Parts: 1 (45-minute)
Writers: Steven Moffat
Airdate: 13 September 2014
Production Code: n/a

Doctor: twelfth
Companion: Clara

Story: After travelling on his own for some time, the Doctor has begun to develop a theory that every human being is being shadowed by a dangerous creature, constantly watching and listening, which has perfected the ability to never be seen. He hopes to be able to track it down by searching Clara's timeline for the night when she first had a dream that recurs throughout human history: a hand reaching out from under the bed to grab her ankle.

Clara, meanwhile, is embarking on a promising new relationship... or, at least, it would be promising if she didn't put her foot in her mouth so often. But when the Doctor shows up in her flat, asking for her help, Clara's promising new relationship takes a complex turn that she never anticipated...