In New York City in 1938, Julius Grayle hires Detective Sam Garner to investigate a case of statues... statues that move when no one is looking. Garner is glad to take his money, gets an address from Grayle, and leaves. Once the detective is gone, Grail nervously looks outside at the decorative statues around his house.
Garner goes to the address in Battery Park where Grayle claimed the statues lived. As the detective approaches the hotel, Winter Quay, he notices local residents all looking outside their windows. One girl covers her eyes and opens them repeatedly. Garner walks past an angel statue and enters the building, and an elevator descends, empty. Garner gets in and the elevator goes up as the lights flicker ominously. The PI walks down the hallway to a room belonging to a S. Garner. He goes inside and calls to anyone inside but gets no answer. There's a wallet on the bureau with his detective's license in it, that matches the one he has except older. Garner hears someone moving in the next room and goes to investigate. An old man is lying on the bed and he warns Garner that "they" are coming to send him back in time. Garner investigates and discovers that the old man is him, only decades older.
Garner runs out into the hallway only to find a stone angel blocking his path. The elevator doors open, revealing another Angel. When he looks back at the first one, he discovers that it has moved closer. Every time Garner looks at one, the other one moves closer. He runs into the stairway only to discover more Angels on the stairs. He runs up to the roof as the building shakes.
Somewhere, someone writes the story of a dying man.
Garner turns and sees the Statue of Liberty, its fangs bared, standing just behind the building.
In modern-day New York City, the Doctor, Rory, and Amy are taking in Central Park. The Doctor is reading a detective novel out loud, much to Amy's annoyance. The story is about a female detective, Melody Malone, with a heart of gold. He points out that there's something different about Amy but she ignores him. He finally realizes that she's wearing reading glasses and complains that they make her eyes look liney. Rory goes to get coffee but Amy asks him if the Doctor is right. He insists that she doesn't look liney and tries to avoid the topic entirely. They kiss and the Doctor looks on in disgust, and Rory goes to get coffee. Amy asks him to read and the Doctor rips out the last page of a book. He explains that he hates endings and then starts reading.
Rory gets their coffee and walks back past a statue of cherubs. He hears giggling sounds but looks back and doesn't see any children. He keeps on going but hears the same noise again as he walks through a building. Something flutters near the ceiling and Rory looks around nervously.
The Doctor continues reading and realizes that the last few lines are what Rory said and did, ending with him saying, "Hello, River."
River greets Rory, who is suddenly on a NYC city street in 1930s at night. She suggests that he put his hands up as Grayle's men arrive and capture them both.
The Doctor admits that he doesn't know what's going on as they go back to the TARDIS and sets a course based on the date in the book. As he sets a course, he tells Amy that the book just appeared in his jacket and he doesn't know how it got there.
As their captors drive them away, River concludes that Rory couldn't have come there in the TARDIS.
The Doctor and Amy, reading, wonder why the TARDIS couldn't have brought Rory there.
River explains that New York City is filled with time distortions and the TARDIS couldn't have landed there.
The TARDIS arrives in 1938 and hits a time distortion, bouncing off.
When Rory wonders how River got there, she explains that she used a time manipulator, which is much more maneuverable.
The TARDIS materializes in a cemetery back in 2012 and the Doctor realizes that the Angels have sent Rory back in time. He believes that the cemetery is somehow linked to 1938. Amy continues reading the book and says that the Doctor breaks something because she had no choice. The Doctor stops her from reading, warning that she can't read ahead about their own future. Once she reads it, it is set in place and can't be changed. Now he will break something because Amy read that he's going to do it. They go back in the TARDIS, unaware that one of the tombstones has Rory's name on it.
Grayle's men bring Rory and River to their employer's manor. Grayle is impressed with her knowledge of his collection of artifacts, including a Chinese vase from 221 B.C.
The Doctor tries to rig the TARDIS to bypass the time distortions. He needs something to lock onto and has Amy describe the Chinese vase in the book.
River realizes that Grayle is frightened while Rory reads the writing on the vase and realizes that the TARDIS is translating to him. Grayle tells his hood to give Rory to the babies and the hood tosses him into the basement. He tells Rory that the lights are out and tosses him a book of matches. When Rory wonders why he cares, the hood tells him that it's funnier if he uses them and locks Rory in as something giggles in the darkness.
The TARDIS materializes in 221 B.C. China and the Doctor identifies himself as an inspector for the Emperor.
As River goes to Grayle's office, she notices a Chinese vase with "Yowzah" written on it. She realizes that Grayle is a crime lord with a collection and notices a set of drapes. She yanks them opens, revealing an Angel with a scarred face, chained in place. She then sends a message on her time manipulator.
In the TARDIS, the Doctor picks up River's signal and locks onto it.
Grayle explains that the Angels move when no one is looking and that there are hundreds of them across the city. River assures him that she knows about the Angels and Grayle knows that she only investigates cases involving the Angels. The crime lord explains that he tortured the Angel to see if it feels pain, and River warns him that the other Angels can hear it screaming. As she nears it, Grayle turns off the lights for a moment. The Angel grabs River's wrist and then freezes, and Grayle orders him to tell her everything she knows about the Angels. He then turns off the lights again.
Rory lights a match and looks around the basement. More giggling noises echo and Rory sees a pile of stone cherubs. His match burns out and something runs in the darkness. When Rory lights another match, he discovers that the cherubs are now standing and moving toward him, frozen at the moment when he lit the match. He tries to light another match off the first one but fails, and by the time he lights a new one, another cherub has moved next to him and blows out the match.
River tells Grayle that the Angels are predators. The crime lord says that he's a collector and couldn't resist, and River warns him that's what the Angels anticipated. The building suddenly shakes and the lights flicker as the TARDIS materializes in the antechamber. River realizes that the Doctor is burning out the energy and warns Grayle that her husband is coming. The backlash knocks Grayle out. Amy heads for the door but the Doctor tells her to wait while he checks his looks. They finally go out and Amy calls to Rory without response.
The Doctor makes sure that Grayle is okay and then asks River where they are. She tells him that she was pardoned because the person she killed never existed according to the records. The Doctor scans the Angel and confirms that it's too weak to send River back in time. She jokingly asks if the Doctor is going to break her wrist or the Angel's to free her, and then realizes that the Doctor is going to break her wrist. When River asks why, the Doctor says that he read it in a book. As Amy comes back, the Doctor says that he has no choice. He shows River the book and explains, and she agrees that it's too dangerous to read ahead. Amy suggests they read the chapter titles and he turns to the table of contents. Among the chapters are "The Roman in the Cellar" and "Death at Winter Quay," and the Doctor realizes that Rory is in the cellar. Amy takes the sonic screwdriver and runs off. The Doctor starts to go off but then hesitates and River wonders what's wrong. He looks at the table of contents in horror... and the last chapter, which reads "Amelia's Last Farewell." The Doctor starts to panic and then tells her to get her wrist out without breaking it and change the future.
In the cellar, Amy calls to Rory. The Doctor catches up to her and they spot a pile of burnt messages. As the baby Angels giggle, the Doctor tells Amy that they've taken Rory and they back up out of the cellar.
Rory finds himself standing in front of Winter Quay.
As the Doctor and Amy try to work out what to do next, River confirms that Rory has been moved in space but not in time. The Doctor stares at her in surprise, realizing that she got out apparently unharmed.
Rory goes into the lobby of Winter Quay.
The Doctor tries to work out how River got her wrist out without breaking it but she avoids the question while trying to work out where Rory is. She finally figures out that it's a few blocks away and the Doctor takes her hand and pulls her out. River gasps in pain and the Doctor realizes that she broke her wrist after all.
An empty elevator descends to the lobby and Rory hesitantly gets in.
The Doctor gives Amy River's time manipulator and instructs her on how to track Rory with it. He then asks River why she lied to him and she admits that she tried to do her best for the man she loves. The Doctor touches it and heals it with a little of his regenerative energy. She tries to stop him but he continues, restoring it. River slaps him, saying that he wasted his energy and that he embarrasses her by being sentimental. As River walks away, Amy tells the Doctor to stick to the science part and goes after her daughter. Outside, Amy asks River why she lied and River tells her that they can never let the Doctor see the damage and never let him see them age because he doesn't like endings.
The Doctor locates Rory at River Quay and they drive off in Quayle's car. Once they're gone, Grayle wakes up and discovers that the Angel in his study has disappeared. He glances at the front door and sees an Angel, frozen in place as it comes in. Grayle backs away in terror and finds another Angel behind him.
Rory gets out of the elevator and walks down the hallway. When he examines one room, the door opens on its own and he goes inside, unaware of the Angel down the hallway.
The Doctor, Amy, and Rory arrive at Winter Quay and River wonders why the Angels sent Rory there instead of back in time. They follow the tracking signal up into the elevator and find Rory in the room. The lights flicker and River and the Doctor find another Angel... smiling. The Doctor sees the name on the room, "R. Williams," and tells Amy and Rory to get out. It's too late, as they've seen an old man lying in a bed. He calls to Amy and she realizes that it's a dying Rory. The old Rory mutters Amy's name and dies. Rory asks for an explanation and the Doctor tells him that he just died.
The Doctor explains that Winter Quay belongs to the Angels. Every time some tries to escape, the Angels zap them back, generating the temporal displacement energy that they feed on. They hold onto their victims and feed on the energy over and over again, and they've created a battery farm. River confirms that the Angels have replaced every statue in New York City, which provides the ultimate food source. They hear something huge moving and the Doctor tells Rory that they're coming for him. Rory asks what is going to happen and the Doctor explains that they'll transport him back 30 or 40 years where he'll live out the rest of his life in the room. Then he'll die and they'll send him back again. The Angel was smiling because it was pleased to see Rory arrive again. When Rory suggests that he run, the Doctor says that he can't because they've already seen him die. River agrees with Rory, saying it would create a paradox that would poison the well and kill the Angels. The Doctor warns that it would be almost impossible and would take unimaginable power. Amy takes Rory's hand and says that she won't let him take them.
The enormous footsteps get louder and the Doctor warns Rory that even if they escape, the Angels would chase him for the rest of their lives. Amy opens the door and finds Angel waiting outside, and tells Rory to run. As they run, another Angel arrives and the lights flicker. As the Doctor and River try to leave, more Angels appear between light flashes.
Amy and Rory run down the stairs only to discover that the Angels have cut them off, forcing them to head for the roof.
The Doctor boosts the lights temporarily while he and River try to watch all of the surrounding Angels simultaneously. He finally tells River to run but when they get to the stairs they discover Angels blocking the way down.
Rory and Amy discover that the Statue of Liberty, an Angel, is standing outside the building. As Amy watches it, Rory goes to the edge of the building but realizes that there's no way down. However, he says that there's a way out and prepares to jump. Amy realizes what he's doing and turns around as Rory looks at the Statue of Liberty. She goes to him and he says that killing himself is the right thing to do. She begs him to come down but Rory says that if he generates a paradox then it will kill the Angels. Amy doesn't have an answer and Rory says that if the place never existed then he might somehow survive. He asks Amy to trust him and asks her to push him. She can't and says that Rory couldn't either if their positions were reversed, and he assures her he could do anything to save her.
Amy climbs up on the ledge with him and tells him to prove that he's right and they'll come back together. The Doctor and River arrive and Amy tells them that they're changing the future... and the couple jump. The paradox energies consume the building, there's a flash of light, and...
Amy and Rory wake up in the graveyard. The Doctor explains that they collapsed the timeline and the paradox worked, putting them back where they all belonged. He assures them that they got lucky and hugs them, telling himself not to do it again. The Doctor and River clean off the TARDIS and Amy and Rory come over to join them. However, Rory spots the tombstone with his name on it and calls Amy over. An Angel appears, touches Rory, and he disappears. The Doctor realizes that it's a survivor and tells Amy to keep her eyes on it.
The tombstone says that Rory died at the age of 82 and the Doctor tells Amy that he's sorry. One more paradox would rip New York City apart and both the Doctor and River say they can't go back. Amy walks toward the Angel, keeping her eyes on it, and says that there's room for one more name on the tombstone. The Doctor admits that he doesn't know if the Angel would send her back to the same time as Rory, but River says that it will work and tells the Doctor to shut up. Amy says that she believes it will work and that she'll be together with Rory as it was meant to be. River takes Amy's hand and Amy tells her to take care of the Doctor, while the Doctor warns her that she's creating a fixed point and he will never be able to see her again. He begs her to come into the TARDIS with him and she turns toward him. The Angel touches her and she disappears, and the tombstone now bears her name as well.
Later in the TARDIS, River dematerializes the vessel and the Doctor offers his condolences to her. She tells him that what matters is that he doesn't travel alone. He invites her to travel with him but she says that she can't travel with him all the time. River concludes that she has to write the book and send it to Amy to publish it, and promises to have Amy write an afterward for the Doctor in the hopes that he'll listen to Amy.
The Doctor goes back to get the last page that he ripped out. The afterward is from Amy, telling him that they lived well and were very happy, and will love the Doctor forever. She tells the Doctor that he should never be alone, and then asks him to go back to Young Amy and tell her the story of Amelia Pond to give her hope... and tell her that's how the story ends.