While the TARDIS takes a very worried River off through the Vortex, the Doctor has some flashbacks to some various things and finally realizes what exploded, where the Cracks are coming from on the day of the wedding: The TARDIS, dead in the middle of a bright yellow sun, surrounded by stars, coming apart in his hands. Which still doesn't explain Rory, who was quite factually dead before he even got eaten by the Cracks. From his point of view, the Doctor asks again, here's what physically happened: He was in the cave, dying thanks to that old lizardy bitch, and then he woke up "a proper Roman, head full of Roman stuff." After a while, Leadworth and Amy and the Doctor just seemed like a dream, but then when he heard the other soldiers talking about the red-haired girl that was working with Fake Caesar and Exploding Cleopatra, it came back. They came back, he thought, for him.
"Oh, shut up. Go get her." (This is where the weekly groaning set in, but I'll try to spare you. The man sticks to his tropes, I'll give him that.) Rory's all existential about it, and why's he here, and she doesn't remember me, and the Doctor sort of radically recontextualizes everything into the typical nonsensical normalizing kitsch: Why's Rory here?
"Because you are. The universe is big. It's vast and complicated and ridiculous, and sometimes, very rarely, impossible things just happen, and we call them miracles, and that's the theory. 900 years, never seen one yet. But this would do me. Now get upstairs, she's Amy and she's surrounded by Romans. I'm not sure history can take it."
Sure, fine. The Doctor believes in miracles and looooove. Who cares about factual inquiry when you've got boys kissing girls and having no personalities between them. Here's an engagement ring so you can propose marriage to a woman who has literally never met you... Before she blows one of those soldiers. Hurry!
The TARDIS chills out long enough for River to step outside, and while she's gone that voice comes back -- Silence will fall -- and the console screen Cracks, and we realize we're at Amy's house in Leadworth, the night before the wedding. River notes burn patterns on the grass outside, and the door is off its hinges, and it's verrrry creepy. Upstairs, in Amy's room, she's moderately appalled by the intense fetishistic collections of dolls and dioramas and stories and fantasies and whatnot -- "Oh, Doctor, why do I let you out?" -- and then she notices other things in the pile: The Story Of Roman Britain, a storybook version of the myth of Pandora.