Holistic Review: An inspired parallel-universe subplot provides a magnificently bleak resolution, giving us a story that's simultaneously fun, tense, compelling, and pretty unique in Doctor Who history.

You really have to ask yourself: why didn't Doctor Who do parallel universes more often? Why never before this, and why never again until Rise of the Cybermen? The advantage of it being such a rarity is that the magic of Inferno is perhaps more special, because parallel universes just don't fall under the usual remit of the series, so this particular story has more impact than it would on, say, Sliders. The sad thing, though, is that clearly this series can do parallel universes very well, and Inferno is surely one of the most powerful entries in the whole series canon. It's interesting to consider what this story would have been without the parallel-universe element: just another four-part runaround in a scientific base, with the Doctor trying to stop a madman's scheme and avert global catastrophe. But, by giving us a glimpse into another universe, we can see what happens when the Doctor doesn't win in the end. Aside from this being an exciting story in its own right, it hugely raises the stakes for what's happening in our own universe, because we know the consequences if the Doctor doesn't stop our Stahlman.

I must praise writer Don Houghton to the high heavens, because he has structured this plot so deftly, that in my opinion it's one of the few stories that really justifies its longer-than-usual length. There probably is padding galore in here (after all, the Doctor does keep getting locked up) but he makes it all so incredibly entertaining, and from episode 3 onwards, the whole thing is also so incredibly tense! He's organized the story very cleverly; episodes 1 and 2 give us the background to the Inferno project (the Primords and some unspecified danger caused by the drilling), episodes 3 and 4 set up the threat of the parallel universe (a totalitarian regime with harsh punishments for even minor offenses), episodes 5 and 6 rake us over the coals with the life-or-death struggle in the parallel universe (hordes of Primords, certain doomsday-by-lava and an oppressive feeling of inevitable doom), and by episode 7, we know that the Doctor has got to stop the drilling in our universe at any cost. Of the lot, episode 6 is unquestionably the best: the Primords are on the loose, the heat is rising, the drill core is threatening to explode at any moment, and our gang must struggle to repair the Doctor's power supply... all so that he can escape, leaving the others to their fate. By this point we've come to care for the alternate Shaw, Sutton and Petra (if not the Brigade Leader) because of their astonishing selflessness in helping the Doctor to escape their fate, to save a world they never knew existed until a few hours before. We fully believe the Doctor's heart-rending wish that he could take them all with him, and we want to see him save their lives. But he can't... and the almost unbelievably bleak cliffhanger to episode 6, which surely must rank as one of Doctor Who's finest, has tremendous impact when we realize that, moments after we cut away, all three of them were engulfed in a flood of boiling lava and horribly killed.

Given how fascinating the alternate universe is, it's impressive that the digressions back to our universe manage to work so well. Because the timeline in the parallel universe is slightly ahead of ours, these trips could have felt like redundant flashbacks because they're just mirroring what's already happened in the parallel universe. But they work because we have some idea how events might turn out - for example, when Sir Keith leaves for London, will Stahlman have him killed, or will there be a different outcome in our universe?

This story is also given no end of help by the talented cast, who make every single character notable. Olaf Pooley is marvellously wicked as Stahlman, whose ego is very inflated by the power he is allowed to wield, and who is clearly one of those scientists who is determined to carry out their research with absolutely no regard for the consequences. The horrifying thing is that no matter how many regulations he bends or ignores for the sake of results, nobody can lift a finger to stop him, possibly because the government agrees with Stahlman about the value of his research. So his greed for knowledge and success runs unchecked, and he nearly destroys the world as a result. He apparently has amazing willpower, as he manages to resist the influence of the green ooze for far longer than anyone else (the Doctor intimates that this is because he only got a tiny bit of it on his skin, but it still seems to spread very quickly, so I think some mental resistance was involved too). I find the scene in which he defiantly grabs the heat-shielded container with his bare hands to be very interesting; he's seen people handling the intact container with gloves already, he knows how hot it is, and he knows that the glass is cracked. To seize it with such astounding carelessness, and then nonchalantly brush off questions about its intense heat, seems to indicate that he's foolhardy, sees himself as being practically untouchable, and is determined to always be right. I mean, my goodness, when the Doctor points out an error that would have cost him thousands of pounds, is he grateful? No, he sulks and grits his teeth and mutters "I'm rapidly losing patience with that man." He must have been infuriating to work with, and I don't know how Petra put up with him.

Sheila Dunn actually threatens to be the serial's weak link in casting, because she often delivers her lines in a flat monotone (witness her sounding nothing so much as bored on the line "We're just going to die in here. I can't take it in."), but I think part of this is due to Petra's ice-queen façade. It's pretty clear that Petra's adopted this persona as a means of dealing with the constant chauvinism at work, and as a way to assert her position of authority and emphasize her brains over her beauty. I mean, even Liz, in the boys'-club world of academia, has developed a steely spine and a talent for no-nonsense talk and withering glares. What's nice is that over the course of the story, we do see Petra start to come out of her shell and display some emotion, either as a result of unimaginable stress or during the process of turning from Stahlman's lapdog aide into an independent thinker who does what's right rather than what Stahlman says. I still don't think that Dunn is the strongest actress, but she portrays Petra's arc well and makes her both likeable and strong, which is impressive.

There's also a rather sweet, if improbable, love story on display here. Poor Greg Sutton blunders wildly down the wrong alley with Petra, first when her "How do you do?" is met with the sleazy "All the better for seeing you, Petra." And they've just met! Familiar much? Not to mention "sexual harrassment" - it's no wonder Sutton was "snubbed". (Pleasingly, on the parallel world, Petra's actually the assistant director rather than Stahlman's assistant, and she calls Sutton out on his overfamiliarity. Excellent.) Then he follows this up with the patronizing "I'm not nervous, darling, I'm terrified." But once he starts to respect her as an equal, valuing her opinion and expertise, and persuading her to see his side of the situation, and once she sees that he genuinely knows what he's doing and is an asset to the team, she seems to come to realize that he's a good man who can be trusted, and she starts to like him and open up to him more. They get a great scene in the parallel universe, when Sutton forces Petra to realize that they've been abandoned, and finally Petra cracks and shows some emotion. It's a surprisingly believable little love story with very unlikely beginnings. And I like the notion that no matter what the universe, the two of them are destined to end up together. In fact, it's possible that because Sutton managed to win Petra over earlier in our dimension, that contributed to its salvation, because he's able to convince her to go against Stahlman's orders and halt the drilling.

Derek Newark is likeable as the earnest Sutton, who knows what needs to be done but can't seem to convince anybody else to believe him. He's one of the few people who will actually stand up to Stahlman, earning him the professor's wrath, of course. As an ally for the Doctor, it's nice to see that he's just as loyal in both universes, being quick to believe the Doctor's stories and just as quick to support him, possibly because he senses that the Doctor is a kindred spirit with the same goals in mind. Along the same lines, Christopher Benjamin's Sir Keith is an equally staunch ally, who actually has some power to do something about the situation. Stahlman's determination to stop him - more or less murderously, depending on the dimension - is rather chilling. And Sir Keith isn't even some opinionated government flunky who just wants things to go his way, he's a likeable man who has a strong sense of ethics and, like Sutton, wants to be sure that the project adheres to safety regulations. Anybody who would attack a man like that is in serious need of help.

Then we have our regulars. Nicholas Courtney is just amazing in this story. The Brigade Leader is recognizably our Brigadier, but so, so different. Both have commanding personalities, and both make clever deductions about their situations. But where our Brigadier is friendly and amiable, the Brigade Leader is icy and calculating. He's also cruel and borderline sadistic, seeming to relish his power as much as Stahlman relishes his. He's also shrewd enough to realize that "John Smith" is an "obviously false" pseudonym. The physical difference alone is remarkable, with the Brigade Leader's eyepatch (oh, that eyepatch...), scar and lack of reassuringly familiar moustache. (Nice that Courtney got to play a few scenes without prosthetic facial hair this season!) When the world literally starts to dissolve around him, all the Brigade Leader has left is his procedure, and he clings to it like a drowning man to a life-raft. His refusal to let the staff leave their posts, even in the face of certain death, is rather shocking. And then we discover that he's desperate to save his own skin at any cost, selfishly plotting ways to escape his fiery death, even if it means killing the Doctor (and you can't really blame him; the Doctor's reasons for not being able to rescue him must seem terribly flimsy to a man who's about to be simultaneously burned and boiled to death).

John Levene gets an even more startling cross-dimensional change, as our dear sweet Benton, who ordinarily wouldn't hurt a fly unless it was an enemy fly wielding an AK-47 and he was under orders, turns into nothing more than a brutal thug who hauls people around and seems to have a thirst for blood. He snarls orders more effectively than I would have guessed - witness his "On your feet!" and "Your trouble is, you talk too much!" His scream when a Primord touches him is absolutely bloodcurdling. I am a little surprised, though, that trained soldier Benton so easily falls for the Doctor's little "Come over here. Look at this magic trick!" business. Why does he even come when the Doctor waves him over?

Normal!Liz doesn't get a whole lot to do in this story, aside from fetching things for the Doctor, wandering around looking for him while he's gone, and tending to him once he returns, but Caroline John really gets to let her hair down (in an entirely metaphorical way) as Section Leader Elizabeth Shaw. It's a great performance, mainly because Shaw starts out very antagonistic toward the Doctor, showing absolutely no remorse whatsoever at her treatment of him or his ultimate fate. She almost seems disgusted with him for daring not to obey their orders. I love the "heart-to-heart" between the Doctor and Shaw in the cells, when she's clearly trying to be reasonable but is still way overreacting by our standards. But by the end, she too has come to realize that the Doctor was telling them the truth all along, and that he's much more worthy of her loyalty than her self-serving Brigade Leader, who she ends up murdering to save the Doctor's life (although, as Sutton said, being shot was probably a blessing. One wonders if, after the cliffhanger, she didn't pass her gun around to the whole group.).

As for Pertwee, he turns in a fantastic performance that may be one of my favorites of his, ever. I think the reason he works so well in this story is that when he needs to be frantic and angrily persuasive, he does it with aplomb, but when he's stranded in a hostile, depressing parallel universe, instead of responding with bluster and anger, he responds with lighthearted quips that help to elevate the mood, and he's disarmingly friendly in the face of hostile forces. I think it's largely because of Pertwee (and Houghton's scripting of his lines) that the parallel-universe scenes qualify as "fun"... even though the Doctor is fighting for his very life (not to mention the lives of everyone else), he tries to make light of the situation, which means we don't have to take it too seriously either, and we can enjoy all the little differences between universes rather than being horrified by how terrible it all is. It's also nice that he obviously has great respect for Liz, in both universes, which just makes me wish that she'd had a longer tenure as his companion. One also has to ask, too: how is he so certain that he doesn't exist in this parallel universe? Isn't it just possible that he's got a duplicate running around somewhere too?

Even though they probably fall under the heading of "random monster added at the last minute because you can't have a Doctor Who story without one", I really like the Primords. They could have ended up looking ridiculously ape-like, or just plain feral, but actually they evoke werewolves more than anything. They still seem to be intelligent, although not very intelligent; the transformed Wyatt wants to use his gun as a club, not realizing that it would be more effective if he fired it. The Primords are fierce predators, and if they don't beat you to death, one single touch on your skin will turn you into one of them in a most painful way, which appears to involve some of that green goo that burns your skin and won't wipe off. I love green goo. It's also very cool that the Primords possess some of the qualities of that green goo, like having a very high body temperature which not only causes them to thrive in (and, indeed, require) hot surroundings, but also transfers itself to anything they touch, giving them the ability to turn metal objects red-hot and scorch anything flammable. The wrench that the Brigadier finds at the first crime scene is an extremely intriguing touch, as is the scorch mark on the wall behind a dead Primord. And the Primords' blue skin is an interesting choice; it's a cool color rather than a warm one, and it's not the same color as the ooze that transforms them, but it works quite well at looking freaky and unnatural. One wonders if the Primords would have been uniquely suited to survive on an Earth swathed in lava and hot gases. And they make a very frightening snarling sound. I also find myself wondering if the Primords are being controlled by some kind of intelligence that inhabits the ooze. Stahlman sometimes acts as if he's being controlled by an outside influence that's forcing him to achieve penetration zero as quickly as possible, to accomplish some devilish purpose. Could there be some malignant force behind the ooze and the Primords that will be able to escape if the Earth explodes?

I love, love, love the direction by Douglas Camfield and Barry Letts. Lots of great angles here, and clever cuts. There's an inspired one toward the very beginning, as Slocum attacks a worker, and as he raises his arm to strike, we cut to Benton hammering a nail into the wall. Brilliant! All of the chase scenes over the silos are amazingly shot, too, between the scenes of various characters sidling along the railing by a steep drop, to the shots from below of characters crossing walkways or confronting Primords with fire extinguishers, to that amazing stuntfall. There's also a nice subtle shot of Stahlman's hand, just after he's started to change, when he's checking his watch and you can see his blue palms if you're looking for it. We get a very amusing shot of the Doctor rising up into frame with a trash-can lid balanced on his head (just like out of the cartoons!) as he's hiding from the soldiers; the interrogation scene is very well-filmed, with lots of quick cuts that reinforce how quickly the Doctor is being pounded with repetitive questions; a nice shot of the Primords advancing out of the steam-filled bore room; some great editing in the scene where Benton is horribly attacked and subsequently turns feral; and a well-timed shot of the Brigade Leader, Shaw and Petra toppling over as the tremors hit. One of the freakiest scenes must surely be the one in which Stahlman locks himself inside the bore room so that he can infect all of the unconscious and defenseless technicians, one by one; and likewise the shot in which Stahlman almost reluctantly smears the horrific ooze on his own face. I also like the camera following Section Leader Shaw from behind, although I think her reveal is a bit mishandled - it would've been more shocking to hear the Doctor's "Liz?" from off-camera and then see her turn around in close-up. Da da dum! But, alas, we get a big pause before she turns around, and when she does, it's a medium-shot, so we don't really see her face that clearly. Tsk. The Brigade Leader, on the other hand, gets an excellent reveal. There's one other bizarre shot in part 7 that's attempting to be a close-up of Stahlman's eyes, until Pooley starts swinging his head around and wildly out of the frame.

And yay for the stuntpeople! Aside from that amazing fall from the top of the silo - and, for that matter, all the work atop the silos, which must have been really challenging - we also have a very nice fight scene in Bessie as the Doctor tries to elude the fascist guards. There is a rather amusing scene in the bore room, in which the Doctor and Stahlman are fighting, and Stahlman flips the Doctor over his shoulder... then kindly helps him up, just so that he can flip him over his shoulder again!

There actually aren't a whole lot of effects in this story, or if they are, they're done so well they're unnoticeable. But I do really like the whirling effect that signals a narrative transition between universes (the sound is especially cool), and whatever filter(s) they use to indicate the rising heat outside really works wonders for the atmosphere.

Minor points:

• The title credits superimposed over flowing lava are cool; I love these experimental titles. They may be a bit jarring, but they're fun, and this one really establishes a nice atmosphere.

• Yet again we have a silly man who just can't resist the urge to reach out and touch an unknown and potentially toxic substance with his bare hands. I'm trying to tell myself that it's an understandable thing to do, since maybe Slocum assumes that it's just motor oil or something. Then again, the fact that he seems compelled to touch it might lend weight to my "it's intelligent" theory.

• We spend an awfully long time scanning the photo of Lethbridge Stewart's school days (although not as long as the Doctor does!)... is Nicholas Courtney really in that photo? If he is, we certainly don't get to see him. And if he's not, then what was the point of that scene?

• From the "Take me to your leader, Earthling" file:

  Sir Keith: (to Sutton, re: the Doctor) "Come, I'll introduce you."

• Giggle. The readout in the Doctor's lab measures things in MEGGA-volts.

• When Slocum attacks Bromley in the reactor control room, he's on the phone with someone. Doesn't that person wonder where he went? And possibly why he's screaming so? Unless that's always how he says goodbye. "I love you too, honey. Don't wait up for me. Okay then. AAAAAAAAAIGHHHHHHHHAAAAAAAHHHHHHHHHHHHhhhhhhhhhhhhhhhhhhhh.... *click*"

• Oh, that Stahlman, you can read him like a book. When the Doctor says he knows what the problem is, Stahlman snipes at him, clearly feeling that his position is being threatened, but once the Doctor says that he was wrong, Stahlman obviously perks up!

• Love this line:

  Sutton: "All right, so it was some kind of accident. They happen, you know! You have to make allowances, take precautions!"
  Stahlman: "I can make no allowances for incompetence, Mr Sutton."

• From the "oo-er!" file:

  Sutton: (to Petra) "Well, if you really want to show your gratitude, there are one or two things..."

• This project is clearly über-concerned about fire safety. Not only do they mount fire extinguishers on just about every available inch of wall space, they also dangle them off random metal railings along walkways and at the top of silos. Because you know those metal walkways are major fire hazards. Flammable as all get-out.

• Sooooooo... in another of those "it reminds me of something... but we'll never know what" moments... what exactly is this supposed link between Slocum and the Krakatoa explosion? They both involve heat and underground liquids? If my "intelligent ooze" theory is correct, is the Doctor saying that that thing made Krakatoa explode too? Or did it erupt because the Javanese were trying to drill through it to reach the center of the earth? Silly Javanese. (Everyone knows you're not supposed to start drilling to the center of the earth through a mountain. Pff!)

• I loooooooove the container that they put the green goo in. I want one too! What would I do with it though? Maybe I could put my mustard in it. And I could tell people "Be careful, don't touch the mustard or you'll turn into a slavering throwback creature and try to live in my oven."

• Mwahahaha! It must be said that no Doctor is better than Pertwee at deflating pompous idiots:

  Doctor: "Yes, well, I'll tell you something that should be of vital interest to you, Professor."
  Stahlman: (dubious) "That what?"
  Doctor: "That you, sir, are a nitwit!"

• And then the Doctor totally manipulates and patronizes Liz... and she just lets him do it, with a sweet smile and everything!

  Doctor: "Liz, go and check the tri-gamma circuits on the console again, would you?"
  Liz: "Why do you want me to do that?"
  Doctor: "Look, please, don't ask any questions, there's a good girl."
  Liz: (smiles) "All right."

• Ha! Sneaky Doctor, going over to switch the power to his lab back on after Stahlman has just disconnected it. (Meanwhile, Stahlman is engaged in some subterfuge of his own, as he removes a microcircuit from the computer...)

• Errr, where does Liz get that door opener from? When she left the Doctor's lab, she had to have him open the door for her. (Was she just being lazy? "Doctor? Please open the door for me, I can't be bothered to open my handbag right now.")

• You know - why exactly is UNIT here? It doesn't seem to be anything directly related to the Inferno project, although the Doctor is certainly trying to offer help in an advisory capacity. (Is that why they're letting him siphon off some of their power? As a way of saying "thanks for the hand"?) Were they just brought in to investigate the unsolved murders?

• You know, when trying to remain inconspicuous, heading for higher ground (and clambering up staircases and along walkways) is not generally recommended, as far as I'm aware. So why does the Doctor always, always seem to head straight for those silos whenever he's trying to avoid being seen? Does he assume that soldiers only ever look straight ahead or down?

• Meanwhile, for all his knowledge and experience, the Doctor is remarkably slow on the uptake when he gets sent off to a parallel Earth. You'd think a completely renovated lab would be a hint, and squads of soldiers firing at you would pretty much seal the deal. But when he sees Liz sporting dark hair and a black uniform, does he ever stop to think that she might not be his Liz? No, he assumes she's heading off to a swinging party in S&M gear. Tsk.

• Nice delivery by Pertwee, taking the mickey out of the Brigade Leader:

  Doctor: "Yes, I should very much like to see him."
  Brigade Leader: "Would you indeed?"
  Doctor: "Indeed, I would!"

• Of course, the Brigade Leader promptly gets his own back, in this chiller of a line:

  Doctor: "But I don't exist in your world!"
  Brigade Leader: "Then you won't feel the bullets when we shoot you."

• And the verbal sparring continues:

  Brigade Leader: "You are giving us a great deal of trouble!"
  Doctor: "I'm delighted to hear that."

• Now, back in our world, they'd discovered the leaking green ooze right at the start of the story. But in the parallel world, it appears that they're only just now discovering it, despite the fact that their drilling project is more advanced. So how is it that Stahlman and everyone else has already gotten turned into Primords? Maybe in both universes, the leak was actually there for a long time (and infecting people) before it built up to a level that the systems noticed?

• He means "translate", surely?

  Sutton: "Can you transcribe what the computer's saying?"

• Nice delivery by Pertwee, and nice acting by both Pertwee and John:

  Doctor: (to Section Leader Shaw) "Did you ever think of becoming a scientist? Yes... yes, I can see that you did."

• So the Primord in the next cell comes at the Doctor, raaaaar!, and bends the steel bars like they're made of putty, so the Doctor... runs out of the cell and shuts the door behind him, naturally. Which of course stymies the Primord, who does not realize that exterior bars are just as easy to bend as interior bars. So, it just hangs around inside the cell, looking fierce (and not in a Tyra Banks way).

• The Doctor gets some really classic lines in this story:

  Doctor: "If you break through the Earth's crust now, you'll release forces you never dreamed could exist. Listen to that! That's the sound of this planet screaming out its rage!"

• Okay, fickle totalitarian régime. One minute you're all set to shoot the Doctor as a spy, and the next you're letting him go gallivanting off into the bore room with Sutton to give his professional opinion. I suppose desperate times call for desperate measures, and strange bedfellows, and all that.

• Nice analogy:

  Doctor: "Compared to the forces that you people have unleashed, an atomic blast would be like a summer breeze."

• It must be said at this point, the Doctor's acting all high-and-mighty about the Inferno project tampering with forces beyond its ken... but if he knew what a powerful and catastrophic destructive force was going to be unleashed, why did he ever go along with the idea and help the project to begin with? He's like that guy who always says "I told you so" when things go wrong, despite never having said any such thing.

• Me wonder: is C0₂ really that cold, that it would hurt something with a high body temperature? I didn't think it was chilled, just under pressure. Wikipedia tells me that if you touch the nozzle of a CO₂ fire extinguisher while discharging it, "your hand may freeze to the extinguisher", but that's the only implication that there's any chill involved. Andrew, my source for all things chemistry-related, tells me that gas cools as it expands, so the CO₂ only feels cold as a result of having been pressurized, despite the fact that inside the extinguisher it's at room temperature. Look what I have learned! Thank you, Doctor Who! (and Andrew!) (and not Wikipedia, nyaah.)

• The Brigade Leader is not shy about making his true feelings known:

  Shaw: "The Doctor has some sort of device that could get him out of here."
  Brigade Leader: (pointedly) "Only the Doctor, of course, not the rest of us."

• The scene with Sir Keith and his driver is great - we learn that the Stahlman of our universe is, at least, not as bloodthirsty as the parallel-universe Stahlman, but we get a nice little twist ending as well, when Sir Keith ends up injured even without a hired hit-man.

• I was getting a little irritated noticing all these fire extinguishers (well, at least three) ringing the control-room wall, and none of the characters even thinking of picking them up to defend themselves. Happily, the Doctor does grab two of them on his way out, so that made me feel much better.

• Hee, poor Benton:

  Benton: "Wall, that's just it, sir. Professor Stahlman won't come. He says he's too busy to..."
  Brigadier: "Too busy to what, Sergeant?"
  Benton: "He says he's too busy to waste time bandying words with a pompous military idiot, sir."

• Woohoo! You tell 'im, Petra!

  Brigade Leader: "How long is all this going to take?"
  Petra: "I don't know."
  Brigade Leader: "Well, can't you hurry it up, Dr Williams?"
  Petra: "No, not if I'm to do the job properly."
  Brigade Leader: "You must! We've very little time!"
  Petra: (verge of tears) "Brigade Leader, I'm trying very hard to carry out a complex scientific task under impossible conditions! You will not help matters by bullying me."
  Brigade Leader: "You are insolent, Dr Williams."
  Petra: (fed up!) "Am I! Then it's about time that you learnt that some problems just can't be solved by brute force and terror!"

• You know, if the Time Lords used to dimension-hop all the time back in these days, then I wonder why it was so hard for the Doctor to get back? Is it only a power issue? Or might it be because his memory of how to operate the TARDIS has been wiped? If so, that would make a rather neat package, and it would mean that this is the one era of the entire show in which they could have pulled off this kind of storyline.

• Section Leader Shaw demonstrates that her respect in her leader is really slipping (assuming that it was ever there to begin with), and a nice performance by Caroline John. It's a wonder he doesn't slap her:

  Brigade Leader: "I'm thinking about the safety of all of us."
  Shaw: "Oh yes, yes, of course you are."

• Interestingly, although Shaw doesn't seem to be the Brigade Leader's biggest supporter right now, you still can't be 100% sure that she doesn't support his idea. There's always a chance that deep down, she wants to abscond with the Doctor's TARDIS console too.

• As soon as Petra cries "It's no use! I'll have to go through the whole wiring system all over again!", your heart just sinks. It's clear that this little group doesn't have much time at all, and the odds seem very much stacked against them at this point. Great scene. And your heart sinks again watching the group race back to the Doctor's lab... but realizing that they haven't succeeded in doing anything, and even if they reach the lab, they're all going to die. (Of course, most of them die anyway, but that's kind of beside the point.)

• Great delivery by Nicholas Courtney:

  Doctor: "Hysteria won't help us, Brigade Leader."
  Brigade Leader: "Nothing will help us! That bore's going to blast any minute, and we'll all be roasted alive."

• The fight between Sutton and the Brigade Leader is great, the Brigade Leader finally having realized that everyone else is handling the situation better than he is, and lashing out in anger and cowardice. It's clear that he's scared and desperate and not a nice man to know.

• First thought: woohoo, yay Petra for going back and trying to fix the wiring! Second thought: ...and now you're alone in the room with a sleeping Primord...

• Bwa! Someone must put this on a bumper sticker:

  Stahlman: "Safety margins are for cautious old women."

• Errr... is she slightly delusional? I don't remember her being a licensed physician, although the Brigadier does say in Spearhead from Space that she has (some kind of) degree in medicine.

  Brigadier: "I'll send for a doctor."
  Liz: "I happen to be a doctor, Brigadier, remember?"

• Love watching Sutton and Liz foment rebellion in Petra. Another woohoo! Her new steely backbone, when she confronts and stands up to Stahlman, is awesome.

• One can only imagine what the Brigadier makes of this line:

  Doctor: "You know, you really do look better with that moustache."

• Interesting. In the entire story, nobody ever actually says that the entire alternative Earth was destroyed, do they? Maybe the bore-hole did end up just being a massive volcanic eruption. (although, of course, who knows what effect an eruption like that would have on the Earth's climate...) In any event, it's quite possible that only the UK and perhaps part of Europe were actually wiped out, but the rest of the world managed to survive. I always figured that the bore-hole was going to crack open the planet, but this explanation would make a lot more sense.

• Very nice, haunting line:

  Liz: "Doctor, where did you go? Where did the TARDIS console take you?"
  Doctor: "Same time, same place... only a different dimension. It was a parallel world, Liz. Terrible things are happening there... terrible things. It wasn't this Earth, and... and yet it was. I didn't go backwards into the past, or forwards into the future, I... I slipped sideways."

• I like that the Doctor slips and calls the Brigadier "Brigade Leader", without even realizing it.

• Yet another good Doctor line:

  Doctor: "So free will is not an illusion, after all. The pattern can be changed."

• But, if you want to convince someone to come around to your way of thinking, taking an axe to their expensive computer equipment is possibly not the best way to go about it.

• One wonders why Stahlman needed to speed up his transformation. Wasn't he getting hairy fast enough? (Hrm, I nearly said "hairy palms". Insert own joke here, because I'm certainly not going to!)

• I'm not exactly sure that the attending crowd really understands the peril that the Earth will be in if this drilling succeeds. They all look very worried, but it's just plain worried without a hint of panic, so I'm not sure they really appreciate the situation! Perhaps if the Doctor had said "Penetrate the Earth's crust and you will be rewarded with a lava bath that boils the flesh off your bones and melts your eyeballs", then they would have listened properly.

• So, the drill bit gets stopped with 35 seconds to go. Better than 1 second, at least! But I still have to ask, how much of a barrier is that between the shaft and the center of the Earth? Wouldn't the pressure eventually crack it anyway? And will a concrete filling be stable enough to really keep the pressure from building and breaking the bore-hole open?

• Ouch, Doctor, nice job twisting the knife in the Brigadier's gut:

  Doctor: "Goodbye, Liz. I shall miss you, my dear."

• Another great delivery by Courtney:

  Liz: "Now see what you've done."
  Brigadier: "Well, I didn't know he'd go off like that. The man's so infernally touchy."

• Cute ending, and one last glimpse of dear laughing Liz... I shall miss her too! She's a great companion, and I wish they'd kept her around longer.

Total keeper. It's on the longer side, but still manages to be more engaging than most of Pertwee's other adventures. Worth watching for the steadily mounting tension of the parallel-universe scenes alone.