Everyone agrees it shouldn't be possible for her to change her future, but the Doctor figures if anyone can do it, it's Amy. Because she's just that stubborn. (Sounds like something to keep in mind after Lake Silencio, yes?) However, there's a catch. Old Amy wants to leave with them. Both Amys would survive. The Doctor hems and haws and thinks that with some rigging, the TARDIS could sustain the paradox. With some double-sonic action and the time glass, he links the Amys. He tells them they need a signal, a "thought so powerful it can rip through time." He instructs Rory to fiddle with some wires in nearby a control panel. "Now, Amy, start thinking," the Doctor says, "the most important thought you've ever had." "Macarena," say the Amys. Not only was it the most important dance craze, but also the first time she kissed Rory. Rory throws some switches in the control panel and suddenly both the young and the old Amy are face to face. It's a little bit awkward.
It's also a little bit explodey. Rory's camera glasses short out and something begins smoking and popping on the TARDIS. "Rory, you're on your own," the Doctor says just before the glasses cut out completely.
Hand-bots beam in. Old Amy passes her younger self a wooden staff. They two of them quickly dispatch the hand-bots and make a run for it. As they're in mid-escape, the Amys start arguing about living arrangements and so forth. Old Amy figures she'll go traveling, but young Amy still doesn't seem too happy. They make their way to the gate room but can't get to the TARDIS in the art gallery. The gates have been locked from the outside. Old Amy gets to working on the console, flirting with Rory the whole time. He asks her to quit, but come on. She hasn't gotten any action in 36 years! Let her have her fun!
The gate to the gallery opens just as hand-bots beam in. Amy -- the awesome, older Amy -- goes charging at them, kicking and slicing and twirling and slicing some more. "Go! I've got your back!" she shouts. The young'uns rush into the gallery. A hand-bot anesthetizes Amy. She goes down. Rory whacks the hand-bot over the head with the Mona Lisa. The canvas tears. For some reason, this completely knocks the bot out of commission. When old Amy catches up, she's momentarily paralyzed by the sight of Rory tenderly carrying her younger self into the TARDIS. Old Amy runs for the TARDIS, but the Doctor shuts the door in her face. "I'm sorry," he says. It turns out he lied to her. The paradox of having two Amys on the TARDIS would be too much. Rory is distraught. "She'll die!" The Doctor argues that she won't ever have existed. But she's out there now, pounding on the door, begging to be let in. He tells Rory to choose which Amy he wants and puts his hand on the lock.