Doctor Who: The Timey-Wimiest Episodes Not By Steven Moffat
5. Under The Lake / Before The Flood (2015)
This two-part story features the Twelfth Doctor and Clara find a submerged installation that is plagued by ghosts.
As members of a local crew are killed, more deadly ghosts are created. The Doctor eventually travels back in time unravel the mystery of what has led to the events that he already saw in the future. But shortly after he leaves, his own ghost appears, apparently listing all the people who have died…with Clara next! This motivates the Doctor to work all the harder to solve the mystery.
In the end, it’s revealed that the Doctor’s ghost is an illusion the Doctor himself had created, with Clara’s name put next to spur his younger self to action.
To add to the timey-wimeyness, the second episode begins and ends with the Doctor talking to the camera about the “boostrap paradox”! (“Google it,” he tells us, in case we’re confused).