The Zygons last showed up in The Day of The Doctor, where they had their memories wiped by The 10th and 11th Doctors in order to broker peace with humanity. Kate Stewart of UNIT also had her memory wiped along with her assistant, Osgood, and under the threat of mutual annihilation they tried to negotiate peace with the Zygons.

zygon invasion 2The Zygon Invasion opens with Osgood, who’s last appearance was in the finale of Season 8 when Missy unceremoniously vaporized her. A fan favorite due in part to her wearing of iconic wardrobe items for various previous Doctors, her death was greatly mourned. But it’s clear early on that her story might not be done yet.  Osgood and her Zygon doppelganger recorded a message after the events The Day of The Doctor, explaining a plan put in place by UNIT to ensure the peace between Humans and Zygons. That plan was to allow twenty million Zygons to take human form and hide in plain sight, making the cease-fire holding both species in check so important. In retrospect, it might not have been the best plan.

Things went wrong, because before long Osgood is running away from a Zygon and desperately trying to contact The Doctor. He gets the message on board the TARDIS. The news isn’t good. Osgood has been taken hostage. The stalemate has been broken. When the Doctor calls Clara for help, however, she doesn’t answer her phone.

Kate Stewart returns to the show, and the show is better off for her being in it. She has been a great addition to Doctor Who, and a great way to bring UNIT back into the mix. We’ve already seen her previously this season, working with Clara, who seems to have become a contractor for UNIT. It’s strange that Clara isn’t with UNIT at the start of this episode, but as with everything on this show, there’s a good reason.

zygon invasion 3Clara arrives home to find a young boy alone on the stairs in her apartment complex. He’s lost his mother. After a bit of “Are you my mummy?” flashbacks the boy has been all but forgotten, although something is strange about the people Clara is encountering. She eventually finds her way to UNIT and The Doctor, and the whole gang is ready to search for Osgood and stop the Zygon invasion.

But there is dissension in the Zygon ranks. They claim humans violated the ceasefire and are holding Osgood hostage in order to claim the right to reveal themselves. We find out that Osgood and her Zygon counterpart were pretty much a mystery to UNIT. They never knew which one is which. Osgood was the first to know the Zygons were up to something and she (the one that wasn’t killed by Missy) ran off to investigate when she disappeared. Kate Stewart’s plan is to go in guns-a-blazing and storm the Zygon stronghold to save Osgood. The Doctor isn’t too keen on the plan but Kate has to do what she believes is best for Earth.

When the assault begins the Zygons attempt to deter UNIT’s attack by employing doppelgangers as a way to confuse the soldiers. One of the soldiers is asked to call in an air strike, but when she zooms in to see the target it is her husband and child. The Zygon doppelgangers are making it difficult to attack them by taking the form of the soldiers’ loved ones. It’s a brilliant plan. One that really makes the Zygons feel like a serious threat. How can anyone ever be completely sure there aren’t any Zygons left on Earth when the dust settles?

zygon invasion 4Clara continues to see people acting strangely, and when she sees two men dragging a “body-sized” bag into an elevator she can’t resist investigating. The elevator leads to a mysterious tunnel. Rather than poking around any further Clara has a moment of clarity and returns to UNIT HQ to use the resources at her disposal. It looks like people have been dragging suspiciously large bags into the elevator, and then disappearing, for months. The Zygons have apparently been kidnapping and replacing people for quite a while. It’s too late. Their plan is in full effect. Anyone could be a Zygon!

During UNIT’s assault on the Zygon stronghold one of the soldiers encounters his mother and is ordered to kill her, as well as other innocents. He, along with his squad, can’t resist the lure and walk right up to their execution. It’s a great moment when you’re not quite sure if the soldier will fire on his own mother. The tension is palpable. If he had fired it would have been a really interesting choice for the show. I almost interpret the solider’s actions as him choosing suicide rather than risk killing his mother for the sake of humanity. I can’t say that was the intention, but I can’t shake the thought.

The Doctor finally finds Osgood, but by now the audience can’t possibly take any encounter with anyone at face value. Pun intended. The omnipresent threat of not knowing who is “real” puts me on guard for what we see the rest of the season. Are we going to get the same ruse pulled on us as when Amy and her baby were Flesh Avatars? I sincerely hope not.

zygon invasion 5Osgood becomes a rather interesting character when she’s asked by the Doctor to identify her true identity. She refuses to tell him, stating that her part in the truce is almost sacred to her. Her “sister’s” death doesn’t break her from her promise to uphold the truce at all costs. The Doctor respects her for taking that position, and I think it makes her a much more interesting character than she was before. She’s no longer just the Doctor Fangirl who works for UNIT. She represents a moral standard few live up to in Doctor Who. Only The Doctor’s companions ever live up to that ethical code.

Speaking of companions, things get really interesting when Clara brings a squad of UNIT soldiers to explore the tunnel she found. They stumble on dozens of human doppelgangers in stasis in the tunnel. Except that they aren’t doppelgangers; the stasis pods are actually filled with the real people… Including Clara! It’s a scary moment. One that I’m embarrassed to say I didn’t expect.

The mind instantly wanders to thoughts of Zygon-Clara’s next meeting with The Doctor. It also makes me worry that we will indeed see a re-hash of the Flesh Avatar trick later this season. The next episode is the second half of this two-part story and it would be a mistake to play the “whose who?” game beyond this point.

zygon invasion 6The episode ends with a cliffhanger as Zygon-Clara taking steps to kill The Doctor and Osgood. Kate Stewart has been compromised as well, and it looks like all hope is lost. The Zygon Invasion has begun.

Zygons are one of the most popular Doctor Who villains along side the Daleks, Cybermen, and Sontarans. But the Zygons have been in only a few stories, albeit very good ones, and the Day of The Doctor treated them more like a side plot than as the evil monsters they are. The Zygon Invasion is the episode that brings the Zygons up to the level of the Daleks and Cybermen. Elements of Classic Who are all over this story, but with the dark dramatic tone Doctor Who has adopted over the last season and a half. It’s a fun ride through Doctor Who at its best, and I only expect great things next time, in The Zygon Inversion!