of the TARDIS console swing outward, to enable interior repairs! That's rather nifty.

• Clara gets the triumphant "that's who I am" moment, but the Doctor trumps her with this brutal monologue. At first I thought he was talking to Clara, and then, wow.

  Doctor: "I tried to talk, I want you to remember that. I tried to reach out. I tried to understand you. But I think that you understand us perfectly. I think that you just don't care. And I don't know whether you're here to invade, infiltrate or just replace us. I don't suppose it really matters now."

• Blunt Doctor returns:

  Doctor: "I'm sending you back to your own dimension. Who knows, some of you may even survive the trip."

• Let's hope the Doctor was able to banish all of the Boneless back to their own dimension, eh? We saw so many wriggling invisible wall-worms that I would've sworn there'd be more than six of them!

• Another surprise appearance by Missy! I like that she's being doled out in small scenes here and there. I find it keeps me intrigued because we don't know when to expect her, and she certainly never overstays her welcome, so we're eager to see more. It's a great way to build interest for the finale. But I'm getting ahead of myself. This time she has a plot twist to spring on us: "I have chosen well," she cooes, re Clara. Oooooh, more fuel for the "woman in the shop" fire then.

• I have to admit, next week's promo doesn't look the tiniest bit scary, nor does it look like there's much night in the Forest of the Night, so I'm not sure how excited I am about it. I'm afraid the episode may not live up to its evocative title. But I didn't think the trailer for Flatline looked all that exciting either, so yet again I'll reserve judgment. It has occurred to me that the producers are doing a really good job this season of creating promos that are as spoiler-free as possible, like the way Clara was completely absent from the Mummy on the Orient Express trailer, or how the Caretaker trailer was basically the teaser plus one shot of the Scovox blitzer. I really appreciate that effort to keep us unspoiled, and if it results in some episodes looking rather less interesting in the promo, I can absolutely live with that.

As an episode of Doctor Who, it's pretty near perfect, and as a scary episode of Doctor Who, it puts most of the other revived-series contenders for that title to shame. For once, the hype ("an extraordinary episode", according to Peter Capaldi in a video interview on October 16) was not wrong. Can we go ahead and sign Mathieson up for series nine now, please? In fact, I'm about ready to bring him onboard as showrunner once Steven Moffat retires from the position. Either way, like Rigsy, I can't wait to see what he brings us next.