The universe died when the TARDIS exploded, Amy is dead, Rory is a plastic thing, the Doctor is stuck inside an inescapable prison box, and River was on the TARDIS when it went boom for some reason.
How was that not the final episode?
So, there’s a lot to digest here. For one thing, the Earth is still around in 1996 when Amy is just a little orphan girl living with her aunt. Stars are fictional. Amy really wants to go to the local museum where the Pandorica is located, and when she gets there and stays behind after hours, she manages to open it. And…the Doctor isn’t in there. Adult Amy is.
Yes, it seems that when the TARDIS exploded and took most of space and time with it, the alien races that locked up the Doctor all, well, died. There were a couple stone Daleks, and they sure seem dead. Rory is the only Auton still active, and he manages to get the Doctor out when a future Doctor appears to give his sonic screwdriver to Rory to open the Pandorica and then put Amy inside because somehow that will bring her back to life when someone eventually reopens it. Rory, as living plastic, will guard the giant box while the Doctor uses a vortex manipulator (the thing River uses to time travel) to go to the future.
Cut to 1996 where the Pandorica opens, reviving a Dalek, but bringing Amy, Rory, young Amy, and the Doctor together to save the universe, eventually including River because she was stuck in a time loop on the exploding TARDIS…which just so happened to be the sun in this timeline.
This all was a lot of fun. There were a lot of wheels spinning all over the place, but it never had the sort of frenetic pace that previous Doctors had. Sure, no one was exactly taking their time over the whole thing, but there were many nice moments like the Doctor angering Rory enough to get Rory to pop the Doctor one, a test to make sure Rory was still Rory (The trigger? Suggest Amy was expendable.). River gets through the whole adventure with a breezy spring in her step. And the Doctor, well, he wears a fez now because fezzes are cool.
It turns out there’s some light from the pre-TARDIS explosion inside the Pandorica, so simply putting the Pandorica inside the TARDIS will reboot the universe…without the Doctor. He’s on the other side, so he doesn’t exist to these people. Everyone else is fine. Amy even got her parents back because they were originally sucked into the crack. Just…no Doctor.
But see, if Amy can remember the Doctor, he can come back because…I guess that’s how memory works. And as she struggles with the memory of the Doctor from when she was small, thanks in part to a journal River sent her, she remembers and DEMANDS the Doctor come to her wedding in the middle of the reception, causing the TARDIS to appear, even getting Rory to wonder aloud how he could have forgotten the Doctor.
And then the Doctor’s there, and he even came appropriately dressed. Plus, this is a new showrunner, so the Doctor is welcome to attend the party. He even the ends the wedding by pointing out that there’s a murder on the Orient Express…in space.
So, you know, looks like Amy and Rory are gonna have a hell of a honeymoon.
Too bad there are still questions about why the TARDIS exploded in the first place…