As The Doctor and Rose reminisce about a past adventure while the TARDIS is in-flight, Mickey begins to feel upset that the two take him for granted. However, before they can comment, the TARDIS is rocked by a huge explosion and goes dark. The Doctor determines that they have fallen out of the time vortex into the void, and have landed somewhere, but that the TARDIS appears dead. They find themselves on Earth in London, but in a parallel universe; zeppelins fly in the skies and Rose spots an advertisement featuring Pete Tyler as a successful business leader, even though her real father Pete had died in her universe. The Doctor notes that the TARDIS can only operate on power from its own universe, and spots a dim but glowing power cell in the bowels of the ship. The Doctor breathes into it, giving away 10 years of his life but allowing the cell to start to recharge, a process that will take about 24 hours after which they should be able to return to their universe. Given the wait, Rose is anxious to see Pete, even though she was never born in this universe, while Mickey goes to see if his grandmother, who had died in his universe, may still be alive. The Doctor, worried for both, ends up chasing after Rose.
The Doctor and Rose discover that most of the population of this universe wear special "EarPods", devices that when activated by a signal, download massive amounts of news and information directly to the wearer's brain, information that is also received by Rose's mobile phone. They learn that the EarPods as well as Pete's company is owned by the powerful John Lumic, owner of Cybus Industries, who is presently failing to gain approval from the Ethics Committee of Great Britain for his "ultimate upgrade": a method of sustaining the human brain indefinitely within a cradle of copyrighted chemicals and allowing its impulses to be bonded onto a metal exoskeleton. Lumic secretly has been capturing homeless people and putting them to work in his Battersea Power Station factory using the EarBuds as methods to control the homeless. Being rejected by the President of Great Britain, Lumic tells his right-hand man Mr Crane to begin the upgrade process; Crane drives an International Electromatics lorry and collects more homeless people, but instead of just fitting them with EarPods, they are subjected to a room filled with cutting and other machinery that transforms them into the new prototypes.
Mickey arrives at his grandmother's house to find her still alive, but before he can get acquainted with her, he is grabbed by people in an unmarked van and taken to a country house. One of his abductors, Jake, who call him "Ricky", tells him that he is the most wanted person in Great Britain, and that they have evidence of Lumic's dealing with the homeless people. When they arrive at the base, the real Ricky, Mickey's counterpart in this universe, is there, and explains he is the leader of the "Preachers" who reject the EarPods and have been tracking Lumic's actions. After clearing the confusion between the existence of Ricky and Mickey, the group learns of pending action by Lumic and, with Mickey in tow, make towards Pete Tyler's estate.
The Doctor and Rose arrive at Pete's estate and learn that there is a large party there that night, where the President of Great Britain and Lumic will be present. The Doctor and Rose pose as part of the serving staff to investigate, and learn that Pete and Jackie Tyler have a pet terrier called Rose. Rose meets both Pete and Jackie, Jackie telling Rose that Pete and her are no longer together. As the party gets underway, Lumic presents his plans for his prototype, which the Doctor recognizes right away. Before he can act, the partygoers hear the sound of troops surrounding the building, an army of metal men, which the Doctor tells Rose are Cybermen. As the Cybermen break through the windows, Lumic explains that they have been selected to be upgraded to "Human.2", and that every human will receive a compulsory free upgrade. The President resists, and a Cyberman tells him that if one does not wish to become compatible, they will be deleted, and electrocutes the President to death. As Jackie flees into the basement with a Cyberman in pursuit, the Doctor, Rose, and Pete jump out a window and find the Preachers there, firing their weapons at the Cybermen, though it is ineffective. As the episode closes in a cliffhanger, the Doctor, Rose, Pete, Mickey, Ricky, and Jake are surrounded by the Cybermen, who move in to make the humans perish under "maximum deletion".
Doctor David Tennant (Tenth Doctor)
Companions Billie Piper (Rose Tyler)
Noel Clarke (Mickey Smith)
Camille Coduri – Jackie Tyler
Shaun Dingwall – Pete Tyler
Roger Lloyd Pack – John Lumic
Andrew Hayden-Smith – Jake Simmonds
Don Warrington – The President
Colin Spaull – Mr Crane
Mona Hammond – Rita-Anne
Helen Griffin – Mrs Moore
Paul Antony-Barber – Dr Kendrick
Adam Shaw – Morris
Andrew Ufondo – Soldier
Duncan Duff – Newsreader
Paul Kasey – Cyber-Leader
Nicholas Briggs – Cybermen (Voice)
Writer Tom MacRae
Director Graeme Harper
Script editor Helen Raynor
Producer Phil Collinson
Executive producer(s) Russell T. Davies
Production code 2.5
Series Series 2
Length 1st of 2-part story, 45 minutes
Originally broadcast May 13, 2006