Parts: 1 (45-minute)
Writer: Steven Moffat
Airdate: 30 March 2013
Production Code: n/a

Doctor: eleventh
Companions: Clara

Creature Feature: the Great Intelligence
Special Guest: UNIT

Story: The Doctor, baffled by Clara's mystery and unable to track her down, has retreated to Cumbria in 1207, where he finds solace at a monastery, meditating and painting portraits of Clara from his memory. His isolation comes to an end when, unexpectedly, the TARDIS telephone begins to ring. On the other end of the line, to his shock, is Clara herself, having gotten the number from a woman in a shop, believing it to be a tech-support hotline.

Barely has the Doctor arrived at her front door when he discovers that London, and indeed the entire world, is under siege. Lurking deep within the internet is an alien presence, which manifests itself in the wi-fi signal, and is capable of targeting and uploading people who inadvertently give it access to their computers. Once their souls have been uploaded to its datacloud, leaving behind their lifeless bodies, the entity can feast to its heart's content. When Clara finds herself in its sights, the Doctor must race to save her from dying in his care yet again...