SPOILERS BEHIND THE CUTS
Five years in the future, Amy Pond is married, settled down with Rory Williams and pregnant. Their quiet life is thrown into sharp relief when The Doctor comes for a visit.
Meanwhile, in the present, The TARDIS is dead in space and slowly drifting into a cold star - a star that radiates the coldness of the void as an ordinary star radiates heat. Here it is still the relative present for The Doctor, Amy and Rory and they are in very serious danger.
A switch in time and suddenly it is the future again. And a parasitic alien race that is hiding inside the bodies the village's elderly citizens emerges, intent on invasion and conquering the Earth.
A switch again and our heroes are back on an increasingly cold TARDIS.
A switch again and they are surrounded by zombie-like old people, who exhale an acidic mist through eyes in their mouths that kills within seconds.
A switch again and ice is forming on the TARDIS controls.
Which world is the fantasy? Which is reality?
Do you choose the mundane life with Rory or the life of adventure with The Doctor?
This is the choice that is leveled at Amy by The Dream Lord - an all-powerful being who is to the world of dreams what The Doctor is to Time, who has apparently set up this little test of wills - not only as a test of the character of our three heroes - but also to help Amy decide what is most important to her, as The Doctor and Rory both fight over which reality is the true one.
THE GOOD PARTS
* The Dream Lord is easily one of the best new villains to be created in the new Doctor Who series and a great callback to the classic cosmic villains of the original series, such as The Celestial Toymaker. The nature of his creation also seems to be a shoutout to The Valeyard - another villain whom many fans (including yours truly) have suggested may be appearing in the new series very soon.
* The mystery of which reality is the fake one is played off VERY well.
* Lots of good drama here as Amy's obvious attraction to both of her "boys" and what they have to offer her is explored.
* Rory finally comes into his own here, both in his actions to save an unconcious Amy and in - once again - telling off The Doctor. He's not quite as forceful as Mickey but he does prove himself to be capable in a crisis.
* The only real problem is The Dream Lord's motivation - if The Doctor dies, doesn't that mean he dies as well since he is a part of The Doctor? I suppose he could be the kind of crazy evil that doesn't care so long as the enemy is destroyed but still...
* Additionally, the hordes of old people shambling around on their walkers is more comical than sinister, which may well have been the intent.
THE DOCTOR'S DICK MOVE OF THE WEEK
The Doctor's assertion that he never abandons companions brought a chorus of "Yes You Do!" from everyone in my viewing group.
Seriously - just ask Sarah Jane Smith about The Doctor's ability to stay in touch after leaving the TARDIS.
The Final Verdict: Easily the best episode of Series 5 so far. A new villain. A story set in the classical mode of the early William Hartnell stories. And a Doctor who is horribly out of his element and dealing with forces even he can barely cope with for once. But - once again - the real treat and center of the action is Amy's inner struggle as she tries to decide what she really wants out of life. Almost a perfect episode.