S01E04: 'Aliens of London'

The Doctor takes Rose home to visit family and friends but miscalculates the time and arrives a year later than planned. Mother Jackie and boyfriend Mickey reveal the anguish they experienced after their loved one's disappearance, with the Timelord receiving a meaty slap in return.

Away from the domestic strife, a spaceship crashes into the Thames, smashing into Big Ben along the way. This coincides with the Prime Minister's disappearance, with his role taken over by low level MP with a wind problem - Joseph Green. He is joined by the similarly fart-prone head of MI5 Margaret Blaine and transport minister Oliver Charles inside 10 Downing Street.

Meanwhile, lilitary chief General Asquith visits Albion hospital to examine a lone survivor from the crash. The Doctor follows swiftly behind and discovers the being is a genetically-engineered pig in a spacesuit. The frightened creature tries to escape but is shot dead by the military, much to the Timelord's disgust.

Harriet Jones - MP for Flydale North - is at 10 Downing Street seeking an audience with the acting Prime Minister, but accidentally stumbles upon Green, Blaine and Charles revealing their true hideous identity. She watches as they murder Asquith, before Charles quickly swaps skins with the deceased General.

The Doctor discovers that the spaceship is a subterfuge deployed by a greater force, and goes to Dowing Street with Rose to meet members of the United Nations Intelligence Taskforce (UNIT). As he awaits a meeting with the newly possessed General Asquith, Rose meets Harriet Jones and junior secretary Indra Ganesh and discovers the Prime Minister's body.

Blaine finds the inquisitive trio and reveals her true alien form, killing Ganesh. The Doctor and assembled experts are suddenly immobilized by an electrical charge on their IDs activated by Asquith, who reveals his true alien form and says he's a Slitheen. At the same time, a flatulent police officer pays Jackie Tyler a visit.