In the Doctor Who season 10 finale, Peter Capaldi prepares for a grand exit, as the Doctor is pitted against Missy and the Master.

This isn't your usual season finale of Doctor Who by any stretch of the imagination. There's a great big unknown on the other side of 'The Doctor Falls' that – Christmas Special notwithstanding – is due to deliver a dramatically different show, practically from top to bottom. With a new actor in the role of the Doctor and Broadchurch's Chris Chibnall stepping in to replace outgoing showrunner Steven Moffat, it promises the kind of creative shakeup Doctor Who is in need of – on paper at least. With so many major parts being replaced at once, the incoming change is poised to be a dramatic one the likes of which might even eclipse the handoff from Russell T. Davies to Moffat that led to the show being what it currently is.

Still, before anyone starts looking too far into the future and wondering who will be the Doctor post-regeneration, there's still the matter of season 10 to worry about. Last anyone saw, Bill had been conscripted into the ranks of the Mondovian Cybermen and John Simm's the Master revealed himself to the Doctor and before that… himself. That self, of course, is Missy who appeared to have turned over a new leaf – or was at least seemed committed to trying to turn over a new leaf – before running into her past self in disguise (it's almost scary that this is easy to follow) and seemingly siding with the Master as he points out the Doctor, Nardole, and Bill have inadvertently stumbled on the "genesis of the Cybermen."

As far as Doctor Who scenarios go, 'World Enough & Time' and 'The Doctor Falls' are perhaps two of the Doctor Who-iest hours of television the series has put forth all season long. And with the promise of regeneration right around the corner – as evidenced by last week's cold open – there are some fairly high expectations set upon this season 10 finale.

Michelle Gomez and John Simm in Doctor Who Season 10 Finale

Moffat and director Rachel Talalay had set quite the table last week by putting Bill and (who would be revealed as) the Master on a 10-year wait list to see the Doctor, only to have Bill wind up becoming a Cyberman mere hours before his arrival. The scenario becomes one of those quirks of timing that sometimes plays out as too ironic considering the Doctor's relationship with time, but the immediacy of Bill's condition mixed with the encroaching Cybermen army and, of course, double the Master (double the fun) the finale manages to elicit more emotion from the circumstances than might otherwise seem possible with that many balls in the air.

Last week it seemed like Doctor Who might have been overplaying its hand with its snowy opening sequence, but now, knowing the Doctor's regeneration is right around the corner actually works in the finale's favor. There is so much ground to cover in 'The Doctor Falls' that, even running longer than the usual hour, it would have been a disservice to the story at hand and to the characters, like Bill and Missy, who ostensibly said their goodbyes, had the issue of regeneration not been crossed off the To Do list ahead of time. The effect, then, is an episode that can devote more of its time to the question of Bill and Missy.

With the amount of attention the vault received at the start of the season, there was some expectation that its occupant would have played a more prominent role in overarching narrative. As the season went on, neither the vault nor the idea of the Doctor's oath really paid off in any meaningful way. Instead, both felt like more of a device to connect the Doctor to Missy and to legitimize her arc toward the end of the season. The series' interest in the question of whether or not the Master could change wasn't really serviced enough over the course of these past 13 episodes for it to have mattered as much as perhaps Moffat was intending with this finale. And yet, because of Michelle Gomez's performance, and her delightful pairing with Simm, Missy's efforts to change weren't entirely fruitless. Doctor Who takes a shortcut in bringing the Master's story full circle by bringing Simm back to offer the audience a before and after. Gomez wonderfully expresses Missy's struggle and externalizes what is essentially an internal conflict in a way that only makes sense in this series, so that when the Master kills Missy, after she sets into motion his regeneration into her, the arc winds up feeling emotionally satisfying if not entirely complete.

Peter Capaldi and John Simm in Doctor Who Season 10 Finale

'The Doctor Falls' manages a similar feat with Bill. There was some question as to whether or not the Doctor's newest companion would be sticking around for the Chris Chibnall era, and it seems as though we have our answer. Moffat certainly sent Bill out with a bang, first blowing a hole through her chest, and then turning her into a full-on Cyberman. But it's to Pearl Mackie's credit, and the work she did during the season in making Bill as engaging a presence as she was, that the conclusion to her story was as emotionally fulfilling as it was. Bill being rescued by the Pilot from the season premiere was a nice touch, as Doctor pointed out how odd it was that a Cyberman was capable of crying. And though there was a touch of Moffat repeating himself, sending Bill and the Pilot out to explore the universe, just as Clara and Ashildr did at the end of last season, the emotional currency of Bill's romantic connection helps it play just differently enough.

With that Doctor Who says goodbye to another companion and sets the stage to say goodbye to both Peter Capaldi and Steven Moffat. It will be necessary to revisit 'The Doctor Falls' once the Christmas Special has aired and the new Doctor Who is presumably introduced on screen for the first time. There were a number of hints throughout the finale that the series was at last ready to cast a woman in the role of the Doctor. Hopefully that proves to be the case as the show is indeed ready for that kind of change and it would feel particularly fitting to introduce the first female Doctor along with Chibnall and presumably a new companion.

It's a little disappointing that we'll have to wait several months before this story reaches its conclusion, and David Bradley's appearance is fully explained. On the plus side, however, that kind of time will put a lot of distance between the audience and this finale, and it will be interesting to see whether or not this iteration of the Doctor is able to reconnect with his audience and asking them to say goodbye all over again.

Next: Peter Capaldi Returning to Comic-Con for His Final Doctor Who Panel

Doctor Who will return for the Christmas Special on December 25, 2017 on BBC and BBC America.