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?
Writer: Peter Harness. Director: Daniel Nettheim. Producer: Peter Bennett.
Cast: Peter Capaldi and Jenna Coleman
Guest Cast: Ingrid Oliver, Jemma Redgrave, Nicholas Asbury, Aidan Cook, Tom Wilton, Jack Parker