The episode will last for 50 minutes, and finishes at 8.50pm. The Zygon Inversion, co-written by Peter Harness and Steven Moffat, will air on the same day on BBC America at 9/8C.
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?