The BBC have released a synopsis for episode eight of Series 9 and the concluding part of Peter Harness’ Zygon two-parter, The Zygon Inversion, which you can read below:
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 Zygon Inversion airs on Saturday 7th November on BBC One.