Clara wanted another adventure, well it appears she's in for a real doozy.
"We are fighting an unknown homicidal force, underwater, in a nuclear reactor" the Doctor informs us in this clip. What's his plan to save the frightened crew of the Underwater Base? Are they really dealing with Ghosts or something else entirely?
The year is 2150 and apparently the crew was abandoned on the base. Is there a connection between the forces haunting them and the base itself? If these are indeed Ghosts, were they left there in the past to die as well?
Check out Doctor Who Season 9 Episode 3 to get to the bottom of things.