The Doctor (David Tennant), Captain Jack Harkness (John Barrowman), and Martha Jones (Freema Agyeman) escape the dangers at the end of the universe using Jack’s Vortex Manipulator and return to present-day London. They learn that the Master (John Simm) has taken the persona of Harold Saxon, the new Prime Minister. He has created a phone network called Archangel, which subliminally influences the people to vote for him. Our heroes narrowly avoid a bomb set in Martha’s flat and discover that her family has been arrested. The Master gloats that the time-travellers are now wanted criminals.

Hiding out in an abandoned building, the Doctor uses Martha’s laptop and the TARDIS keys (who knew?) to create perception filters so they can move about without being identified. He tells the others about the Master’s past, including the fact that the Master as a child looked into the Time Vortex and was driven mad. A news report says that Saxon will be revealing Earth’s First Contact with an alien race called the Toclafane. UNIT moves the meeting to the flying aircraft carrier Valiant. Saxon boards the ship with his wife Lucy (Alexandra Moen). The Doctor, Martha, and Jack teleport aboard and discover that the Master has converted the TARDIS into a Paradox Machine that is building power to the moment of First Contact.

The trio enter the bridge of the Valiant just as the first Toclafane appear. The Master orders them to kill the US President (Colin Stinton). The Master reveals that he can see around the perception filters and uses his laser screwdriver to kill Jack, and he ages the Doctor a hundred years with Professor Lazarus’s Genetic Manipulator and the Doctor’s severed hand. Jack comes back to life and gives Martha his Vortex Manipulator so she can get off the Valiant.

The Master brings Martha’s family onto the bridge as the Paradox Machine activates. A huge rift opens up above the Valiant and six billion Toclafane emerge and kill a tenth of the Earth’s population. Martha turns to the aged Doctor and he whispers to her. She teleports away with the Vortex Manipulator, promising to come back. To be continued.

In a flashback to Gallifrey, the first black Time-Lord on TV appears. The Master as a boy wore a black-and-white outfit like that of the first Time-Lords on screen, but a later flashback shows them wearing the impressive robes and the huge collars designed by BBC staff designer James Acheson. The costume collection was on loan from the Doctor Who Exhibition in Blackpool. The Seal of Rassilon appears here for the first time since the Doctor Who TV movie in 1996. When the Doctor is aged, his makeup is reminiscent of the look of William Hartnell’s First Doctor. The Master was able to become Prime Minister because the Doctor brought down Harriet Jones. Fake websites and advertising were created for the Harold Saxon campaign, including an endorsement by Sharon Osborne.

The TV in Martha’s flat was made by Magpie Electronics from the Idiot’s Lantern episode. Not only does Martha have a crush on the Doctor, but Jack does too, and it appears so does the Master. As the Earth’s population is literally decimated, Mickey Smith’s voice is heard voicing the alarm. As the aliens invade, the music is Voodoo Child by the Rogue Traders from the Album Here Come the Drums. The Doctor Who theme is in a lower key than usual. The Master wears the 12th Doctor’s coat with the red lining. The Master offers a jelly baby to the President. John Simm said his role of Caligula was good practice for playing the Master.