The BBC has released the synopsis for the ninth episode of series 8, Flatline. The episode is written by Jamie Mathieson.
Separated from the Doctor, Clara discovers a new menace from another dimension.
But how do you hide when even the walls are no protection? With people to save and the Doctor trapped, Clara comes up against an enemy that exists beyond human perception.
Flatline airs Saturday 18th October on BBC One and 9/8 CST on BBC America.
[Source: Doctor Who TV]