The Rule: no unboxed spoilers until after this episode airs on the west coast of the USA (i.e., “Pacific Time” [sorry Alaska/Hawaii]. In other words, boxed spoilers until 3:00 AM UTC).
BBC synopsis: The Doctor discovers that the final days of humanity have arrived.
Radio Times blurb: Saturday’s episode of Doctor Who sees the world wake up to find the trees have moved back in overnight, leaving Clara (Jenna Coleman) and Danny (Samuel Anderson) trapped in London with their Year Eight Gifted and Talented Group.
Screenshot from last week’s “Next Time” trailer: http://i.imgur.com/eyNtZ4D.jpg (courtesy of Jragon). Google Maps Street View: Google Maps (you might have to zoom in to see why I’m putting this here )
Link to BBC One page with 3 trailers and an “introduction” to the episode that features comments by Capaldi and Moffat: BBC One - Doctor Who, Series 8, In the Forest of the Night - Clips. WATCH THE INTRODUCTION AT YOUR OWN RISK. It contains a significant spoiler for those who wish to go into the episode innocent of the plot.
Link to thread discussing the previous episode: Doctor Who (reboot) S08E09 -- Flatline (boxed spoilers until aired) - Cafe Society - Straight Dope Message Board.