The patients close in on the Doctor, Rose, and Jack. The Doctor commands them to go their room, telling them that he's cross with them. They turn around and go back to their beds. At the Lloyd house, Nancy watches as her brother, the Child, turns around and leaves.
Nancy watches as her brother walks down the street and then collapses, crying.
At Albion Hospital, the Doctor has Jack explain that how his con worked. Jack admits that he planned to lure in a Time Agent to buy the Chula spaceship, but then a German bomb would have destroyed it and Jack was free and clear. The Doctor notes that the Chula spaceship caused the Empty Child plague and goes upstairs with Rose, but Jack insists that he had nothing to do with it. The air raid sirens sound the all-clear but the Doctor warns that it's anything but.
As Nancy leaves, one of her children returns, wearing a real gas mask. Shocked, she realizes that he's unaffected. However, as she leaves, Mr. and Mrs. Lloyd grab her and take her back inside.
The Doctor goes to the ward where the first patient was taken and has Jack open the door with his blaster. They go inside and find a tape player and a shattered one-way mirror. There are children's toys and drawings scattered around the room and they realize that a child was the victim. The Doctor plays the tape, which has the Child asking for his mummy repeatedly, and recognizes it.
Mr. Lloyd threatens to turn Nancy in, but she blackmails him into helping her with food and tools by threatening to reveal he's the local butcher's lover.
The Doctor senses something and suggests that when the Chula ship landed, it infected one of Nancy's children. Now it has the power of the god. They hear the tape reel spinning and realize that the Child is still talking, and the Doctor realizes that he sent the Child to his room... the room they're in. Jack goes for his gun only to discover that the Doctor has taken it and replaced it with a banana. The Doctor blasts a hole in the wall and they escape into the hallway, and Jack takes the blaster and seals the hole. As the Child starts to burst through, they run but the other patients cut off their escape. Rose takes the blaster and puts a hole in the floor so they can drop to safety, and then seals the hole behind them. More patients come after them but they get out into an adjacent room and seal the door. However, they're trapped seven stories up. Jack suddenly disappears.
Nancy meets with her children, who thought she was dead. One of the children, Tim, writes a letter to his missing father with a typewriter and Nancy briefly snaps at him. She then tells him to continue, but warns the children that they need to consider what they'll do if she is killed. Nancy then shows them the wire-cutters she got from Mr. Lloyd and tells them she's going to the station where the capsule landed so she can find out how the Child died. When they worry that the Child will come after her, Nancy tells them that it's after her. She then points out that the typewriter is still typing even though Tim stopped. Nancy leaves and Ernie reads the paper, which has the words "Where is my mummy?" printed on it over and over.
Jack contacts the Doctor and Rose and explains that he used his one-man emergency teleporter to return to his ship. He tries to reprogram it and contacts them over the nearby radio using an om-com. The Doctor realizes that the Child is doing the same thing, and the Child interrupts to say that he's coming. Jack tries to block the signal using Glenn Miller music to buy them some time.
Nancy goes to the crash site and cuts through the wire barrier.
The Doctor tries to loosen the bars using his sonic screwdriver, and admits that he doesn't trust Jack. Rose insists that she trusts Jack and that he can "dance." The Doctor says that he can well, much to Rose's surprise. She turns up the radio and invites him to show her his moves, He takes her hands but then notices that they're undamaged despite the fact she hung from a barrage balloon rope. Jack teleports them to his ship, and the Doctor realizes it's a Chula ship. He snaps his fingers and summons the nanogenes, and explains they fix any physical flaws. He tells Jack to take them to the crash site, but Jack warns that they can't until he repairs the systems.
The soldiers capture Nancy as she enters the crash site.
As he works, Jack explains that the Time Agency stole two years of his memories, and he has no idea if he can be trusted. He completes the work and pilots the ship to the crash site.
Nancy put Nancy in a tent with a sick soldier, Jenkins. She notices that he has a scar on his hand and asks to be put elsewhere, but the commanding officer, Algy, refuses. As Algy goes, Jenkins says "mummy" and Nancy warns him that he's in the process of transforming. She begs him to release her before he infects her as well, but it's too late.
The Doctor, Rose, and Jack arrive at the crash site and Jack recognizes Algy from his squadron. Rose offers to distract the officer but Jack says that Algy is his type and goes to work. The Doctor, amused, explains that by the 51st century where Jack hails from, humanity has spread out across the stars and repopulated itself. Meanwhile, Jack approaches Algy, who calls him "mummy" and then transforms. Jack orders the other soldiers back and the Doctor realizes that the effects have become airborne. The sirens go off as the Germans launch another attack, and Rose remembers that Jack predicted a German bomb would fall on the site. The Doctor warns that it won't be in time and that soon the infection will spread across the planet. They hear singing and find Nancy in the tent. The Doctor frees her before the transformed Jenkins can revive.
Jack tries to open the Chula ambulance ship to prove his innocence, but he sets off an alarm. At Albion Hospital, the Child senses the alarm and it and all of the transformed patients head for the crash site. The Doctor gives Rose his sonic screwdriver and sends her with Nancy to seal the hole the girl made entering the site. As Rose works, she assures a skeptical Nancy that she's from a future London that scurvies the Blitz.
Jack opens the ship and reveals that it's empty, but the Doctor explains that it contained nanogenes, enough to build a species. The nanogenes found the dead Jamie and revived him, but now they believe that all humans should be rebuilt the same way, and they'll carry out their programming across the entire Earth. The patients approach the site and the Doctor explains that the ship is summoning the patients and has programmed them as soldiers, and equipped the Child with Chula weapons technology. The patients wait and they realize it's waiting for the Child to arrive. Nancy says that it's her fault and the Doctor realizes that Jamie is Nancy's son, not her sister
The bombs draw closer and Jack realizes what he has to do. He teleports to his ship and the Doctor explains that Nancy lied to everyone, including Jamie. Jamie burst through the gate and the Doctor tells Nancy that the Child won't stop until she tells him the truth about where his mummy is. She goes to the Child and tells him that she's his mummy. He keeps asking and the Doctor realizes that there's not enough left of him to understand. Nancy insists that she's his mother and embraces him, and the nanogenes surround them both. The Doctor understands what's happening and tells the nanogenes to work it out. The nanogenes recognize the same DNA and transform Jamie. The Doctor removes the boy's gas mask to reveal that he's fully restored.
The bomb plummets toward the site but Jack arrives at the last moment to catch it in his ship's tractor beam. Jack boards the bomb and warns that he can't hold it for long. He says goodbye to Rose and teleports back to the ship and then flies away. The Doctor then summons the nanogenes, reprograms them, and sends them to all of the infected. They're restored to normal and the Doctor exults that this once, everybody lives. He assures the restored Constantine that all of his patients will now be fully cured of all their ailments. The Doctor then sets the Chula ship to self-destruct and they return to the TARDIS. He insists that everything is fine, but Rose wonders why Jack said goodbye.
In space, Jack has his ship computer hold the bomb in stasis. However, they can only maintain stasis for three minutes and there's no way to get rid of the bomb or escape the ship. Jack initiates the emergency protocol to summon a glass of martini and enjoy one final drink. However, he turns and discovers the TARDIS has materialized onboard his ship. The Doctor and Rose are dancing around the TARDIS console as Jack comes in. Rose invites him to cut in but the Doctor remembers that he can dance.