The Doctor is setting the TARDIS on course for one of the top planets in the universe, Appalapachia, but they travelers find themselves in a blank white chamber with a single door. The Doctor and Rory try to work out how to get through the door with two buttons, red and green, while Amy looks for her mobile phone. Rory finally pushes a button labeled “Green Anchor” and they find themselves in another plain white room with basic furniture. They go in and the door closes behind them.
Amy leaves the TARDIS and calls to them, and Rory tells her to push the button. She pushes the other button, “Red Waterfall,” and finds herself in an but identical white room with no sign of her friends. She steps in and the door closes behind her. Meanwhile, Rory looks out of his door and sees no sign of Amy. The Doctor pushes a green button on a magnifying glass-like device and brings up an image of Amy. Apparently she is in the same room, even though she can’t see them in the actual room and vice versa.
A white robot enters the Doctor and Rory’s room and welcomes them to the Two-Streams Facility, and asks if they’re staying long. The transmission device blanks out and the Doctor realizes that something has gone wrong with time. The robot advances on Rory, raising its hand, while the screen clears and Amy complains that she’s been waiting for a week. The Doctor realizes that time is moving faster in her room and manages to stabilize the image. He examines the hand-bot and realizes that it has human hands that it can use to “see,” even though it has no visual sensors.
Rory confirms that Amy pushed the red button, steps outside, and pushes the red button. However, there’s no sign of Amy in the room that he finds beyond the door. Rory returns to the Green Anchor room and the hand-bot explains that Appalapachia is under quarantine, and the building they are in is a Kindness Facility for those infected with Chin 7. The Doctor has heard of the disease, which kills within 24 hours. The hand-bot tells them to stay in the sterile areas and teleports out, and the Doctor explains to Rory and Amy that Chin 7 is only fatal to two-hearted species like the Appalapachians... and Time Lords. The facility compresses time in the red room, allowing those in the green to watch their loved ones live through the time glass for 24 hours.
The Doctor picks up the time glass, cutting off the signal, and moves around the room to confirm he can use it as a different location. He then informs Amy that he’s taking it back to the TARDIS so he can use it to get a lock on her and smash through into her time stream. When he moves the device, an alarm goes off. The Doctor tells Amy to go into the facility but to refuse any treatment because it could easily kill her. As Amy steps through the check-in door, she tells Rory that she loves him.
The Doctor and Rory return to the TARDIS and plug the time glass into the console. He then finds a pair of camera glasses and puts them on Rory, explaining that he’ll have to go in since he’s immune to Chin 7. The Doctor warns that smashing through a time wall could be dangerous and activates the TARDIS.
Amy wanders through the facility until she activates a voice interface which shines a beam of light down on her. It says that it will be Amy’s guide and teacher. A hologram of a check-in girl appears at the desk and welcomes Amy, and invites her to check out the various entertainment zones. Amy goes to the departure gate and sees one of the hand-bots. It scans her with its hand and tells her that she’s carrying unregistered bacteria. When it tries to give her an antibiotic, Amy warns that she’s not from its world but it rejects her statement and advances on her. She runs and the hand-bot first tries to hit her with an injectable syringe, and then summon reinforcements. Amy leaps over the counter and runs into the lower levels as an unauthorized-resident alert sounds. More hand-bots teleport in, cutting her off, and Amy climbs into a heating outlet. They’re unable to detect her due to the fumes.
The TARDIS smashes through the time wall and appears in an art gallery. Rory goes out and sees no sign of Amy, and wonders if they reached the same room. The room is filled with pieces of art from across the universe and the Doctor explains that the Appalapachians are cultural scavengers.
Amy runs into a white room filled with a number of archways. She calls upon the interface and it explains that she can pass through the gates to the entertainment zones. Amy activates the garden archway and steps through to a vast alien topiary. She asks the interface where she can hide and then asks what the fumes were. The interface explains that the vents channel the exhaust fumes from the time engines that hold the timestreams in place, and provides their location. Two hand-bots teleport in and advance on Amy, and she slams their hands together, shorting them out. \Amy goes to the door where the time engines are located, writes a note on them telling the Doctor that she’s waiting, and goes inside.
Rory explores the facility and finds no sign of life. The Doctor has him use the sonic screwdriver on the time glass to try and get a lock on Amy. He discovers that there are 40,000 separate timestreams, each one belonging to a different patient. When Rory lowers the glass, a masked and armored figure attacks him with a sword. The figure hesitates and then says through a voice synthesizer that “she waited.” She opens her helm and reveals that she’s Amy. The Doctor realizes that the timestream lock went wobbley. Meanwhile, Future-Amy tells Rory to duck and then stabs and destroys a hand-bot coming up behind him. She alters its black box so that the cause of “death” shows as accidental rather than hostile, and explains that she’s stayed alive so long by making sure the facility doesn’t know she exists. When Rory wonders how she’s still there, Future-Amy tells him that he never saved her. Rory insists that he’s there to save her now but the Doctor messed up, and Future-Amy explains that she’s been there for 36 years, alone. She admits that she hated the Doctor and knows the Time Lord can hear him through the glasses. The Doctor tries to talk to her over the speakerphone by the Future-Amy says she has nothing to say to her.
Two more hand-bots advance on Future-Amy, who quickly disposes of them. As she goes off, Rory follows her and suggests to the Doctor that they go back and prevent everything from happening. The Doctor warns him that they locked onto the timestream and can’t alter it. Rory grabs Future-Amy and says that it doesn’t matter how old she is, but she says that the Amy he knew died long ago. The Doctor notices that she has a sonic screwdriver and Future-Amy says that she made it, and calls it a sonic probe.
Future-Amy goes to her makeshift quarters in the time engine chamber, which contains a handless hand-bot with a smiley-face painted on that she’s named “Rory.” She tells them that her life is hell and the Doctor vows to set things right. He asks to speak to the interface but Future-Amy informs him that it doesn’t work in the time engine chamber. She confirms that the garden is empty at this time of the day and goes there, telling Rory to stay with her or not.
As they go to the garden, Future-Amy explains that she’s reprogrammed the interface to tell her anything she wants. The Doctor asks the interface about a regulator valve for the time engines and learns where it is. He has Future-Amy put on the glasses and she and Rory share a brief chuckle at how ridiculous they look. She admits it’s the first time she’s laughed in 36 years. Rory steps away to leave her alone and the Doctor tells her that there’s still time to fix everything.
Rory walks through the garden and finds an archway. He approaches it from the side and bumps into an invisible wall. One of the hand-bots touches him, rendering him unconscious. It prepares to inject him with an antibiotic, but Future-Amy arrives in time to decapitate it. He wakes up and realizes that she’s been crying, but Future-Amy tells him not to push it. The Doctor tells them that he’s worked out a way to hijack the time engines and overlap Amy’s timestream at two points. However, Amy refuses to let him save her and then runs off as more hand-bots close in. As she goes into the time engine chamber, Rory notices faded handwriting on the doors and uses the time glass to read them. He tells the Doctor that Amy left them a sign and that she waited, just as the Doctor asked.
Rory goes after Future-Amy, who explains that the Doctor wants to rescue her past self from 36 years ago. However, they need her memories to do so. Rescuing so would eliminate her in the present, and she asks Rory and the Doctor to take her with them. The Doctor says that they can do it, but then “their” Amy will have to wait 36 years for rescue. Rory realizes that he has to choose and insists that Future-Amy existing is wrong. When he reminds her that he swore to protect her, Future-Amy walks away. Rory blames the Doctor, saying he should have checked the history books. When the Doctor says that’s not how he travels, Rory says he doesn’t want to travel with him and throws the glasses on the floor.
As the Doctor listens, he hears their Amy crying. He tells Rory, who uses the time glass to see her in the other timestream. He goes to Future-Amy and asks her if she honestly can refuse to help her past self. Future-Amy immediately tells him that she won’t help their Amy. Rory brings up the image of their Amy, who can see the time glass in her timestream. Future-Amy approaches the time glass and remembers seeing the events from her past. She tells Amy that she won’t let the Doctor and Rory destroy her, and tells Amy that she’ll do the same thing in her future. Amy asks about Rory and points out that Future-Amy named her hand-bot Rory. They remember Rory in high school and how he was the only boy for them, and realize that Rory is the most beautiful man they’ve ever met. Amy begs Future-Amy to eliminate herself for Rory’s sake. Future-Amy considers and then tells Rory that she’s going to pull time apart for him, steps forward, and kisses him.
Future-Amy leaves the time engine chamber with Rory in tow. She tells Rory to watch her back and demands that he take her into the TARDIS as well. He notes that would mean there are two of them, permanently, and Rory asks the Doctor if it’s possible. He admits he might be able to have the TARDIS sustain the paradox.
Using the time glass, Rory locates his Amy and the Doctor coordinates them, telling them to share a single powerful thought. He then tells Rory to reroute the regulator valve and get back to the TARDIS within ten minutes. While Rory changes the settings, the Doctor tells the Amys to start thinking. They both concentrate on the Macarena and when they shared their first kiss. Amy appears in her future and Rory runs to hug her. The two Amys share an awkward moment.
The spectacles short out and the Doctor warns them that they’ve created a massive power loss. Before the glasses are totally destroyed, he tells Rory that he has eight minutes left and he’s on his own. Rory tells the Amys that he’s never on his own with them. More hand-bots move in and Future-Amy gives Amy a weapon. They destroy the first waves of hand-bots but more of them teleport in. The trio goes around them and heads toward the gallery with the TARDIS. As they go, the two Amys argue about who will live where. They arrive in the gate room but realize they can’t jump within the same timestream. The hand-bots have locked the controls and enter through the gates.
Rory manages to unlock the gate to the gallery and the trio goes through. Future-Amy smashes aside the hand-bots so Amy and Rory can get to the TARDIS, but two more hand-bots intercept them. One of them renders Amy unconscious and Rory runs to her side. He picks her up and carries her into the TARDIS, while Future-Amy enters the gallery and sees them. As they enter the TARDIS, the Doctor confirms that Amy is fine and goes to the exterior doors. He sees Future-Amy running toward them, says he’s sorry, and closes the doors. Rory asks what he’s done, and the Doctor admits that he lied. There can never be two Amys in the TARDIS. Rory insists that they rescue Future-Amy, but the Doctor says it’s impossible and tells him to choose.
As Future-Amy pounds on the door, begging Rory to help her, she remembers the look on his face as he carried his Amy away and remembers being in the TARDIS with him. Rory starts to unlock the door and let her in, but Future-Amy tells him to stop if he loves her. She admits that if he opens the door, she’ll come in to save her life... and destroy her counterpart. Future-Amy tells Rory to tell his Amy that she’s giving her the days with Rory. Crying, Rory turns away from the door. Outside, Future-Amy turns toward a new wave of hand-bots, calls to the interface, and tells it to show her home. She talks about the boy she met there as the hand-bots render her unconscious.
As they wait for Amy to wake up, Rory asks the Doctor if he always knew he couldn’t save both Amys. The Doctor simply says that he promised to save Amy, and there she is. Amy wakes up and the Doctor leaves them alone. She asks where her counterpart is but no one answers her.