'The Magician's Apprentice' brings back Peter Capaldi as The Doctor alongside his companion Clara (Jenna Coleman).
Doctor Who series 9: A spoiler-free preview of 'The Magician's Apprentice'
The guest cast features Michelle Gomez returning as Missy, together with Jemma Redgrave, Kelly Hunter, Clare Higgins and Jaye Griffiths.
'The Magician's Apprentice' will air this Saturday, September 19 at 7.40pm on BBC One.
"Where is the Doctor? When the skies of Earth are frozen by a mysterious alien force, Clara needs her friend," reads the BBC's description of the episode.
Doctor Who series 9: 10 exciting teasers for 'The Magician's Apprentice'
"But where is the Doctor, and what is he hiding from? As past deeds come back to haunt him, old enemies will come face-to-face, and for the Doctor and Clara, survival seems impossible."