Doctors: Christopher Eccleston (Ninth Doctor)
David Tennant (Tenth Doctor)
Companions: Billie Piper (Rose Tyler)
John Barrowman (Jack Harkness)
Jo Stone-Fewings – Male Programmer
Jo Joyner – Lynda
Paterson Joseph – Rodrick
Nisha Nayar – Female Programmer
Noel Clarke – Mickey Smith
Camille Coduri – Jackie Tyler
Anne Robinson – Voice of Anne Droid
Nicholas Briggs – Dalek voices
Alan Ruscoe – Android
Jenna Russell – Floor Manager
Directed by Joe Ahearne
Written by Russell T Davies
Script editor Helen Raynor
Produced by Phil Collinson
Executive producer(s) Russell T Davies
Incidental music composer Murray Gold
Production code 1.13
Series Series 1
Length 2nd of 2-part story, 45 minutes
Originally broadcast 18 June 2005
The episode opens with the Daleks questioning Rose on what the Doctor will do next. The Doctor uses the extrapolator on the TARDIS to generate a protective shield around them as he materialises around Rose and a Dalek. Jack destroys the Dalek and they exit the TARDIS to speak to the Daleks. The Doctor is surprised to see the Dalek Emperor in command, and even more surprised when the Emperor describes himself as a god. The Emperor survived the Time War and escaped to Earth in a crippled ship, where he rebuilt the Dalek race by harvesting DNA material from selected humans that were transmatted to them by the Game Station. The Doctor observes that the Daleks have gained human traits and emotions from this process and have become deadlier than ever. The Doctor, Rose, and Jack use the TARDIS to return to the Game Station and prepare for an imminent attack.
Jack uses the extrapolator to shield the top six floors of the station and sets up defensive positions. The Doctor attempts to create a delta wave generator from the equipment on the Game Station. The delta wave will kill anything in its path, but needs time to charge up. The Doctor sends Rose into the TARDIS, and while she is inside he uses his sonic screwdriver to direct the TARDIS to return her to her home time. The Doctor appears to her via a holographic message and explains that he sent her home for her safety and to prevent the Daleks from getting the TARDIS. The Daleks begin to invade the Station, easily making it past the defences and killing everyone in their path. The Emperor contacts the Doctor and taunts him about the delta wave, revealing that he knows it will not only kill the Daleks but most of Earth as well. The Doctor tells him that humanity will survive in some form but that the Daleks cannot.
The TARDIS arrives back in London, and Mickey and Jackie are drawn to the noise of its engines. They rush to meet Rose, who is heartbroken at being sent away from the Doctor. Rose begins to notice the words "Bad Wolf" all around the area where the TARDIS has landed, and realises that it is a message rather than a warning. She enlists Mickey to help her try and open the Heart of the TARDIS, hoping the telepathic circuits will allow her to pilot the ship back to the Doctor. Rose tells Jackie that she met her late father Pete, and that she is the "young woman" who was with him when he died. Jackie decides to help by borrowing a large truck from a friend. With the truck pulling the panel on the console snaps open and Rose is bathed in the light of the TARDIS. The TARDIS doors slam on Mickey and Jackie as they try to enter, and it then dematerialises.
Back on the Game Station, the Daleks force their way to Floor 500, killing Jack and Lynda in the process. They file into the control room as the Doctor is about to fire the delta wave. The Emperor again taunts the Doctor, who cannot bring himself to kill so many innocent people just to destroy the Daleks. The Emperor declares the Doctor a coward and orders him to be exterminated, but before the Daleks can kill him, the TARDIS materialises. The TARDIS doors swing open and Rose appears, wrapped in the glow of the time vortex. She reveals that she is the Bad Wolf, and that she spreads the words throughout time and space as a message to lead her there. The Daleks attempt to exterminate Rose, but she easily stops them, disintegrating the Emperor and the entire fleet. The Doctor begs her to relinquish her new power, but instead she brings Jack back to life. As Rose begins to burn up from the power, the Doctor kisses her, taking the entire power of the vortex into his own body. He releases it back into the TARDIS and carries an unconscious Rose back inside. They leave in the TARDIS before a reanimated Jack can get back to them, trapping him on the Game Station.
Rose awakens on the TARDIS to find the Doctor in pain. He tells her that the act of absorbing the time vortex is destroying every cell in his body. Rose begins to panic as the Doctor tells her that he won't be seeing her again. After musing on what his next body will look like and telling Rose goodbye, he suddenly steps back and bursts with energy from the regeneration process as he begins to change. After a few seconds the energy dissipates, revealing the Tenth Doctor. The new Doctor briefly comments on his new teeth before offering to take Rose to the planet Barcelona.