The ninth series of Doctor Who continues tonight at 8:00pm on BBC One and BBC One HD, read on for the synopsis to the eighth episode:
THE ZYGON INVERSION - by Peter Harness
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 series continues next Saturday at 8:15pm with Sleep No More, more details coming then.