"Listen" is the fourth episode of the eighth series of Doctor Who, and was first broadcast in September of 2014. It starred Peter Capaldi as the Twelfth Doctor, Jenna-Louise Coleman as companion Clara Oswald, and featured Samuel Anderson as Danny Pink. It was written by Steven Moffat, and contains many of the themes he has previously explored in Doctor Who.
First: a subjective review. I liked this episode, and was glued to my screen throughout. There is an entire cottage industry dedicated to dissecting and criticizing Doctor Who, and it is hard to watch an episode without paying more attention to the expected reactions than to the actual episode. And yet, every once in a while I can get in a groove and just be entertained, letting the magic of the show transport me, no matter how illogical or problematic the episode is after review.
That being said, what is this episode really about? Monsters under the bed and prickles on the back of the neck. Oh, and stable time loops and the nature of fear. The episode starts with the Doctor theorizing that we talk to ourselves when we are alone because we know that we really aren't: as nature has evolved perfect predation and perfect defense, it has also evolved perfect camouflage, or rather we can't prove that it hasn't. Trying to solve this mystery, The Doctor plucks Clara away from an awkward date with Danny, trying to find the moment when she had a nightmare about monsters under the bed. What starts as an obvious set-up manages to change direction two or three times, throwing out false leads and baiting-and-switching the viewer. At the end, it isn't clear exactly what happened. In fact, it isn't clear that anything happened at all that wasn't simply the Doctor engineering his own delusions into existence.
It could be that Moffat has gone over some of this ground too many times: perception, memory, time loops, identity and how they combine in a type of ineffable knot. That may be, but at least while watching this episode, I was a believer, at least temporarily.