What if no-one is ever really alone?
Saturday, 13 September 2014 - Reported by Marcus
A new preview clip for this week's episode has been released by the BBC.
Listen debuts in the UK on BBC One at 7.30pm Saturday, followed by broadcasts around the world.
Listen: Preview - Doctor Who, via YouTube
Listen debuts in the UK on BBC One at 7.30pm Saturday, followed by broadcasts around the world.