The BBC have revealed the synopsis for episode 4 of Series 9 - "Before the Flood" - which will air on BBC 1 on Saturday 10 October 2015 at a time yet to be confirmed:
On a remote Army outpost, a fearsome alien warlord - the Fisher King - sets in motion a twisted plan to ensure his own survival. The ripples will be felt around the universe. Is this chain of events inevitable? And can the Doctor do the unthinkable?
Writer: Toby WhithouseThe air time for episode 3 - "Under the Lake" - has been confirmed as 8.25pm on Saturday 3 October 2015.
Director: Daniel O’Hara
Producer: Derek Ritchie
Starring: Peter Capaldi and Jenna Coleman
Guest cast: Colin McFarlane, Sophie Stone, Zaqi Ismail, Morven Christie, Arsher Ali, Steven Robertson, Paul Kaye, Neil Fingleton, Peter Serafinowicz