The Zygon Inversion - Synopsis

The BBC Media Centre have issued the synopsis for the eighth episode of the current series of Doctor Who:

THE ZYGON INVERSION - by Peter Harness & Steven Moffat
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?

Doctor Who: The Zygon Inversion will broadcast on Saturday 7th November at 8:00pm on BBC One and BBC One HD.