The cliff-hanger The Doctor travels into the past to uncover the truth behind the ghosts while in the future Clara sees the phantom of the Doctor drift through the dark waters towards the underwater base... Does it work? Almost definitely. The Doctor's own death was teased in multiple classic Doctor Who cliff-hangers so it is only fitting that the show reintroduces this notion for series nine. And the image of a ghostly Twelfth Doctor, black chasms where his eyes should be, hovering in the black water is rather unsettling. At the other end of the scale, knowing the Doctor has died somehow in the past, you know time will be changed somehow. In this day and age, the Doctor isn't going to regenerate in episode four without anyone knowing. Overall Rating 7/10. A chilling cliff-hanger (and Peter Capaldi makes for a creepy ghost) only undone by the fact that you know the Doctor isn't really going to die...