Then there's “The Tholian Web”, which is just about made of iconic moments.
Right from the start we have what amounts to a ghost starship, which is a concept so fundamentally and basically wrong the Enterprise's own sensors refuse to accept it's there. Beaming aboard, Kirk, Spock, McCoy and Chekov find the entire crew dead, apparently at their own hands. While it's never explicitly stated this time, the Defiant bears all the symptoms of what could be called a dead starship, and when those show up it's usually the sign something very big and very serious is about to go down. Indeed, the Defiant takes this theme to the next level: If a starship can die, a starship can become a ghost as well, and it can also haunt. And this is very clearly what the interspatial rift is: It's a haunted region of space where weird, unexpected and incomprehensible things happen. This was even more blatant in Judy Burns' original script, which also featured cosmic spirits manifesting in space and fading in and out of existence onboard the Enterprise. However, as Gene Roddenberry didn't like the supernatural and had specified as much in his writer's guide for Star Trek, this plot point was altered somewhat in the produced episode.
But even so enough of this remains in “The Tholian Web”, and the episode we get is still extremely eery and atmospheric. What clinches it is when the Enterprise is attacked by Commander Loskene and the Defiant fades out of normal spacetime. Kirk had stayed behind when the initial landing party was forced to return as the transporter was only able to beam back three at a time, thus becoming trapped onboard the departing Defiant, and is declared dead by Spock. From this point onward, Kirk becomes a ghost himself, and he haunts the remainder of the episode on a number of levels. First, his absence understandably causes great strain on the crew, particularly Spock and McCoy. Without Kirk to mediate between them, their normally quasi-friendly banter becomes openly hostile, each clearly resenting the other's presence. This could be interpreted as evidence of the old reading of Star Trek that posits Kirk, Spock and McCoy represent the tension and interaction of the id, ego and superego, but I still disagree with that pretty vehemently. For one, that's actually not how the actors are playing these characters: DeForest Kelley shows McCoy's barely restrained distrust of Spock unleashed and free to go wild. Leonard Nimoy, by contrast, returns to the style of performance that made him famous by playing Spock as someone *trying* to be logical and collected but who is in truth plagued by self-doubt and second guessing. These are very personal moments that come expressly out of who these characters are, not some phony and tacked-on bit of pop Freudianism.
(My favourite scene in this regard is at Kirk's memorial service where Spock tells the crew that he cannot put into words what made Kirk a good man, and that each person individually must look inside themselves to figure out what Kirk meant to them personally. It's a very, very Spock thing to say and a very Nimoy moment: It's as much a confession and an apology as it is an appeal to individual positionality and experience, although Nimoy is, as usual, best at conveying this via subtle nonverbal cues).
But Kirk also acts as a literal ghost, as he starts appearing to various crewmembers culminating with a full manifestation on the bridge in front of Spock, McCoy and Scott. This is actually handled exceptionally well; Uhura is the first to see him, and she's at first dismissed as suffering hallucinations brought upon by the interspatial rift, which by this point has been revealed as the source of a kind of madness that causes crazed, violent outbursts and what killed the Defiant. But, once Scotty sees Kirk too, and then the entire bridge, Uhura is vindicated, and the episode even goes out of its way to give us a scene where McCoy undoes Uhura's restraints and tells her that no, she's not crazy: The captain is very much alive. I really like this scene because, were this just about any other show, that whole exchange would have been totally skipped, or at least briefly acknowledged with a throwaway line. We'd cut back to the action, rescue Kirk and Uhura would be back on the bridge for our “everybody laughs” denouement as if nothing had happened. I hate it when shows do this (and almost every show has at one point or another), leaving what really need to be important, intimate character moments to our imaginations. But Star Trek makes sure we get to see that, because it, at least for right now, knows these characters are people and deserve to be treated with respect and dignity, especially as each and every one is somebody's inspiration or role model.
(And Nichelle Nichols looks positively elated, not just for her character, but to be doing this scene at all. It's little wonder she names this one of her two favourite episodes).
This peculiar otherworldly feeling is present elsewhere in “The Tholian Web” as well. There are, of course, the Tholians themselves, who have always been one of my absolute favourite alien species in all of Star Trek. Commander Loskene (who is referred to as a “he” in the episode but always came across to me as quite feminine, especially voiced by Barbara Babcock) just looks plain weird: In one of the best uses of the Original Series' gaudy primary colours, Loskene appears as an overly exposed glowing red geometric shape afloat in a swirling blue haze. She looks nothing like any other Star Trek alien we've ever seen before, and with just a crudely defined head and a bizarre energy web, our imaginations are racing to conceive of what these creatures might actually be like. It's yet another vividly memorable image that draws you right into both the show's world and it's mood. Indeed, one of the savviest moves Enterprise ever made was, when they did a pseudo-sequel to this episode and needed to show a full-bodied Tholian, depicted them pretty much exactly the way you'd expect them to look: As giant, burning, psychedelic crystalline polygon crab-spider things.
I don't use the term “otherworldly” here at all lightly: “The Tholian Web” is very much about an Otherworld in the pre-Christian heathen sense. Most obviously, there's the ghost ship Defiant and Kirk's passing into the region beyond the interspatial rift (itself a magickal doorway, much like the barrows, or sídhe, might be in CelticXNordicXGermanic mythology). But also there's the Tholians-Not only does Loskene not look like any alien we've seen before, she doesn't act like one either. She appears out of nowhere, threatens Spock and then ensnares the Enterprise in a perfectly geometric spider web for ultimately unknowable reasons. Although it's not made explicit, to me, the implication is that the Tholians are very clearly meant to be inhabitants of the Otherworld here, who have always been portrayed as creatures who operate by a standard of logic and morals that are completely impossible for us to fully understand. This would also explain the Tholians' aggressive territoriality: Typically visitors to the Otherworld from our plane are only welcome if they're explicitly asked to visit, and the Enterprise has shown up someplace it's not supposed to be without an invitation (and also note again how psychedelic Loskene looks and the reappearance of that fisheye lens, used here in the PoV shots of the crewmen under the influence of interspace) .
What's really exciting though is how Burns melds this concept with science fiction. Firstly, Spock gets this extremely telling bit of dialogue:
Well, picture it this way, Mister Chekov. We exist in a universe which co-exists with a multitude of others in the same physical space. At certain brief periods of time, an area of their space overlaps an area of ours. That is a time of interphase, during which we can connect with the Defiant's universe.
This is exactly how the Otherworld is supposed to work, especially in the CelticXNordicXGermanic tradition. The way Spock describes the “time of interphase” is word-for-word precisely what happens during the festivals of Beltane, Mittumaarin and Samhain: The boundaries between worlds becomes permeable and can be freely crossed. With that in mind, it's also interesting that it's Shatner-as-Kirk who not only gets to spend the majority of the episode on the other end of the looking-glass, but gets to come back as well. Sure, he says the universe he wound up in was “completely empty” when we might expect it to be full of Tholians or some similar kind of space spirit, but we can also attribute this to the Nordic concept of the Nine Worlds: The Eddas describe not just one Otherworld, but eight, unified by the World-Tree Yggdrasill. Even Celtic lore occasionally makes reference to there being more then one spirit world or Land of Eternal Summer. And, of course, Spock mentions a “multitude” of other universes. So Kirk just managed to find himself in a pretty boring Otherworld then.
But the real coup de grace, although probably not explicitly intended by Burns, is that the Otherworld of “The Tholian Web” isn't just a CelticXNordicXGermanic one, though it definitely draws quite heavily on that tradition: It's also a Polynesian one. It is firstly, as I mentioned above, overtly a Land of the Dead: The Defiant is most definitely dead and Kirk acts like a ghost when he's on the other side (which might even explain the puzzling rapidity with which Spock declared Kirk killed in action). The Polynesians also believed in the idea of multiple worlds, typically divided into the realms of the Sea, Earth and Sky. In some variants of Polynesian mythology, one of the places the deceased might go is the world of the sky. So now we have not only an Otherworld situated in outer space, previously only the domain of “serious” science fiction, but the vaguest hint that maybe Star Trek is itself some kind of Otherworld as our heroes inhabit the sky world already, even without needing to cross the interspatial rift. This actually makes perfect sense for a series moving more towards utopianism: The show embodies ideals we might not actually be capable of living up to, but it remains a powerful source of inspiration and hope. It's in many ways then an Otherworld of fiction and oral myth, perhaps even an...“ideaspace”...but now I'm getting ahead of myself.
What's really the most important about “The Tholian Web” for me is that it shows Star Trek on the vanguard of a major sociocultural transition that's about to take place. Star Trek began, of course, firmly in both the Golden Age and pulp science fiction traditions, but had the unenviable misfortune to come out just as both genres were beginning to wind down. The cutoff point is often put at the Apollo 11 mission, which supposedly turned the public perception of outer space away from something that was our inevitable destiny and a place where weird, unusual and exciting adventures could happen to that of a vast, cold and most likely empty void. This, the argument goes, proved to be the death knell of Star Trek's kind of science fiction. But I don't think even the original Star Trek was as indebted to Golden Age Sci-fi and pulp as much as that argument needs it to be: Certainly Gene Coon and Robert Bloch at least might have some objections to voice about that.
More to the point though, both Golden Age and pulp sci-fi emerged were at their peak alongside the UFO era. Kenneth Arnold's famous “flying saucer” sighting over Mount Rainier on June 24, 1948 put the idea of hyper-advanced extraterrestrials visiting Earth in snazzy spaceships firmly into the public consciousness. Although, as Jacques Vallée points out, sightings of mysterious objects in the sky have been around for almost the entirety of recorded human history, the specific theory they are alien spacecraft is an invention of the mid-20th Century. In many ways the UFO era and sci-fi of the Golden Age and pulp variety are intertwined, and while neither UFOs nor science fiction ever go away, there is a kind of shift in the way both are read after this point. As this kind of science fiction fades away, so does the classic UFO era, to be replaced in the 1970s with what might be called a more overtly Fortean era of inexplicata that draws much more heavily on indigenous spirituality and mysticism (although Forteanism, like the UFO phenomena, has also been around as long as people the true beginnings of this particular era are really with John Keel and the pointedly bizarre happenings in Point Pleasant, West Virginia in 1966, appealingly synchronously around the same time Star Trek went to series).
This is ultimately more the domain of something like Scooby-Doo, especially right now, and there's in fact a truly magnificent episode of Scooby-Doo, Where Are You! that will air about a year from now that is the definitive statement on the death of the UFO era and first-wave science fiction. But “The Tholian Web” is about this too, with its Space Land of the Dead and overtly mystical overtones. The fact Star Trek can do an episode like this and have it not seem at all out of place is proof positive the franchise is something more than the sum of its parts, and this is yet another reason it has the ability to last forever. The Enterprise has learned how to travel between worlds, and it now has everything it needs to transcend itself to seek enlightenment.
Of course Judy Burns had to be a fan.