The Zygon invasion has already begun, Clara fights for control, and “think” is just a fancy way of saying “change your mind.”
After the revealing to UNIT that Clara was captured and duplicated by Zygons, Doppelganger Clara, named Bonnie, intends to blow The Doctor’s plane out of the sky. However, with her mind waking up inside of her cell-like pod, Clara uses the mental link shared between Zygon and subject to manipulate Bonnie’s motor functions, causing her to misfire a rocket, and send The Doctor a message that she is alive.
Bonnie continues her plan to sow chaos on Earth and begins to force the remaining Zygons to turn into their true forms, spreading panic among the humans and bringing the reluctant Zygons to her side. But turning them one at a time isn’t enough to completely break the ceasefire and throw the world into war, and so she searches for the The Osgood Box.
Once she discovers the Box in UNIT’s Black Archive, where the ceasefire was originally brought to terms, The Doctor, Osgood, and Kate Stewart arrive on the scene. It becomes a battle of words between Kate and Bonnie, with The Doctor standing between them, trying to get them to think about their decisions before throwing the world into a war at the push of a button.
The theme of real world parallels continue in “The Zygon Inversion,” as The Doctor tries to stop a war from breaking out over fear and paranoia. Bonnie fears that there is no going back after the actions the Zygons have taken, and Kate fears what further atrocities the Zygons will continue.
The Doctor has had many moments when his words had an impact on his friends and enemies, and even the viewers. This moment though, the heartbreak behind them of what The Doctor has gone through, the Time War, and the events that took place in “The Day of the Doctor,” come to the forefront of this monologue.
Smith had a similar moment during “The Pandorica Opens,” which was, to me, the moment that I accepted him as the new Doctor. I think we just witnessed Capaldi’s own moment.
Doctor Who continues Saturdays on BBC.