If I’ve not said it before (and yes, I have), this is the best season of Doctor Who in the post-2005 era. And the show has upped the ante with this week’s surprisingly realistic and gritty episode, “The Zygon Invasion.”

In Doctor Who‘s greatest era (that being the Hinchliffe/Holmes era of the mid-70s), the show was known for its homages to classic sci-fi/horror films and literature. In a sense, we have a revisiting of that philosophy in “The Zygon Invasion,” which is essentially Doctor Who‘s take on District 9, Alien Nation, as well as the obvious and perpetually Zygon-related comparison to Invasion of the Body Snatchers.

In this episode, we learn that a huge number of Zygons have been living amongst the human population of Earth ever since “The Day of the Doctor” (2013), voluntarily disguised (for the own safety) as humans. But a radical splinter group of them have grown sick of that arrangement and want to live in the open, no longer hiding their identity. One of the great things that Doctor Who occasionally does is give believable motivation to its monsters. How can you not disagree with this Zygon faction? Identity and expression are topics very much in the news these days, from Caitlin Jenner to gay marriage — people just want the freedom to be themselves. Is there a better way to try and gain that freedom than the methods that these Zygons have adopted? Almost definitely. But they’re displaced, angry and desperate, and that makes them dangerous.

Another thing that episode gets really right is the emotion attached to facing as an enemy someone who looks like your mother or your son. Even when you go into a situation knowing for certain that you’re facing a Zygon, but instead you find yourself leveling a gun at your mother, can you really act? Can you take the chance that it isn’t your mother? That was a great scene, and we all knew exactly how it would end, and had this been anything other than Who, you could easily imagine it ending with the soldier not taking the chance and gunning the perp down, only to then learn that it actually was his mother. But the fear and the doubt that the characters in the show display is incredibly real and very believable.

On top of all that, we get the return of Osgood and Lethbridge-Stewart, we get lovely references to the past (Osgood’s ? shirt lapels, the return of the Fourth Doctor’s scarf, the Seventh Doctor’s sweater, and a photo of the First Doctor), more rock ‘n’ roll Doctor, doppelganger Clara (an expected but nonetheless neat trick), extraordinary set design and lighting in the Zygons’ lair, and Kate being a bad ass, alone and in fashionable heels. We also get an incredibly strong performance by Peter Capaldi. Capaldi is bringing his all to this role and we’re getting one of the greatest Doctors in the history of the show.

Possibly more important than all of that, we’re getting a big, proper, scary, realistic Zygon story. I’m still waiting for a second big, proper, scary, realistic Ice Warriors story. And I’d still love to see a second big, proper, scary, realistic Sontarans story, but sadly I don’t think that’ll ever happen. Seeing the Zygons return as a special treat in the 50th Anniversary episode was quite exciting; seeing them brought back and treated with respect and developed further in a believable way makes my Whovian heart(s) happy.

As is always the case in Who, a lot depends on how the story is resolved in the second half, as especially in the modern era, Part Twos have ruined a potentially great story. I’m cautiously optimistic about this Part Two, though. I say ‘cautiously’ because I have extremely mixed feelings about Peter Harness‘s only other Who script, “Kill the Moon.” On the one hand, that episode demonstrates that Harness is a master at writing moral dilemmas and exploring all sides of an argument or problem, a trait that continues in “The Zygon Invasion” brilliantly. However, his science-y story resolution was atrocious. So as long as no Zygon pods hatch a moon or whatever, I think we’ll be fine.

Very much looking forward to Part Two next week!

If you enjoyed this review and would like to read more, order a copy of my book Doctor Who’s Greatest Hits: An Unauthorized Guide to the Best Stories From Time and Space!