It's another ordinary day for London teenager Rose Tyler (Billie Piper), who spends a typical shift at her job at Henrik's department store. When an errand sends her to the basement, however, she discovers that the electrician, Wilson, is dead, and a collection of mannequins stored in an anteroom somehow comes alive and attacks her. She is rescued by a stranger calling himself the Doctor, who escorts her out of the building before returning inside -- and blowing up the store. The Doctor disappears, leaving Rose to wonder what unspeakable evil could have manifested itself in the animated plastic dummies... one of whose arms she still carries with her.

Later in her flat, while her mother Jackie (Camille Coduri) makes hasty plans to take advantage of her daughter's misfortune financially, Rose's boyfriend Mickey (Noel Clarke) futilely attempts to take her to the pub, and then disposes of the arm. The next morning, Rose spies the Doctor investigating the cat-flap into the apartment; he's tracking a signal, which he fails to adequately explain until the plastic arm, which somehow crawled out of the rubbish bin and came back to the flat, suddenly takes on a life of its own and attempts to kill them both. The Doctor neutralizes the signal coming to the mannequin arm and Rose follows him out to the car park, learning that the Doctor is somehow here to stop a war. He takes leave of her, disappearing in a strange blue box... 

Curious about this mysterious Doctor that has now entered her life twice, Rose investigates on the Internet, discovering the website of a man named Clive (Mark Benton). She and Mickey drive to his neighborhood, and Rose meets the conspiracy theorist who has evidence that the title "Doctor" is somehow an honorific that has been passed down through the ages, possibly father to son, and that the image of this man she's met has popped up in images ranging from the Kennedy assassination to the sailing of the Titanic. Meanwhile, outside, a neighbor's wheelie bin starts acting strangely, prompting Mickey to investigate... but soon, the rubbish bin takes on a life of its own and devours him, replacing him with a duplicate with strange hair and stranger behavior. 

Later at a restaurant, the duplicate starts questioning an oblivious Rose about the Doctor's plans. The two are found by the Doctor, as the Mickey doppleganger starts tearing up the place attempting to attack them. The Doctor takes Rose outside where the TARDIS awaits, and after she panics, Rose enters the TARDIS, incredulous about its internal size and the fact that the Doctor is really an alien. The TARDIS dematerializes, reappearing on the bank of the Thames. The Doctor tells her that Mickey's duplicate is controlled by the Nestene Consciousness, a powerful alien entity interested in the Earth because of the toxins in the atmosphere, and because it's somehow lost its own planet in a massive war. However, in order to take control of Earth it will have to control its animated plastic warriors through the use of a massive transmitter... which Rose deduces is the London Eye wheel. The Doctor has his own recourse -- a vial of a material he calls anti-plastic -- but first, he wants to reason with the Consciousness. 

Below the Eye, the Doctor approaches the Nestene Consciousness, an animated vat of living plastic, which chastises him for the vial of anti-plastic and attacks the Doctor because it recognizes the TARDIS. The Consciousness transmits the activation signal through the London Eye, bringing to life thousands of mannequins in London who begin attacking people in public places, including killing Clive in a shopping mall and attacking his family and Rose's mother. Mickey, who was kept alive to keep the doppleganger's shape cohesive, begs Rose to take him away and leave the Doctor behind. But Rose, realizing she can't abandon the Doctor, comes to his rescue by plunging the two mannequin guards into the vat along with the anti-plastic, destroying the Nestene Consciousness and ending the signal that animates the plastic dummies. 

Later, the TARDIS drops off Rose and a cowering Mickey in the alley near her flat. The Doctor, obviously taken by his bright new friend, invites Rose to join him, offering her travel anywhere in the universe. She turns him down, albeit hesitantly, needing to take care of her mother and Mickey. But when the Doctor hastily returns again, wondering if he'd mentioned the TARDIS travels in time as well, Rose smiles, politely kisses Mickey on the cheek and heads for the TARDIS door, toward new adventures...