Separated from the Doctor, Clara discovers a new menace from another dimension.Flatline premieres Saturday 18th October at 8.25pm on BBC One.
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.
DOCTOR WHO - FLATLINE Promotional Gallery
Here's the latest collection of promotional images for this week's new Doctor Who episode - Flatline...