The BBC Media Centre have released an official synopsis for episode four of Series 8, titled Listen, which you can read below:
When ghosts of past and future crowd into their lives, the Doctor and Clara are thrown into an adventure that takes them to the very end of the universe.
What happens when the Doctor is alone? And what scares the grand old man of Time and Space? Listen!
Listen airs on Saturday 13th September on BBC One, with the broadcast time to be confirmed next week.