October 30: Enlightenment Parts Three & Four

The first two episodes of Enlightenment were set primarily on Striker's ship (the Shadow, according to the name on the lifebuoys), while the latter two split their time evenly between the Shadow and the Buccaneer, a 17th-century Spanish galleon.  Wrack, the captain of the Buccaneer, seems far more lively than any of the other Eternals we've seen -- but maybe that's because she's doing her best to emulate a pirate captain, as opposed to, say, Striker's English "stiff upper lip" approach.

However, the standout performance here has to be from Mark Strickson.  Turlough spends the entirety of these two episodes aboard Wrack's ship (well, once the Buccaneer scoops him up from his jump overboard), and he spends all that time being devious and conniving.  "Your mind is divided, confused, hard to read sometimes," Wrack tells Turlough, "but one thing is clear in it always.  Greed."  But Mark Strickson (who hasn't exactly started this story as the most subtle actor) turns it up in an extremely entertaining performance.  "I heard the power that speaks to you!  I heard it, and I know the voice," Turlough wheedles to Wrack, in an effort to save his neck.  "He speaks to me as well.  I serve him, as I wish to serve you."  It's tremendous fun, and it's a tribute to Strickson's abilities that, until the final moments of part four, you're never quite sure which side he's on.  Is he, for instance, actually betraying the Doctor in part four by claiming the Doctor's a spy?  Even though Turlough and the Doctor had a conversation about staying aboard the Buccaneer, and the fact that the Doctor seems sufficiently convinced by his intentions ("I think he wants to prove himself.  At least, I hope so," the Doctor tells Tegan), you're still not certain if he's going to side with the Doctor or the Black Guardian.

The Black Guardian and the White Guardian, ready to present
Enlightenment. (Enlightenment Part Four) ©BBC

But then these two episodes, at their heart, really are about Turlough, and while there are other incidents along the way (Tegan being frozen in time so that Wrack can plant a deadly jewel on her, the destruction of another vessel due to Wrack, Marriner's desire to be with Tegan -- "You are life itself," he tells Tegan.  "Without you I am nothing.  Don't you understand? ... I am empty.  You give me being.  I look into your mind and see life, energy, excitement.  I want them.  I want you.  Your thoughts should be my thoughts.  Your feelings, my feelings."  "Wait a minute," Tegan says.  "Are you trying to tell me you're in love?"  "Love?" responds Marriner, confused.  "What is love?¹²⁵  I want existence"), none of them are the focus of the story the way Turlough is.  And so the resolution ultimately comes down to him: as he helped sail the winning ship to the prize of Enlightenment, and as the Doctor isn't ready for Enlightenment, he's entitled to a piece of Enlightenment.  And thus Turlough is presented with a choice: does he take the diamond, as well as power and all the other things he would get from the Black Guardian, or does he spare the Doctor's life?  In the end he makes the right decision, giving the diamond to the Black Guardian, who disappears in flames:

WHITE GUARDIAN: Light destroys the dark.  I think you will find your contract terminated.
TURLOUGH: (discarding the now-blackened communication crystal into the fire) I never wanted the agreement in the first place.
DOCTOR: I believe you.
TEGAN: You're mad.
TURLOUGH: What I've said is true.
TEGAN: You believe him because he gave up Enlightenment for your sake.
DOCTOR: You're missing the point.  Enlightenment was not the diamond.  Enlightenment was the choice.

(from The Doctor Who Transcripts - Enlightenment)

Enlightenment brings an end to the Black Guardian trilogy, and while the White Guardian warns of a third encounter, to date this hasn't happened yet (unless Missy in series 8 is actually the Black Guardian...).  It's a satisfying conclusion, one that sparkles with energy and charm.  There's hardly a word or design choice out of place (well, except for the giant flashing VACUUM SHIELD OFF sign in Wrack's ion chamber, but I guess you can't have everything).  Imaginative and clever, Enlightenment is one of the best stories of the Davison era.







¹²⁵ Baby don't hurt me
Don't hurt me
No more

October 29: Enlightenment Parts One & Two

Well, it only took twenty years, but Doctor Who finally gets its first female writer for the show in the form of Barbara Clegg.  (Remember, by all accounts Lesley Scott did no actual work on The Ark.)  And so far, what she's written has been really wonderful indeed.  I like the slow build in part one, as the TARDIS arrives on a sailing ship that nevertheless has some oddities about it: the crew don't remember signing up, there are wetsuits for the crew, and the officers are decidedly peculiar.  And it's interesting how the officers are similar yet different from each other: none of them seem to be terribly good at understanding people, but where Captain Striker is incredibly calm and collected, First Officer Marriner comes off as incredibly creepy in his pursuit of Tegan.  Of course, they all seem to know what our heroes are thinking before being told, which might be extremely good anticipation or something else entirely.  And then it all leads into that gorgeous first cliffhanger, where we learn that this sailing ship is in fact a spaceship, racing against a number of other sailing ships from Earth's history through the blackness of space...

There are some great moments throughout these first two episodes, of which that first cliffhanger is only one.  There's also the interaction between the Doctor, Turlough, and the crew -- the crew's mistake of thinking the Doctor is in fact the ship's cook, and Turlough's cackling joy when the Doctor figures this out, is a particular highlight; the way the Doctor wants to finish his dessert before heading off after dinner; Turlough's decision not to kill the Doctor, in defiance of his deal with the Black Guardian ("I can't kill him!" Turlough cries), which leads to his desperate attempt to get off the ship, in the second cliffhanger, after the Black Guardian tells him he'll never leave Striker's ship; the nature of the Eternals, and their dependence upon Ephemerals -- those who live in one time and place -- and Striker's dismissal of the Time Lords ("Are there lords in such a small domain?"), even as he acknowledges that the Time Lords are more than mere Ephemerals; the way the scenes on deck are shot on film, suggesting location filming in an impossible locale...  Enlightenment is filled with things like this, which add to a sense of groundedness even as we're told this is an unreal situation.

So there's been some fabulous acting and some sterling writing, and the whole thing looks beautiful as well -- so kudos to director Fiona Cumming, designer Colin Green, and costumer Dinah Collin for their work on that front.  It's all especially impressive when you consider that this story was plagued by the same sort of industrial action that killed Shada and nearly ended The Invasion of Time.  The whole thing is beautiful and a joy to take in -- it'll be good to see what's in store for the final two episodes.

October 28: Terminus Parts Three & Four

In a way, you sort of feel bad for Janet Fielding and Mark Strickson; with one exception, their actions have no bearing on anything going on in the main plot -- it's as if writer Steve Gallagher didn't know what to do with Tegan and Turlough, and so shunted them off to do their own, not very exciting thing.  The only thing they do that's related to the main plot is when Turlough pulls some wires, trying to get the door to the TARDIS to reappear, and sends an electrical surge through the transport ship into Terminus, triggering an automatic fuel jettison.  Everything else they do is padding.  Mind you, there are some good moments in said padding: "If ever you had to kill someone, could you do it?  Could you?" Turlough asks Tegan thoughtfully at one point.  "No," Tegan replies.  "I don't know.  If it was important... to save my friend, to defend myself."  "But cold-bloodedly?" Turlough persists.  "You're weird, Turlough," she says.  "What a subject to bring up at a time like this."  Looks like Turlough is continuing to have second thoughts about his deal with the Black Guardian.

Terminus's dead pilot, the Doctor, and Kari in Terminus's control
room. (Terminus Part Three) ©BBC

Terminus's main storyline is content to move along without Tegan and Turlough, however, and it remains quite entertaining.  There are actually two storylines on Terminus itself: one involves the Doctor and Kari learning about the origins of Terminus, and the other is about Nyssa's treatment at the hands of the Vanir and the Garm, and Olvir's efforts to rescue her.  There's also another subplot regarding the leadership of the Vanir, and how they're in thrall to a faceless company that sends them drugs and patients, that neatly ties in with the Nyssa plot.  That Nyssa plot, involving her being cured of Lazar's disease, is more interesting for the way it shows us how Terminus is supposed to work than for any other reasons -- that said, the fight scenes are reasonably good and Sarah Sutton does a fine job of showing Nyssa in distress and then cured, with a new purpose in life as a result.

The Doctor's plotline has more of a bearing on events in terms of threat level, as he and Kari make some interesting discoveries about Terminus -- due in part to Bor, the Vanir who went into the Forbidden Zone in part one and made some unpleasant discoveries of his own.  Bor is probably the best of the all the Vanir, concerned far more with the possibility of another of Terminus's engines exploding than with anything else, including his own safety.  Of course, this means that he's contracted radiation sickness from being inside the Forbidden Zone so long -- "Short-term memory's the first to go," he tells the Doctor -- but he still remembers enough to tell the Doctor how to find the control room.

I really like the idea of Terminus being inadvertently responsible for the Big Bang by jettisoning its unstable fuel, leading to the explosion that created the universe -- and that's why Terminus appears to be at the exact center of the universe.¹²⁴  It's a "big" idea in an otherwise small-scale story, but it never feels out of place here.  In fact, it leads to some intriguing thoughts, which are never really explored but are still tantalizing to think about: if Terminus created the universe, what was there before?  Is the Garm from the original ship or was it brought aboard?  Plus it gives added impetus for the danger faced in the cliffhanger to part three and much of part four: if the jettisoned fuel the first time around was enough to create the universe, jettisoning the fuel a second time would be powerful enough to end everything.

But while there are big ideas driving the plot, the resolution is ultimately on a personal level; the Vanir wish to be free of the company and run Terminus on their own; the Garm is willing to save the universe in exchange for its freedom (to put it crudely); and Nyssa is cured and wants to help.  This last one is the big one, because it means that Nyssa has decided to leave the TARDIS.  Tegan is, predictably, unhappy about this ("She'll die here," Tegan says), but the Doctor seems accepting of the decision -- and, rather sweetly, Nyssa gives him a farewell kiss on the cheek.

Terminus is a story that often gets a lot of grief from fandom, but it's honestly hard to see why.  There are a few questionable moments here and there, and some design decisions that don't work, but the core of the story is solid, and there are a lot of entertaining parts to a well-written script -- and one that seems to have had most of its plot bugs worked out ahead of time (not always the case at this point in the show's history).  It's a story that strikes a fine balance between big ideas and small interpersonal relationships, and it does so in a suitably compelling fashion.  Something of an overlooked gem, then.







¹²⁴ That said, I know that the Big Bang wasn't an actual explosion and that the universe doesn't actually have a center.  But it's still a nice big idea.

October 27: Terminus Parts One & Two

Nope, looks like Turlough is still working with the Black Guardian -- and the cracked crystal has been repaired too.  Tegan is still incredibly suspicious and distrustful of Turlough, although again there doesn't seem to be a good reason for it beyond "hey, Turlough's working for the villain, so someone has to be against him."  It's not very satisfying as a result, and it doesn't make Tegan come off very well.

But it's actually Turlough's efforts to destroy the TARDIS ("I am ready to lift you away," the Black Guardian tells Turlough -- the words "yeah, right" come to mind) that lead to the main storyline, as the TARDIS latches onto a nearby spaceship to save itself from breaking up.  Nyssa heads through the doorway that appears, and the rest of the story so far is about what she and the Doctor discover.  (Tegan and Turlough spend the end of part one and all of part two trapped in some ductwork beneath the floors of the ship.  It's about as thrilling as it sounds.)

I do like the slow realization, near the end of part one, that this ship isn't simply carrying standard cargo, but instead plague victims, and so the two raiders, Kari and Olvir, learn not only that they've been abandoned on a ship by their captain, but that it's a ship full of diseased people.  Or, as Olvir memorably puts it at the end of part one: "This is Terminus!  Where all the Lazars come to die. We're on a leper ship! We're all going to diiiiiiie!!!"  And we learn in part two that Nyssa has also contracted the disease and is thus forcibly separated from the others.

Of course, it turns out that there are other people aboard Terminus.  The ones looking after the Lazars are the Vanir -- but rather than being like the Norse gods of their namesake, these people are a sickly lot, dependent on a drug called hydromel and looking little better than the patients they're handling.  I do like the look of their armor though, with its skeletal motif -- but there are also some small little touches (a snake head here, a dragon there) that add some character to the look.  And people tend to look down on the Garm, but, glowing red eyes aside, I've always found it to be a reasonably convincing character.  The Garm is certainly imposing; it's huge in every direction, and the idea of its being a servant of the weak-looking Vanir suggests that they must have some hidden strengths.  And we get to find that out in part two's cliffhanger, as one of the Vanir attempts to throttle the Doctor -- with hands around the throat this time, rather than the usual Shoulder Rub of Doom.

There are other nice touches scattered throughout these two episodes; the skull motif on the transport ship, the transparent colored blocks that represent computer chips (rather than the standard "bits of circuitry" we usually get around this time), and all the different colored strips that show that the Forbidden Zone has been slowly getting larger (presumably as the radiation contamination increases).  It's been a slow build, but thus far Terminus has been an intriguing story.

October 26: Mawdryn Undead Parts Three & Four

The two Brigadiers just avoid meeting each other. (Mawdryn
Undead Part Three) ©BBC

While the first two parts of Mawdryn Undead were interested more in the interwoven timelines, these two episodes are concerned more with the idea of assisted suicide, filtered through an SF lens.  Of course, it takes a bit of time to get to that point (since it ends up being the cliffhanger to part three -- "It would be the end of me as a Time Lord!" the Doctor exclaims upon hearing of Mawdryn's wish for the Doctor's help in letting them die), and so part three is filled with a decent amount of wandering the luxury spaceship, combined with some more attempts by Mawdryn to convince Tegan, Nyssa, and the '77 Brigadier that he's the Doctor (even though we the audience know he's not).  It's entertaining, but it's not, strictly speaking, doing much in the way of plot advancement.  We learn that Mawdryn has seven compatriots on board, and that Turlough is still doing the Black Guardian's bidding (although he seems quite reluctant to actually kill the Doctor; most of his plans seem to involve trying to strand him instead), and that there are two Brigadiers on board, and should they meet, the result will be catastrophic.  And that's really about it.

Part four deals more with the assisted suicide subplot, albeit in a manner which coerces the Doctor into helping them; he's not particularly keen on giving up his remaining regenerations to free Mawdryn and his fellows from their unending regeneration cycle (which they're suffering from thanks to some pilfered Gallifreyan technology), but when it turns out Nyssa and Tegan are infected with the same problem as Mawdryn, the Doctor feels he has little choice but to grant the poor fellows their wish.  It's not a situation that's explored with any complexity, but the fact that they're even bringing up euthanasia at all is somewhat surprising.  Of course, thanks to a deus ex machina (the two Brigadiers meeting at exactly the right moment, shorting out the time differential and supplying the power needed to cure Nyssa and Tegan and end the eight travellers' lives -- this event, incidentally, is why the '83 Brigadier had amnesia at the beginning of the story) everyone gets what they want without the Doctor no longer being a Time Lord, but it's interesting that the Doctor was willing to go through with it -- and it's nice that Tegan thanks him for that.  And although Turlough was unable to kill or strand the Doctor, he's apparently going to get another chance, as he joins the TARDIS crew at the end of the story (although there's the moment where Turlough discovers that his Black Guardian communication crystal is cracked -- is he free of the Black Guardian's influence now?).

On the whole, Mawdryn Undead is a success.  It's nice to have such a small stakes story (it's not the universe at risk, it's just eight people with a simple request), and there's enough going on otherwise (the return of the Brigadier, the Black Guardian's delayed revenge over the events of 1978's The Armageddon Factor, the mingling of the two time periods) to keep the audience happily entertained.  Even the inclusion of the Brigadier feels right, even if he is a maths teacher -- the story originally called for Ian Chesterton to be the returning character, but the Brigadier slots in surprisingly well.  It's not a "big" story, but it's not trying to be (as opposed to, say, Arc of Infinity, which does want to be a "big" story but fails at it).  There may be a section of fandom who wish this story had never happened (albeit for the wrong reasons¹²³), but they can be safely ignored.  Mawdryn Undead is a charming tale.







¹²³ All right, let's tackle the big one: assigning dates to the UNIT stories.
     When the UNIT stories were first conceived, the assumption was that they were taking place some 5-10 years in the future.  So The Invasion was supposed to be 1975 (at least, according to the continuity announcer before Episode 1), Spearhead from Space 1976 or so, and so on -- hence Sarah Jane's otherwise bewildering comment in Pyramids of Mars about being from 1980.  However, while this may have been the guiding philosophy of the production team, it's never actually stated anywhere in the programme proper (Pyramids of Mars aside), and there are enough hints in the broadcast episodes to suggest an earlier '70s date (i.e., 1-2 years in the future) -- although, again, nothing definitive, and there's sufficient leeway to keep both sides happy.
     The real problem comes with Mawdryn Undead.  By 1983, the UNIT stories were already looking a bit vintage and thus were more or less placed in the "early '70s" category in the view of the contemporary production team -- and so this story has the Brigadier retired by 1976 and teaching at a public school, even though that contradicts the "late '70s" approach that the Pertwee team was going for.  For some reason, even though the year is explicitly and repeatedly stated on-screen in Mawdryn Undead, this is still a hugely controversial issue in some circles, and some fans are incredibly unwilling to go against the Letts' team's original intentions, despite the on-screen evidence -- to the point that they're still making jokes about it (see, among others, 2008's "The Sontaran Stratagem" and 2013's "The Day of the Doctor").
     (Although while they're making jokes about it, nevertheless things like The Sarah Jane Adventures (explicitly in the same continuity as Doctor Who) are going around reinforcing the early '70s dating -- see, for instance, the SJA episode "Whatever Happened to Sarah Jane?", which establishes that Sarah was thirteen in 1964, and then note that she gives her age as 23 in Invasion of the Dinosaurs.)
     However, looking at the evidence objectively, it's pretty clear that placing the Pertwee stories in the early '70s works without any real insurmountable problems (or, at least, without any problems that aren't also confronted by late '70s dating -- the British Space Programme doesn't really fit with either time period), while going with late '70s dating requires you not only to pretend Mawdryn Undead never happened, but also to believe that a number of real world events (e.g., Britain switching to decimal currency and the death of Mao Zedong) happened differently in the Doctor Who continuity.  In short, early '70s dating simply makes more sense, and we can move on to something more productive, like trying to work out when the Russell T Davies stories are actually set.

October 25: Mawdryn Undead Parts One & Two

It opens with a really bratty schoolboy named Turlough who goes around endangering others and generally not caring about if he lives or dies.  "I don't think I'd really care if I were [dead]," he says after getting in an accident and looking down on the scene, in an unbelievably early '80s computer-generated vortex.  He's there courtesy of the Black Guardian, who wants Turlough to kill the Doctor -- "one of the most evil creatures in the universe," the Guardian tells Turlough -- and in exchange the Black Guardian will take Turlough away from Earth (Turlough's not a native, it seems).  Oh, and it seems that the maths teacher at Turlough's public school¹²² is one Brigadier Alastair Gordon Lethbridge-Stewart, last seen in 1975's Terror of the Zygons and now retired from UNIT.

Into this somewhat unusual setup the TARDIS arrives, caught in a warp ellipse along with some sort of luxury spaceship.  The warp ellipse has immobilized the TARDIS, so while Turlough is being manipulated by the Black Guardian into a position near the Doctor, the Doctor himself (now apparently sporting mini-mutton chop sideburns) is trying to locate the ship's transmat beam (last operated six years earlier) so that the TARDIS can leave.

Turlough's introduction to the Doctor is pretty great, by the way; he enters the TARDIS while the others are out, and while he's checking out the TARDIS the Doctor rushes in, before looking slowly at Turlough.  The Doctor seems quite willing to trust Turlough; Tegan doesn't, although there doesn't seem to be any reason for her not to.  "Nobody from Earth is just going to walk into a transmat capsule," she complains.  "As you did into the TARDIS on the Barnet bypass?" Nyssa asks pointedly.  Of course, in this case Tegan is right (not that she knows that), and after the Doctor releases the transmat beam down on 1983 Earth, the TARDIS briefly materializes and then is gone again, and while the Doctor tries to figure out what went wrong, Turlough lifts a big rock and prepares to kill the Doctor.  "In the name of all that is evil, the Black Guardian orders you to destroy him now!" the Black Guardian cries, which rather ruins the whole "you're doing the universe a favor by killing an evil man" excuse. 

Part two is primarily about three things: first, the Doctor's renewed relationship with the Brigadier; second, the badly injured Doctor that Tegan and Nyssa find; and third, the storylines in the two different timelines (1983, where the Doctor is, and 1977, where Tegan and Nyssa are).  That first thing is handled rather well; I like the idea of an amnesiac Brigadier who doesn't remember the Doctor or any of his friends or the events he shared (so, what did he think he did at UNIT all those years?), and the way in which the Doctor lifts the Brigadier's mental block is quite lovely, with all those sepia-tinted memories flooding back.  I also like the way the subsequent storyline ties in with the third point, with us seeing what Tegan's doing with the 1977 Brigadier (quickly identifiable by the moustache he's sporting that the '83 version lacks) at the same time the 1983 Brigadier remembers what happened and tells the Doctor about it.

That second point is less successful; does anyone buy that that's supposed to be the Doctor?  (Mind you, my wife bought it...for about fifteen seconds, by her reckoning.)  It's more entertaining how the not-actually-Doctor (as played by David Collings) leaves smears of the body paint he's wearing everywhere -- and if you look, you can see Janet Fielding's hands are just covered with the stuff after she drags him inside the TARDIS.  But even though it's less successful, it ends up being the driving force behind much of the episode, and while we learn that he's actually Mawdryn, not the Doctor (thus explaining the story's title), there's also some intriguing stuff about him becoming a Time Lord.  And his appearance at the end of the episode, when the '77 Brig enters the TARDIS, is quite horrific, with his pulsing exposed brain...








¹²² Remember, in England a public school is, somewhat confusingly, a type of private school.

October 24: Snakedance Parts Three & Four

The Doctor and Nyssa discuss the Little Mind's Eye crystal.
(Snakedance Part Three) ©BBC

One of the impressive things about part three is that this is the episode where the Doctor works out the backstory of the Mara -- despite being locked in a cell for the majority of the episode -- through a combination of Dojjen's journal (the previous director's, given to the Doctor by Ambril's assistant Chela) and Nyssa's working through the properties of the crystal -- concluding that it must be man-made with no imperfections of any kind (not even distortions from gravity), an incredibly advanced technique from a people who now appear to be too primitive to be able to perform it.  Therefore, the Manussans were once very advanced, but when they made the Great Crystal (aka the Great Mind's Eye) in order to harness their mental powers, they brought the Mara into being, leading to the downfall of their civilization and the rise of the Sumaran Empire.

Of course, while the Doctor and Nyssa are locked up, the Mara is making plans for its return.  Curiously, though Lon is clearly in the thrall of the Mara, he still seems to retain some semblance of his old self (unlike Tegan), and while he's being controlled by the Mara, it's not actually living inside him.  But he's fascinatingly manipulative with Ambril, who ultimately seems willing to let Lon use the Great Crystal during the Defeat of the Mara Ceremony, even though a) it's expressly forbidden, and b) he's seen some weird stuff inside the cave full of artifacts -- like Dugdale doing his barker routine to no one in particular.  Incidentally, it's the "expressly forbidden" part that seems to convince Chela to release the Doctor, who's the only one who's been warning of dangers while Ambril is continually dismissive of the possibility.  And incidentally, I really like the incorporation of the Mara into the Punch and Judy show -- it's a really nice touch.

Part four has two moments that are really wonderful.  The first is the Doctor's interaction with Dojjen, who's gone off into the hills to become a snakedancer.  The telepathic conversation they share (thanks, it seems, to a snake bite) is enigmatic and charming, with some great lines, such as "Fear is the only poison" and "The still point is within yourself ... To destroy the Mara you must find the still point."  I also like how the Doctor takes full responsibility for Tegan having succumbed to the Mara; it's a nice touch.

The second moment is the ceremony itself; there's something pleasingly elegant about the (obviously well-known) lines spoken during it: "I offer you fear in a handful of dust", "I offer you despair in a withered branch", and so forth.  Plus, the way in which Lon causes the ceremony to go off the rails is really well done ("What do you mean, [the crystal has] hidden depths?  Where are they?  Show them to me.  It's just a fake.  Your whole ceremony is a fake"), and the reveal of the Mara is a lot better than it was in Kinda.  It's a significantly more convincing snake.  The defeat of the Mara here is also better than it was in Kinda -- there's nothing here about mirrors, but instead it's about one man's refusal (the Doctor's) to submit to fear, to instead find the still point inside and thus disrupt the Mara's power.

Snakedance is a much more accessible story than Kinda was, and I think that's a real strength, for while Kinda was fascinating in its use of metaphors and imagery, Snakedance has much of the same feel while telling a more coherent tale.  There are also some brave elements to this story (making the Doctor seem like a crazy outsider, for instance), and the whole thing coheres thanks to the sterling directorial work of Fiona Cumming.  I've already mentioned the excellent work that Martin Clunes and John Carson have put into this, but I haven't mentioned Janet Fielding, who finally gets a chance to really let loose as the possessed Tegan.  It's a frightening performance (even more so because we're familiar with how Tegan usually is) and one that Fielding takes full advantage of.  All this and a great script make Snakedance easily one of the standouts so far of Peter Davison's tenure.