Rose Tyler is a shop assistant at Henrik's, a department store in present-day London. One evening, she is about to go home when the security guard passes her a packet containing lottery money, presumably to be given to whoever runs the staff syndicate. Rose goes to the basement to find Wilson, the chief electrician, but he is nowhere to be found. She hears a noise and goes to see what it is, entering a room filled with plastic store dummies. The door slams shut, locking her in, and the mannequins come to life, backing her into a corner. Before the lead one can strike her, someone grabs Rose's hand: a tall, strange-looking man in a leather jacket and crew cut, who tells her to run.

Rose and the stranger burst through another set of doors and race down the corridors of the basement, pursued by the dummies. They reach the lifts, and a mannequin's arm lunges through the closing doors. The stranger grapples with the arm, and with a jerk, yanks it off. The doors shut, and the stranger tosses the now lifeless plastic arm to Rose. She still believes that it is some kind of student prank, but the stranger shakes his head. They are living plastic, and Wilson is dead.

Reaching the ground level, the stranger disables the lift buttons with a pen-like device that projects a high-pitched whine. The stranger explains the plastic creatures are being controlled by a relay on the roof, and he is going to destroy it with an explosive device. He ushers Rose out and before he goes back into the building, he introduces himself as the Doctor. He asks for her name, and she tells him it is Rose. "Nice to meet you, Rose," the Doctor says, adding, "Run for your life!" Rose reaches the other side of the street, still holding onto the arm, and looks up at the Henrik's building as the top floors and roof explode. She runs off in the confusion, not noticing an anachronistic police box standing off to the side.

Later, Rose watches the report of the fire on television at her council flat, her mother Jackie telling friends on the telephone about her daughter's narrow escape. Rose's boyfriend Mickey arrives, expressing concern, but she tells him she is fine. Rose asks him to dispose of the plastic arm, which Mickey tosses in a rubbish bin at the foot of Rose's block of flats when he leaves.

The next morning, Jackie suggests Rose take a new job or ask for compensation. Rose hears someone at the door, and peeks through the cat flap to see the Doctor's face. The Doctor seems as startled to see her — he appears to have gotten the wrong signal. Rose drags him in, wanting answers so she can tell the police. Jackie is fascinated by the new arrival and tries, awkwardly, to seduce him. The Doctor simply says "No," and steps away, to Jackie's irritation.

Rose fixes coffee while the Doctor waits in the living room, peering at his own reflection in the mirror as if for the first time and looking at everything. The Doctor hears a scuttling behind Rose's sofa, and when he looks, the plastic arm which has somehow returned leaps up to strangle him. Rose thinks the Doctor is just play acting with the arm until it attacks her. Jackie, drying her hair in the other room, hears nothing as the Doctor and Rose crash around with the arm. Managing to pull it away from Rose, the Doctor uses the same pen-like device — his sonic screwdriver — to shut it down.

Rose follows the Doctor as he leaves. The Doctor tells her that the plastic arm was fixed on him as a target and only attacked Rose because she got in the way. It was controlled by something that projected life into the arm by thought, and he simply cut off the signal. Their purpose is to destroy the human race. Rose does not believe him, but the Doctor notes that she's still listening.

She asks the Doctor once again who he is as he walks towards a police box. The Doctor tells her that it's like when you are a child and are first told the world revolves. You cannot quite believe it because everything looks like it is standing still. He takes her hand, telling her that he can feel it, the Earth turning, the world itself spinning around the Sun, everyone falling through space and clinging to the surface of this tiny planet, and if they let go... That's who he is. The Doctor tells Rose to forget him and go home. She walks away but when she hears a strange, grating sound and runs back, the Doctor and the police box have disappeared.

Rose goes to Mickey's flat and uses his computer to search the Internet for information about the Doctor. She finds a website, "Who is Doctor Who?", which features a picture of the Doctor together with an appeal for anyone who has seen him to contact the site's maintainer, a man called Clive. Rose goes to see Clive at his house in suburban London while Mickey waits, suspicious, in the car outside.

In his study, Clive tells Rose that the name of the Doctor keeps cropping up through the years in diaries, journals and conspiracy theories. No names, just the Doctor, perhaps a title that is passed along from father to son. He shows her photographs that show the Doctor in the crowd at the Kennedy assassination, at Southampton on the eve of the Titanic's sailing, and in a drawing from 1883 that was washed up on the coast of Sumatra after the eruption of Krakatoa. Clive explains that the Doctor is a name woven throughout history, bringing storms in his wake, death his constant companion.

As Mickey waits impatiently outside, he goes to investigate a plastic rubbish bin that he saw moving on its own, but it is empty. As he tries to return to the car, he finds his hands stuck to the lid, the plastic stretching but not letting him go. He is yanked into the bin, which shuts with a loud belch.

Clive warns Rose that they are all in danger. He believes that these pictures all portray the same man, and that the Doctor is an immortal alien. Rose thinks Clive is delusional. She returns to Mickey's car and tells him to drive somewhere for lunch, not realizing he has been replaced by an auton.

At the restaurant, "Mickey" wants to know more about the Doctor. The auton isn't quite perfect, and stutters, but she does not want to discuss the Doctor, saying she thinks he is dangerous. A waiter offers Mickey and Rose champagne. "Mickey" says they did not order any — then looks up and sees the waiter is the Doctor. The Doctor pops the cork on the bottle, sending it flying into "Mickey"'s head, which absorbs it, then spits it out. "Mickey" morphs his hand into a heavy spade-shape, slicing the table in half. The Doctor gets "Mickey" in a choke hold and manages to pull his head off. The headless auton rampages through the restaurant. Rose tells the other patrons to run, then follows the Doctor, who is holding onto the head.

Reaching the yard, the Doctor seals the door behind them with the sonic screwdriver, but the auton is soon pummeling it with inhuman force. The Doctor suggests they go into the police box standing there. Rose incredulously follows him in, but stops short as she sees the interior. She runs around the box, assuring herself of its ordinary size before going in again just as the auton breaks through.

Inside the much larger interior of the ship, the Doctor assures Rose that nothing can get through the doors. He attaches the plastic head to the console, telling Rose that the head can be used to trace the signal back to the source. Rose asks if the ship and the Doctor are alien and he answers yes to both questions. The ship is his TARDIS — Time and Relative Dimension in Space. Rose chokes back a sob, and asks if "they" have killed Mickey. The Doctor is taken aback as he had not considered this, and Rose is shocked he has not. "Mickey"'s head starts to melt, and the Doctor frantically runs to the console, trying to lock on to the signal before it fades. The TARDIS starts up, and then stops.

The Doctor rushes through the doors, with Rose shouting that it is not safe. When she follows him, however, they are not in the yard anymore but on the banks of the River Thames. The Doctor says the TARDIS is able to disappear and reappear in a different place. He is angry because he has lost the signal. Rose is worried about the automaton, but the Doctor says it would have melted along with the head. Rose mutters that she is going to have to tell Mickey's mother that he is dead, and when the Doctor asks who, Rose realizes the Doctor has forgotten Mickey again. They have a confrontation about his lack of empathy, the Doctor shouting that he is more concerned about saving the life of "every stupid ape blundering about on top of this planet." Rose asks if the Doctor's an alien, why he sounds like he's from the North. The Doctor retorts that lots of planets have a North. This seems to defuse the tension.

Rose stares at the exterior of the TARDIS and asks what a police public call box is. The Doctor, cheerful again, explains that it is a disguise, a telephone box for the police from the 1950s. Rose, curious again, asks what the living plastic creatures have against the Earth. The Doctor replies that they love the Earth because it has plenty of pollutants. The Nestene Consciousness — the intelligence animating the plastic — lost its food supply during a war, when all its protein planets rotted. Earth is dinner. Rose asks if there is any way to stop it, and the Doctor produces a clear cylinder of blue liquid. "Anti-plastic," he announces.

However, the Doctor has to find the Consciousness. He wonders aloud that the transmitter to control the plastic has to be huge, and round… Rose indicates behind him, and after a few puzzled glances over his shoulder the Doctor notices the London Eye. Hand in hand, they run across the bridge to it. Rose spots a hatchway that leads below the Eye, and they both go below to find a giant vat of pulsing, molten plastic — the Nestene Consciousness. The Doctor wants to give it a chance and applies for an audience, citing Convention 15 of the Shadow Proclamation. The vat roars its assent in an unintelligible alien language. Rose spots the real Mickey, sitting terrified on one of the walkways. The Nestenes kept him alive to maintain the replica.

The Doctor tells the Consciousness to leave Earth, brushing aside its claims of constitutional rights and characterizing its actions as an invasion. The Doctor pleads on humanity's behalf — they are primitive, but capable of much more. However, two autons grab hold of the Doctor, one removing the container of anti-plastic from his jacket.

The Doctor protests that the vial was just insurance and he is not their enemy. The Consciousness responds by unveiling the TARDIS, and makes an accusatory howl. The Doctor admits that it is his ship, but says that it was not his fault — he fought in the war, but he could not save the Nestenes' world. The Consciousness does not believe the Doctor and goes to the final phase of the invasion. Bolts of electricity stab up across the London Eye as it pulses a signal across London. Rose tries to warn her mother on her mobile phone, but the call breaks up and Jackie, who is about to enter a shopping centre called the Queen's Arcade, cuts it off.

Clive and his family are also at the arcade when the shop dummies come to life, crashing through the windows. Clive realizes that all the stories he has read are true, just as a mannequin's hand flips open, revealing a weapon. He looks on sadly as the auton shoots him point-blank. People scream as the automatons start killing everyone in sight. Beneath the Eye, the stairs back up to the surface collapse. Rose and Mickey rush to the TARDIS, but the door is locked. As she and the Doctor lock eyes helplessly, outside in the streets the massacre continues. Jackie is trapped by a group of mannequins in wedding dresses, who prepare to shoot her.

Mickey tells Rose to abandon the Doctor, but Rose rushes up a flight of stairs to a chain on the wall. She may have no A-levels, no job and no future, but she has a bronze medal in under-sevens gymnastics. She frees the chain with a blow from a fire axe, and swings across to knock the auton holding the anti-plastic over the railing. While the Doctor flips the one holding him over as well, the anti-plastic falls into the vat, causing the Consciousness to writhe in pain. The Eye stops transmitting, and the autons across London jerk spastically and drop, including the ones menacing Jackie, leaving the streets scattered with debris and the dead. The Nestenes' vat explodes as Rose, Mickey and the Doctor enter the TARDIS and it dematerialises.

The TARDIS rematerialises on a side street, Mickey stumbling out, still terrified. Rose calls up her mother on her mobile phone and smiles in relief as she hears Jackie's voice. Rose hangs up without saying anything, and tells the Doctor that he would have been dead if not for her. The Doctor smiles from the TARDIS doorway in agreement and thanks her. He then offers to take her with him to see the universe — Mickey is not invited. Rose asks if it will always be this dangerous, and the Doctor gleefully answers yes. Rose hesitates but declines, saying that she has to find her mother and look after Mickey. The Doctor nods, disappointed and closes the door. The TARDIS dematerialises with a rush of wind filling the empty space where it was.

As Mickey and Rose turn to leave, the TARDIS appears again. The Doctor pops his head out and asks Rose if he had mentioned that the TARDIS also travels in time. Rose smiles, turning to Mickey to kiss him goodbye, then runs happily into the TARDIS.

Cast

• Doctor Who — Christopher Eccleston
• Rose Tyler — Billie Piper
• Jackie Tyler — Camille Coduri
• Mickey Smith — Noel Clarke
• Clive — Mark Benton
• Caroline — Ellie Garnett
• Clive's Son — Adam McCoy
• Autons — Alan Ruscoe, Paul Kasey, David Sant, Elizabeth Fost, Helen Otway
• Nestene Voice — Nicholas Briggs