“The Zygon Inversion” was full of suspense and moral reflection, the things we love about Doctor Who. In “The Zygon Invasion,” the presidential plane had been shot down, leaving us to wonder how the Doctor and Osgood would survive. Though we know the Doctor must survive, it was still shocking to see the visage of Clara firing a bazooka towards the plane. “The Zygon Inversion” picks up here, showing us not only these events on the ground, but how the real Clara, trapped in the Zygon pod, comes to understand what’s going on through the mental link she has with the Zygon Bonnie who has taken on her form.

Doctor Who is at its best when it successfully combines dramatic action and thoughtful dialogue. “The Zygon Inversion” had less of a heavy hand than “The Zygon Invasion.” Instead of providing a parallel to real-world political crises, “The Zygon Inversion” is more generically anti-war in the style of classic Doctor Who. Though there have been some impassioned pacifists amongst the Doctor’s incarnations in the old series, the Doctor’s pleas for peace have more emotional punch in new Doctor Who because of the guilt he has carried for his role in the conclusion of the Time War.

“The Zygon Inversion” included outstanding performances by Peter Capaldi and Jenna Coleman. Capaldi gave us a Twelfth Doctor who is not playing games. Instead, he is desperately trying to appeal to the best in humans and Zygons, through their representatives Kate and Bonnie, rather than fighting the worst in them. Capaldi played the Doctor with great directness and vulnerability, giving the second part of this story great emotional effect:

“I don’t understand? Are you kidding? Me? Of course I understand. You mean, you call this a war? This funny little thing? This is not a war! I fought in a bigger war than you will ever know. I did worse things than you could ever imagine. And when I close my eyes … I hear more screams than anyone could ever be able to count! And do you know what you do with all that pain? Shall I tell you where you put it? You hold it tight … till it burns your hand, and you say this … No one else will ever have to live like this! No one else will have to feel this pain! Not on my watch!”

Coleman’s portrayal of the Zygon leader Bonnie left no confusion about which character she was playing when she was on screen. You felt the determination and anger of this disaffected Zygon. In the final scenes where the Doctor tries to explain the futility of war, you can feel her struggle. It’s challenging to make a villainous character so complex that the audience can root against them while still being empathetic to their plight. The Doctor forgives Bonnie, but it’s Coleman’s portrayal that allows the audience to look beyond Bonnie’s actions by the end of the episode.

Writers Peter Harness and Steven Moffat deserve a lot of credit for the success of this episode as well. Some of the best writing is evident not only through the Doctor’s dialogue in the Black Archive, but in the scenes between the Doctor and Osgood. Despite the seriousness of events, Capaldi gets to deliver some great comedic lines such as, “You know I’m over 2,000 years old. I’m old enough to be your messiah.” The writers and director Daniel Nettheim created a story bounded on all sides by strong female characters. It didn’t feel as though everyone was waiting to be saved, but that the Doctor was working with equals who were taking action into their own hands.

Osgood (Ingrid Oliver) became a fully dimensional character, making us love her that much more. Turning down the Doctor’s offer to travel in the TARDIS because of the importance of keeping the peace on Earth reinforced Osgood’s strength as a character. After their plane is shot down by Bonnie, the Doctor talks nonsense to try distract Osgood, but she sees right through it, noting, “It’s one of your known character traits.” Osgood also immediately recognizes that the Doctor will be upset not knowing if Clara is alive or dead. The Doctor comes to realize that Clara is still alive only because Osgood understands that the text he receives is coming from Clara through the mental link Clara has with the Zygon. Throughout the episode the Doctor tries to get Osgood to tell him if she is human or Zygon, yet she refuses, realizing that the very point is that is shouldn’t matter.

“The Zygon Inversion” may have also been the best portrayal of Kate Stewart (Jemma Redgrave) we have seen yet. Her role was not overshadowed by her father’s past involvement with the Doctor, she independently overcame and manipulated the Zygons, and her compassionate “I’m sorry” to the Doctor showed us much more about who she is than any of her UNIT directives could have.

Clara was no companion, but the Doctor’s partner in “The Zygon Inversion.” It was through her own strength and awareness that she was able to both communicate with the Doctor and lead Bonnie down a path meant to end in helping the Zygon rethink her position. Clara had developed into someone who acts on the basis of her own assets and convictions without needing the Doctor to guide or save her. Not all companions become fully realized in this way, and Clara’s development is one of the strengths of the current season. Clara was not a threat to Bonnie because she is the Doctor’s companion, but because she is Clara.

Doctor Who is a science fiction show not just because it involves space travel, but because, as Issac Asimov once described the sci-fi genre, it’s grounded in science and what is possible. The best science fiction stories are those that explore difficult philosophical and sociological ideas, sometimes serving as moral allegory for the real world. “The Zygon Inversion” explored the concept of war and social conflict through the lens of the Doctor’s experience, creating powerful storytelling. The two boxes, each with Truth and Consequences buttons, were a powerful device to highlight the impact of war:

“This is a scale model of war. Every war ever fought, right there in front of you. Because it’s always the same. When you fire that first shot, no matter how right you feel, you have no idea who’s going to die! You don’t know whose children are going to scream and burn! How many hearts will be broken! How many lives shattered! How much blood will spill until everybody does what they were always going to have to do from the very beginning—sit down and talk! Listen to me. Listen, I just … I just want you to think. Do you know what thinking is? It’s a fancy word for changing your mind.”

In “The Zygon Inversion” Doctor Who gives us a thought-provoking episode that was strengthened with impressive performances throughout.