Synopsis:

When an underwater base comes under attack, the Doctor and Clara must save the frightened crew and defeat an impossible threat. But what is behind these terrifying events? And can they really be haunted by ghosts?

Cast: Peter Capaldi and Jenna Coleman.

Guest cast: Colin McFarlane, Sophie Stone, Zaqi Ismail, Morven Christie, Arsher Ali, Steven Robertson, Paul Kaye.

‘Doctor Who’ Series 9 airs Saturdays on BBC America at 9pm.