The BBC has released the official story details for the eighth episode of Doctor Who‘s new season.

Written by Peter Harness (‘Kill the Moon’), ‘The Zygon Inversion’ will air at 8pm on Saturday 7 November on BBC One.

The synopsis reads: “Shapeshifting Zygons are everywhere in the UK, and there is no way of knowing who to trust.

“With UNIT neutralised, only the Doctor stands in their way. But how do you stop a war? And what can the Doctor do to save his friends?”

The first part of the story, ‘The Zygon Invasion’, airs on Halloween.

Doctor Who executive producer Brian Minchin teased last month: “The UK has been taken over by shape-shifting Zygons, Clara is in a whole world of trouble… It’s a bit of an Invasion of the Bodysnatchers…”

Showrunner Steven Moffat added: “I think we have to be awfully careful here, but I would say within the terms of Doctor Who, which involves blobby monsters and action adventure, this is as close to addressing the modern world as we get. Now I’m not suggesting that it’s a political deconstruction of the way things are, but it’s a decent framework for discussing it in. Zygons live among us. What do we do about it? I think it’s good drama.”

Writer Peter Harness has also revealed that the story is “a partial sequel to ‘Mawdryn Undead'”, a story featuring the Fifth Doctor from 1983.

> Buy Season 9 on DVD on Amazon.

> Buy Season 9 on Blu-ray on Amazon.

Season 9 continues this Saturday on BBC One with ‘The Woman Who Lived’.

> Here’s everything we know about Season 9 so far.

Are you looking forward to ‘The Zygon Inversion’? Let us know below…