Opening up with an effective and creepy 'something clearly isn't right' scene that follows Clara as she watches the cliff-hanger ending of "The Zygon Invasion", "The Zygon Inversion" quickly explains how Osgood and The Doctor survived the plane crash before sending them straight into the belly of the beast, heading into London to confront Bonnie as she seeks out the Osgood Box in order to start the Zygon/Human war in earnest.
Moving quickly at first in order to get the set up out of the way before slowing down and culminating in nothing more than a conversation between a small group of people, the biggest strength of “The Zygon Inversion” is its sense of pacing, like “The Zygon Invasion” before it. Nothing about this episode feels either rushed or dragged out (a rarity in an episode of Doctor Who, frustratingly), and thanks to this the episode feels focused at all times, the stakes slowly climbing as the scope of the episode gets smaller, constantly drawing you in until the very end. It’s a small thing really, but an important one that allows all the other interesting things in “The Zygon Inversion” to work as they were intended.
And despite Doctor Who’s dodgy continuity and often ham-fisted approach to rewarding long-time viewers of the show, I actually really enjoyed the ways in which “The Zygon Inversion” tied back into “The Day of the Doctor”, particularly in the way that the finale of the episode develops and the reveal of what the Osgood box is and why it has to be that way. It seems to me that much of the potentially controversial politics of “The Zygon Invasion” have been dropped here in order to better explore what the Zygon/Human conflict means to The Doctor, and I can’t say that is a bad thing - the last 15 minutes of the episode are amongst the best of the season so far, completely captivating thanks to some great writing and a brilliant performance from Peter Capaldi, the kind of scene that reminds you how perfect Capaldi is for the role of The Doctor when given the right script.
Also given time to shine in “The Zygon Inversion” is Jenna Coleman, working overtime as both Clara and Bonnie. I’ve always thought that playing Clara must be something of a thankless role – she’s never been given the chance to develop in the same ways that other assistants such as Rose or Donna have and as such I don’t think that Coleman has ever really been given the opportunity to show off her acting prowess. Thankfully, Bonnie is a much more nuanced and interesting character than Clara has ever been, and scenes where Bonnie and Clara have to interact with each other (the middle part of the episode dedicated to that very idea) allow Coleman to show off what she can bring to the table when given the chance.
My only real complaint about “The Zygon Inversion” is that I find Osgood almost unbearable as a character, but that is down to my own personal opinions about the nature of fandoms and the ways in which certain shows encourage them rather than any fault of the episode itself. Overall, “The Zygon Inversion” is quintessential Doctor Who, a hugely entertaining episode that cements the “The Zygon Invasion”/”The Zygon Inversion” double-bill as potentially the best story of the season so far, at least drawing with the “Under the Lake”/”Before the Flood” double-bill earlier on. Despite my initial concerns, season nine of Doctor Who is quickly becoming my favourite season of Doctor Who since David Tennant left way back in 2010, and it's thanks to episodes like this one.
I just wish they'd drop the god-damn Sonic Sunglasses already.