The Doctor uses the TARDIS power cell to fire a burst of energy that disrupts the Cybermen and disintegrates one of them. Mrs. Morris arrives in the van and drives them away, while more Cybermen advance. Pete and Rose both want to go back to get Jackie, but the Doctor warns that anyone in the house is dead.
Jackie hides in the cellar as the Cybermen close in.
In the van, the Doctor warns that the power cell won't regenerate for another 12 hours. Ricky blames Pete and notes that he's been working for Lumic for several years. Pete explains that he's their mole within Cybus, Gemini, and confirms his story by providing the transmission signal. Ricky is forced to admit that he's Most Wanted for parking tickets, but insists he was fighting the power by parking wherever he wanted. Pete is unimpressed, but Rose assures him that she knew he wasn't a traitor. However, she can't explain why. Pete worries that Lumic will transform Jackie and the others. The Doctor shuts down the ear-pods in case Lumic is listening and explains that they have to notify the authorities that Lumic has assassinated the President.
Lumic addresses his Cybermen and asks what they think. They state that they all think the same, and want to upgrade humans to spare them pain. Satisfied, Lumic activates the ear-pod primary sequence and takes control of everyone in London. The people freeze where they're standing as he downloads new commands. IN the cellar, Jackie is also immobilized. She steps out and goes upstairs.
Panic spreads across London as the authorities realize the ear-pods are responsible.
Mr. Crane realizes what is going on and removes his ear-pod before Lumic can take control of him.
The fugitives spot the mind-controlled people marching, and the Doctor realizes what is going on. He warns that if the ear-pods are removed, it will cause a brainstorm. Pete explains that they're heading to Battersea where Lumic has a conversion centre. The Doctor explains that the Cybermen in "his" universe started on another world, while here they are originating on Earth. Ricky takes command and tells them to split up and meet at their headquarters. Mickey kisses Rose and then goes with Ricky. The others run and the Cybermen close in.
As they run, Ricky wonders what Mickey is, and admits that his friends aren't bad. The Cybermen close in on them and they split up.
The Doctor, Rose, Pete, and Mrs. Morris hide behind some trash bins. The Cybermen approach but the Doctor overrides their control signal with his sonic screwdriver and sends them away.
Controlled humans, including Jackie, arrive at the Battersea centre.
Ricky is trapped in a dead-end alley, and the Cybermen corner him before he can flee over the fence. Mickey is forced to watch as his counterpart is killed, and then turns and runs.
The Cybermen bring Crane to Lumic. Crane claims that his ear-pod malfuntioned and volunteers for an upgrade. However, it's a distraction so he can sabotage Lumic's controls. A Cyberman kills Crane before he can complete his work, and then suggests that Lumic upgrade. The millionnaire refuses until he draws his final breath, but they take control of his wheelchair and take him to conversion.
Jake and Mickey find the others, and Mickey informs them that Ricky is dead. Jake is digusted with him, insisting that it's nothing. The Doctor says they can mourn later, and they discover that the city has been sealed off. The Preachers have a schematic of the old factory, and the Doctor finds a way in from below. Pete suggests they go in through the front, and Mrs. Moore provides two sets of fake ear-pods. The Doctor warns that he can't show any emotion or he'll give himself away. Rose takes the second set and offers to go with Pete to find Jackie. He wonders why Jackie means so much to her, but Rose simply insists that the Doctor won't stop her. Finally, the Doctor finds the primary signal from Lumic's zeppelin and sends Jake to sabotage it. He then invites Mrs. Moore to come with him through the tunnels. Mickey offers to help and Jake reluctantly accepts his assistance. As they leave, the Doctor wishes Mickey luck and tells him to meet them at the TARDIS later.
The Doctor and Mrs. Moore climb down into the tunnels, which are chilled. They discover Cybermen, immobile and awaiting activation.
As Pete and Rose prepare to slip in, Rose explains that she's doing it for her mom and dad. They blend into the lines of controlled humans and enter the conversion centre.
Jake and Mickey climb to the roof and Jake prepares to kill the two mind-controlled human guards. Mickey insists that they don't kill them, and Jake provides some special "smelling salts" created by Mrs. Moore. The two men sneak up on the guards and knock them unconscious, and then board Lumic's airship.
As they make their way through the tunnels, Mrs. Moore explains that she used to work for Cybus Industries until she learned too much and they tried to call her. She admits that her name is made up to protect her family. She asks the Doctor about his family, but he says that he looks after the whole world. When he asks her real name, she admits she's called Angela Price and asks her to keep it a secret. They unwittingly set off a sensor, notifying the Cybermen. They activate the dormant units and the Doctor and Mrs. Moore flee past them to a hatch. They climb up just in time and the Doctor seals the hatch.
As they are led throught he conversion centre, Rose and Pete witness rejected human incinerated, while the chosen are surgically altered and transformed into Cybermen. One of the Cybermen recognizes Pete Tyler and explains that it was Jackie Tyler. When Pete and Rose react, the Cybermen take them captive. As they are lead off, Pete wonders if she can be cured. Rose warns that it isn't possible, and they soon lose track of her among the other identical Cybermen.
Jake and Mickey enter the Zeppelin control room and find a mock-up from Lumic's presentation. The two men go to work sabotaging the transmitter.
A Cyberman confronts the Doctor and Mrs. Moore, and Mrs. Moore throws an EMP bomb at it. The Doctor opens it up and examiens the interior, and finds its emotional inhibitor. He accidentally breaks it and the Cyberman says it was Sally Phelan. She underwent conversion on the night before her marriage, and doesn't want the groom to see her. The Doctor shuts her down for good and vows that Sally won't have died for nothing. He realizes that if he can feed the cancellation code for the emotoin inhibitor through every Cyberman's head, it will kill them.He's reluctant to slaughter them, but Mrs.Moore insists it has to be done. As she gets up, another Cyberman finds them and kills Mrs. Moore before she can fight back. More Cybermen arrive and take the Doctor away for analysis once they discover he has two hearts.
Mickey tries to hack the computer systems to get through the security door to the transmitter. He's unaware that he's set off a signal.
The Doctor is taken to Pete and Rose, who tell him that Jackie has been converted. He asks to see Lumic, and the Cybermen explain that Lumic has been designated Cyber-Cntroller. They open a door and reveal Lumic, converted into a new form of Cyberman seated upon a throne. It informs them that it is the creator of the Age of Steel.
As Mickey hacks the computers, the display Cyberman robot comes to life and advances on them. Mickey lures it into the transmitter panel where it smashes the device. Below, the humans return to normal and they run in terror. The Doctor hears the noise and realizes that Mickey and Jake have succeeded. Aboard the airship, the men tap into the camera system and listen as the Doctor points out that it is Lumic's mortality that drove his imagination, and that the Cybermen have no imagination. The Cyber-Controller wonders if he has suffered negative emtoions, and the Doctor admits that he has. However, he refuses to give them up and insists they make him what he is.
The Doctor says that everyday people are what make the world great, and starts talking about codes to override the emotion inhibitor. Mickey realizes the Doctor knows he's listening and starts typing as the Doctor and Pete feeds him the code. Once he has it, Mickey sends it to Rose's telephone, she tosses it to the Doctor, and the Doctor plugs it into the control console. The Cybermen go into convulsions and realize that they've been converted. They explode as the Doctor explains to the Cyber-Controller that he's given them back their souls, and it's killng them.
The Doctor, Rose, and Pete flee for the exit as the centre comes down around them. The door is blocked by convulsing Cybermen. Above them, Jake tries to depart in the zeppelin but Mickey refuses to leave the others behind. He tells the others to get to the roof. Behind them, the Cyber-Controller pulls free of his throne and screams in anger.
Mickey frealizes he can't lower the zeppelin any lower, but finds the rope ladder. He releases it and Rose, and then the Doctor and Peter, climb up. Halfway up, the Cyber-Controller grabs the rope ladder and starts climbing. The Doctor hands his sonic screwdriver to Pete and tells him to use it on the rope. Pete says that it's for Jackie and breaks the rope, and the Cyber-Controller plummets down into the exploding centre.
Later, the Doctor returns to the TARDIS and installs the regenerated power cell. Outside, Rose and Peter talk and he asks her about parallel universes. He asks who Rose really is and she hints that she's his daughter. Pete quickly starts to go, saying that he has to tell the authorities about the other conversion centres. When Rose calls him "Dad," he tells her not to and runs off. Mickey and Jake arrive and the Doctor tells Jake Mrs. Moore's real name, and tells him to find her husband and children and tell them how she died saving the world. The Doctor turns to go, and Mickey informs them that he's staying to replace his counterpart. He explains that Rita-Anne is still alive and she needs him, and that Rose doesn't need him when she has the Doctor. Rose says they'll come back, but the Doctor reminds her that travel between parallel worlds is impossible. When they leave, he'll have to close the crack. The Doctor gives Mickey the code to stop the Cyberman and wishes him luck. Mickey and Rose share one final embrace and then Rose leaves in the TARDIS.
Jackie is at home when the TARDIS returns to its own universe. Rose emerges and embraces her mother, who wonders where Mickey is. The Doctor tells her that Mickey has gone home.
Int he other universe, Mickey and Jake prepare to leave, and Mickey says they can remember Ricky by fighting in his name. He suggests they go to liberate France and assures Jake he once saved the universe in a big yellow truck.