Those who have missed the Steven Moffat of Blink will be quite pleased by this episode. Clara Oswald continues to get the development she should have gotten a year ago and the RomCom elements are perfectly balanced against some well-directed existential horror.
One day The Doctor has a revelation - an idea of some form of life that, instead of evolving into the perfect predator or tracker, became the perfect hider. Beings that shadow all sentient life, giving birth to the feelings that one is being watched while alone and spawning the nightmare that something is under your bed that you can't see.
The Doctor goes to grab Clara to help him investigate this theory, as she is getting home from a disastrous first (and probably last) date with her co-worker Danny Pink. What follows is a snipe-hunt of intergalactic proportions. And by the time they're done, they will see the end of the universe and the start of something Clara had never imagined.
THE GOOD PARTS
* When Moffat is on, he is completely on and his script here is completely on. One can see the usual Moffat staples throughout (dating drama, the silly fears of young children made manifest, monsters that can't be attacked or even perceived directly, etc.) but the execution this time around makes it a bit less obvious than in Deep Breath or Into The Dalek.
* Much of the credit for that goes to director Douglas Mackinnon, who sells every moment of this episode visually. The pacing is played perfectly, with lots of long, lingering shots.
* A larger part of the credit goes to Jenna Coleman, who is finally starting to shine after being given material that allows her to display a personality beyond being Matt Smith's Impossible Girl. As in Robot of Sherwood, Clara is the one who winds up getting to the bottom of things while The Doctor is messing about. And we get not one but two scenes of Clara speaking to a scared child and helping them cope with their fears.
* We get more of the theme of soldiers and the idea of them being seen as killers instead of protectors. Clearly Moffat is building toward something with this season and - unlike Into The Dalek - the points here are made with a bit more subtlety.
* The last ten minutes, in which we learn more of The Doctor's background than I think may have ever been revealed in a single episode, are good and sure to spark discussion among Whovians. To Moffat's credit, the answers we are given only spark further questions. Was The Doctor adopted? What made him so sad at a young age? And how much has Clara influenced him and to what degree throughout his entire life?
* Though the episode does work well, one wishes Moffat would take some more chances with the material and move beyond his usual tropes. For instance, the monsters here are thematically too close to The Weeping Angels and The Silence.
* On that note, The Doctor is given surprisingly little to do in this episode after the remarkable opening sequence. And while Capaldi interprets the material through the prism of his Doctor, the script leaves him sounding a bit more like Matt Smith's Doctor whenever he interacts with other people.
* The jokes about The Doctor thinking Clara looks bad or that other people think she looks fat are beyond old at this point.
* Random Observation - NOBODY else notices the man in the space-suit wandering around in the background of the restaurant but Clara?
THE FINAL VERDICT
Steven Moffat indulges in his usual tricks but this time it works. This is due, in part, to some amazing direction, enough changes that this doesn't quite feel like Moffat's Greatest Hits Vol. 3 and a stellar performance by Jenna Coleman, who proves to be more than a pretty face when she's given decent material.