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The Doctor takes the Ponds to what he promises will be a stunningly beautiful planet but turns out to be a sort of hospital in a quarantined plague zone. The plague kills within a day so this place has set up an automated facility for visitors to watch their loved ones live out their entire lives in 24 hours. They do this by having multiple timestreams; the visitors sit in the regular stream and the ill live in a vastly accelerated one. Things go almost instantly awry and Amy winds up in the accelerated time stream. The Doctor can't go in after her because his species is susceptible to the plague. He warns her to avoid the facility's well-meaning robots, as the medicine they kindly dispense is deadly to humans.
Rory goes off to the rescue, but the Amy he finds has lived 36 years in her timestream. She's more than a little angry and blames the Doctor for abandoning her there. In her solitude, she's had to fend off the robots and eke out a meager existence in the facility's grungy basement. At first, she refuses to help Rory rescue the past version of herself, as it means the current version will cease to exist. She finally agrees on the condition that the Doctor rig up the TARDIS so that both versions can come along. She and Rory fight their way through the robots, but it turns out that not even the TARDIS can handle the paradox and only one Amy can survive. Rory has to decide whether to save his hot young wife or his bitter old wife. To his credit, it really tears him up. In the end, it's old Amy who makes the decision for him, sacrificing herself so that her younger self can live.
Want more? The full recap starts right below!The Doctor, Amy and Rory are headed to a planet called Appalappachia, which, as the Doctor notes, was voted one of the "Top Ten Greatest Destinations for the Discerning Intergalactic Traveler." He describes the planet's breathtaking scenery, which is in pretty stark contrast to the sterile white room into which the TARDIS has materialized. A pair of sliding doors awaits them. The Doctor wrings his hands and promises the paradise planet is just beyond those doors, so Amy heads back into the TARDIS for a plot device. In this case, it's her camera phone so she can take pictures of all this beautiful scenery. This gives the Doctor and Rory enough time to start off toward the doors on their own. Apropos of nothing, the Doctor's pants seem to be getting shorter. They're one hemming away from turning into Captain Kirk's capris. Anyway, there are two buttons on a panel. Rory pushes one labeled with a green anchor and the doors open into a white room. A large magnifying glass sits on a table in the middle of the room.
By the time Amy has retrieved the plot device, the doors have closed. "Push the button," Rory tells her. You'd think that he'd tell her which one to push, or that she would ask which one, but that would be silly! Stop being logical like that. Naturally, she pushes the button labeled with a red waterfall instead of the green anchor. She ends up in a room much like Rory and the Doctor's, except they're not in it. After a bit of fiddling about, they realize they can see each other through the big magnifying glass. A robot appears in the green anchor room. It is white, plastic and featureless except for its rubbery hands. "Welcome to the Two-Streams Facility," says a voice coming from the hand-bot's astomatous head. "Will you be visiting long?" it asks over and over. By the time the Doctor turns his attention back to the magnifying glass, Amy says she's been there a week. The Doctor rapid-fire blathers on about how there are two different timestreams and Amy's in a faster one. The hand-bot reaches toward Rory. Everyone screams because it's time for that crappy BBC America intro.
Back from the intro and the hand-bot is waving one of its hands in front of Rory's face. The Doctor explains that's how it sees. "Why not just give it eyes?" the Doctor wonders. Good question. No one answers. Everyone soon figures out how they ended up in different places, so Rory backs up and presses the red button. Amy's not there. The Doctor realizes they can't directly follow her into the different timestream. "Why is it never simple!" he cries. Well, duh, because then the episode would be over. The Doctor tries to explain that they're aliens and simply pressed the wrong button. You'd think an intergalactic destination such as Apalachicola would account for such things, but again, the episode would be over. So the hand-bot explains that the Appalachians are under quarantine. "This is a kindness facility for those infected with Chen-7," it explains. It's a terrible virus that compels its victims to host a TV show about jerks living in the same house. It's also a plague that kills within a day, the Doctor says, but only affects two-hearted races such as Time Lords and the Apple Chinchillas.