In a laboratory, Dr. Kendrick informs his superior that the prototype has passed every test and is working perfectly. His boss, John Lumic, rolls out on a wheelchair and insists that the prototype is not simply a machine. Kendrick concedes but notes that the creature may still be in shock. Lumic is satisfied that his creation will never age, and he envies it. He asks the humanoid figure if it knows him, referring to it as his child, and it identifies him by name. Lumic insists that he is blessed, but Kendrick notes that the UN has to approve it as a new form of life. Lumic notes that they will refuse him, and has his creation kill Kendrick when he refuses to yield on the issue. He then informs his captain to set sail for Great Britain.
In the TARDIS, Rose and the Doctor are discussing a past adventure and Mickey listens as he holds down a button. The Doctor finally asks why he's holding the button, and points out that Mickey didn't have to hold it down for more than a few minutes. The console explodes and the TARDIS bursts into flames, and the Doctor realizes that the time vortex has disappeared. They crash and the Doctor realizes that the TARDIS is dead. He warns Rose and Mickey that they fell into nothingness and there's nothing outside to turn to for help. However, Mickey looks outside and tells them that they're in London. They go outside and find what appears to be everyday normal modern-day London in February. However, the Doctor points out the zeppelins overhead and warns that it's not their world. Mickey realizes that they're in a parallel world and Rose sees a poster of her dead father, Pete Tyler, successful and advertising soda in this world. The Doctor tries to remind her that Pete's dead to her, and this world's will have his own life, but she doesn't appear convinced.
Pete returns to his home, a luxurious manor, and is angrily greeted by his wife, Jackie. She has people setting up for her 40th birthday, but is unhappy that it says her actual age. Jackie complains that her biography say she's 39. She calls for Rose and demands to know why Pete hasn't bought her a zeppelin like everyone else. She points out that she has a diamond-studded ear-pod, a gift from Lumic, Rose finally comes downstairs: the family dog. Pete gets a call from Lumic, who tells him to tell Jackie to take care of the hand-made ear-pod. Lumic says he has work to do and won't be at the party, and the British President has promised him a decision. When Pete tries to pass because of the party, Lumic insists and then cuts off the connection, and then activates an ear-pod override on Jackie's unit. Jackie is upstairs checking herself. The ear-pod expands to create an antenna, and Lumic downloads the manor's security codes without her knowledge. He then calls his associate, Mr. Crane, and tells him to recruit additional staff.
The Doctor discovers that Rose has wandered off and angrily blames Mickey for not watching her. On the river, Rose notices Lumic's zeppelin pass overhead and hears her phone ring. She discovers that it's advertising a free trial period for broadcasts and watches a story about Lumic, who insists that he's in good health. In the interview, Lumic insists that his brain is more creative than ever.
In the TARDIS, the Doctor warns that the TARDIS can't run on the energies of a parallel universe, and that it's impossible to travel between universes now that the Time Lords and their devices are destroyed. Now they're trapped, but the Doctor notices a reflected spot of light. He realizes that they have power.
In the wastelands, Mr. Crane rounds up homeless people and invites them into the back of his semi for food. One of them, Jake Simmons, warns his friend Morris that people have been disappearing for months. Morris is too hungry to resist and runs into the truck with the others, while Jake films footage. The men inside scream and Crane's men seal the doors.
The Doctor confirms that one power cell is clinging to life, and he supplies some of his own energy to cause it to start regenerating.
Rose looks up Pete's address.
The power cell goes into a cycle, and the Doctor says it will take 24 hours to provide them with enough power to go home. He and Mickey find Rose and tell her what they've found, and the Doctor realizes that she's found Pete via the Cybus network. She's discovered that she was never born in this universe, and Pete and Jackie are married and have an expensive home and cars. Rose insists that she has to see Pete, but the Doctor warns that she can't be their daughter. Rose goes off and Mickey says he has business of his own. The Doctor hesitates and Mickey points out that he'll always choose Rose. Rose continues and the Doctor tells Mickey to be back in 24 hours and then goes after Rose.
Lumic arrives at the airfield and Pete is there to greet the President. He explains that Cybus Industries bought up his company, and the President notes that some people think that Lumic has bought his government as well. As they wait, the President asks Pete for his opinion of Lumic, and then wonders if Lumic is insane. Pete insists he isn't, but the President doesn't appear convinced. He then goes aboard the airship
Mickey wanders the streets and comes to a Cybus Industries checkpoint. They warn him that the curfew is at 10 and let him into the poorer part of London. Elsewhere, Rose explains that Mickey's grandmother is dead five years ago from an accident and his father left. The Doctor figures that Mickey is looking for this universe's version of his mother. Everyone on the streets freezes and the Doctor realizes that the ear-pods are responsible and they're receiving news downloads. Rose's phone rings and the Doctor realizes that Cybus is responsible. Everyone suddenly laughs at the same downloaded joke and moves on. The Doctor checks Cybus' ownership and realize that Pete works for them, and he finally gives in and agrees to go to the party.
Mickey goes to his grandmother Rita-Anne's home and finds her, blind. She recognizes his voice but calls him Ricky. He gives in and she demands to know why he hasn't called, and that people have been disappearing. Mickey notices the loose carpet on the stairs and apologizes for never fixing it. She invites him in for a cup of tea, and admits she doesn't trust his new friends. As they talk, a van pulls up, Jake leaps out, grabs Mickey, and hauls him away. As they drive away, Jake calls Mickey "Ricky" and reminds him that he said they should avoid their families to avoid drawing the authorities to them. The third member of the group, Mrs. Moore, says that the vans they've been following belong to a Cybus dummy corporation. Mickey is the number one on the list as "most wanted" now that the rest of their group has been arrested.
Lumic gives a presentation demonstrating how the human brain can be preserved and placed in a metallic body. The President refuses to approve the process and warns that no government ever will. When Lumic reminds him that he's dying and need the process, the President expresses his condolences but remains firm. He tells Pete that he'll see him at the party that night and leaves. Lumic dismisses Pete and then contacts Crane, who tells him that the override worked and everything is in place. Crane examines the homeless men, who are all immobile and equipped with earpieces. He uses a remote to give them orders and they mindlessly obey. Lumic tells him to begin the upgrade. Crane sends the men off to another laboratory where screams echo out of the chamber.
Jake, Mickey, and Mrs. Moore return to their base and discover that someone is waiting for them: the Mickey of this universe, Ricky.
The Doctor and Rose approach the Tyler manor and sneak in as serving staff. They spot the President and others in the crowd. Pete calls for everyone's attention and introduces Jackie, who tells everyone to enjoy the party. They walk past Rose, and the Doctor warns her again that she can't stay. Rose admits that she has her mother, but in this world, Pete and Jackie have each other. When Jackie calls for Rose, Rose reacts until she discovers that Rose is the dog. The Doctor can't help laughing.
Crane checks the delivery floor as metallic figures march into trucks. He tells the drivers to start up and confirms with Lumic that they're departing. Lumic says that he's arriving and orders him to prepare the factory and begin the good work.
At the rebel headquarters, Jake scans Mickey and confirms that he's human. They suspect a Cybus trick and wonder if Mickey is a clone. Ricky explains that they have refused to use ear-pods and make themselves subservient to Lumic, and they plan to bring him down. They get a transmission from their inside man, who informs them that Lumic is making his move. Ricky orders his people, the Preachers, to pack up and leave. They follow the semis and arm themselves,
The Doctor slips away and notices an active computer screen in a darkened room. He checks it out, smiling. Meanwhile, Rose is watching Jackie with the President when Pete comes up to get some champagne. She compliments him on the party and asks about their marriage, and if they ever had kids. Pete admits that they kept putting it off and it's too late because he moved out last month. They plan to keep the divorce quiet, and Pete wonders why he's telling it to Rose. He thinks she seems familiar and says that she feels "right," and then walks off to discuss Torchwood with another guest.
The Preachers confirm that the semis are going to the Tyler manor, The metallic figures march out of the back of the trailer and the Preachers hastily go after them.
The Doctor taps into the computer and listens to Lumic's presentation.
Rose finds Jackie sitting outside by herself and asks if she can do anything for her. However, when Rose suggests she give Pete another chance, Jackie takes offense and storms off. Suddenly lights springs up on the yard and Rose sees the metallic figures marching toward the manor.
The Doctor sees the presentation on cybernetics, and sees a familiar shape take place. He realizes what it means and runs to find Rose. They watch at the window as the figures approach the house, and the Doctor warns that he's seen them again. He informs Rose that they are Cybermen. The Cybermen burst into the house and corner the guests, Lumic addresses them over the transmitter and refer to them as Cybermen. The Doctor explains that their human brains in robot bodies, their emotions stripped. Lumic boasts that they are homeless people but he has given them immortality. As Lumic sounds off, the Cybermen inform the President that they are Human 2.0 and that everyone will receive a full upgrade. The President objects and the Cybermen tell him that upgrading is compulsory. When the President asks what happens if he refuses, he is informed that he is incompatible and then "deleted": electrocuted and killed. The guests panic and the Doctor and Rose run for it, while Pete and Jackie are separated. The Cybermen continue deleting guests, while the Doctor gets Rose outside. However, they find more Cybermen closing in and are forced to retreat back to the house. Pete jumps out and joins them when he sees there's no escape.
Jackie takes refuge in the cellar but a Cyberman pursues her.
The Doctor, Pete, and Rose find every means of escape cut off. Ricky and Jake arrive and open fire, but their bullets have no effects. Rose embraces Ricky, who has no idea who she is. Mickey arrives and the Cybermen surround them. The Doctor tells Jake to surrender because their weapons are useless. However, the Cybermen insists that they are incompatible and will undergo maximum deletion.