The following contains SPOILERS to Doctor Who‘s Series 10 finale. Please watch before reading.

It’s been a funny ol’ series of Doctor Who. A couple of weeks ago I wrote about how sort of off it began feeling following its first five enjoyably throwback-y episodes. Still things turned around dramatically with “World Enough and Time” and the cliffhanger of Bill Potts being turned into a legitimate Mondasian Cyberman was chilling. Now, with the finale of Series 10, we were treated to an episode all about the march of time being completely unconcerned with what people might want. “The Doctor Falls” is a decidedly downbeat title and the episode bore that out, in a satisfying way.

At a certain point–and maybe it should have been sooner–I realized that “The Doctor Falls” was a western. Like Rio Bravo or Shane, it ended up being about a small group of people, and one man at the heart of it, trying to preserve some semblance of decency in an otherwise chaotic, lawless world. Actually, I think a better comparison would be The Wild Bunch or Bring Me the Head of Alfredo Garcia, because the Doctor’s willingness to head off to his own doom is completely unfettered by whether or not he’ll actually succeed. To drive the point home, some of Murray Gold’s score has a Degüello, or a bugle call traditional in Mexican culture, and used in westerns a lot, to signify impending death.

We open with a bit of a sped-up reveal that the two Masters have knocked out the Doctor and have turned the entirety of the bottom floor of the 400-mile-long spaceship into a Cybermen foundry. But the Doctor has made it so they’re looking for two-hearted individuals. So they have to run. Bill has become a Cybermen, but she still retains her inherent Bill-ness, which is unique among Cybermen for…oh, just about every reason. And because of the march of time within the spaceship, they can’t just go back up to the top to get the TARDIS, because the Cybermen will have had thousands of years to evolve. So the Doctor and company have to plant on one of the faux-pastureland floors of the spaceship and defend it.

“The Doctor Falls” is perhaps one of the most thematically consistent episodes I’ve ever seen. Writer Steven Moffat has chosen essentially “Change is Coming” as his central thesis here–owing of course to the complete change of everything following the Christmas special–and he shows us how each of the five principle characters deals with this. Nardole has it the easiest; his change is simply that he can’t stand by the Doctor, or even stay behind and sacrifice himself so that the Doctor can live. Nardole is stronger than the Doctor, and therefore he’ll have to stay with the people, defending them, several floors higher, from any Cybermen attack that might come in the future. His change is stationary.

Bill has a much stranger and altogether more tragic outcome. She’s a Cyberman, but with feelings and memories, and people are afraid of her simply because, well, she’s a Cyberman. So she truly cannot stay in this state forever. She is indistinguishable at a glance from any other Cyberman, so the townsfolk can’t trust her, as evidenced by the moment of her getting shot accidentally by the startled woman in the house. Bill has chosen death over this life, and death beside the Doctor…which she ultimately doesn’t get.

I did think that Bill’s salvation–I truly would have been very upset if she just remained a Cyberman forever [sidebar: Moffat is sure obsessed with turning characters into Cybermen, huh? He’s turned Danny Pink, the Brigadier, and now Bill all into Cybermen. Dude.]–ended up being a bit convenient. The sentient oil woman from “The Pilot” shows up, after the Doctor is dead on the battlefield, and Bill is still Cyber-alive, and turns her…soul, I guess(?) into an oil person just like her. She also brings the Doctor back to the TARDIS, and Bill even reignites the Doctor’s lifesigns, triggering again his regeneration. It sort of just felt like Bill’s ending was the romantic equivalent of Clara going off in the TARDIS with Lady Me at the end of Series 9. But it was a change, and a fairly happy one, all things considered.

Now we move on to the Masters. One thing Moffat did very nicely in this episode was explore what the dynamic between two versions of an evil character would be. We’ve seen many times that multiple Doctors would argue with himself a lot, because the Doctor is nothing if not totally self-loathing. But the Master is an egotist and so not only gets along great with a version of himself; he actively flirts. Is it incest or masturbation? Luckily, we’ll never have to know that. John Simm’s Master represents the never-changing, never-faltering hatred that every Master from 1977 forward had, whereas in Michelle Gomez’s Missy, we see a lot of the begrudging respect and sometimes allegiance that the original Roger Delgado Master possessed.

And so, after the Doctor’s impassioned speech to the Masters about it not being about winning but about doing the right thing, about being kind, we know that the Simm is the Master who would never listen, but that Gomez is the Master who might. Rather than escaping together, Missy stabs her former self, which would send him off to regenerate into her, presumably. She says she needs to stand by the Doctor, this once. She’s changed, even if not forever. But, ever the agent of stagnancy, Simm’s Master cannot accept that “he” would ever stand with the Doctor and laser-blasts Missy to the point of blocking regeneration. The pair laugh together as they ultimately each go on to their death. “Shooting yourself in the back” is their end, and it evidently cannot be changed.

The Doctor also, weirdly, seemed totally unprepared for change. He got shot by Cybermen real bad but staved off his regeneration in order to blow up with the Cybermen, which he does. But when Bill reignites his life, and he begins to regenerate, he doesn’t want it. We see all of his previous companions saying “Doctor,” and even Missy saying it–this was a great reference to “Logopolis,” the final story of Tom Baker–and he wakes up and says Tennant’s final line “I don’t wanna go” and Smith’s final line “I’ll always remember when the Doctor was me” but then refuses to allow regeneration to happen. This is the end, this is how he’ll be, live or die.

But, obviously we know that change is inevitable. Peter Capaldi is leaving at Christmas, as is showrunner Steven Moffat, after what will be his sixth series at the helm. But whereas the Russell T. Davies ended with that abhorrently petulant final line from the Tenth Doctor, the Moffat era seems destined to end with a realization that change is necessary. The Doctor, fighting off regeneration, finds himself in a snowy somewhere, muttering about change, only to discover someone else doing the same thing…not just A Doctor, but THE Doctor. “The original you might say.” Yes, through the First Doctor (guest star David Bradley), perhaps they’ll both see that without change, it’s just death.

I love the implication of this final scene, and having both of the “oldest” Doctors on screen together will be magical come Christmastime. I’m guessing there’ll be a lot of tears, and I’d be very surprised if Clara doesn’t return (she’s going to, which is why I would be surprised if she didn’t).

As a finale to Series 10, “The Doctor Falls” seemed incredibly dour, but as a precursor to the end of a Doctor and a showrunner’s time, it seems oddly hopeful. We’ll have to wait until Christmas, but as the episode proved, the march of time will continue whether we’re ready for it or not.

Images: BBC America

Kyle Anderson is the Associate Editor and the resident Whovian for Nerdist. Follow him on Twitter!