Young Maria Jackson and her recently divorced father, Alan, have moved into a house opposite Sarah Jane Smith on Bannerman Road. That night, Maria is awakened by a bright light which she follows to Sarah Jane's garden, and finds there a glowing alien. As it disappears into the night sky, a terrified Maria runs home and locks the front door.
The next morning, local girl Kelsey Hooper arrives to welcome the new family and offers to take Maria into town. Kelsey tells her about the free tours given at the Bubble Shock! factory, a new and popular brand of soda, containing Bane, an ingredient said to be "all natural", which tastes foul to 2% of the population, which conveniently Maria is part of. Mr. Jackson attempts to introduce himself to Sarah Jane, but she overhears the girl's plans and gives chase in her car.
At the factory, all the guests are scanned, and the information taken from them is directed to a secret lab in the building. In that lab, a boy called the Archetype lies on a table, with a woman named Mrs. Wormwood overseeing the experiment.
Sarah Jane pulls into the parking lot and tries to enter the factory with her Sonic Lipstick, but is quickly found and escorted to Mrs. Wormwood's office. There Mrs. Wormwood deflects her attempts to find out exactly what the 'organic' ingredient in Bubble Shock is.
Kelsey slips away from the tour to make a phone call. Her mobile sets off alarms throughout the building. Davey, the tour guide, sends everyone outside and hurries off to look for Kelsey. She's trapped in a corridor under an alien that looks like a giant eyeball surrounded by tentacles. Davey refers to it as his mother and smashes her phone to interrupt the signal.
Sarah Jane escapes an assassination attempt on her way out of the factory and runs deeper into the corridors.
Maria, trying to find Kelsey, accidentally sets off the alarms again. The monitoring equipment attached to the Archetype malfunctions and he wakes, ripping out his IVs and running for it. Maria meets him in a corridor; he can only repeat what she says. She takes him to hide in the girl's bathroom. Sarah Jane happens across them moments later and they escape through the window to the carpark.
Back at Bannerman Road, Sarah Jane takes the Archetype into her home, sending Maria away. The boy answers all Sarah Jane's questions but can't tell her much; he was born running, he has no memories before meeting Maria, he doesn't know where he came from or who taught him to speak and read. Sarah Jane's scanner reads him as perfectly normal but only six hours old.
A voice from upstairs calls Sarah Jane. She orders the boy never to go up there.
Kelsey is in Mrs. Wormwood's office. Wormwood and Davey attempt to question her, but can't penetrate the babble and pop culture references. Mrs. Wormwood returns to her true form and uses a telepathic attack to lift the answers she wants directly from Kelsey's mind, removing her memories of the incident at the same time. Learning from Kelsey that Sarah Jane lives alone on Bannerman Road, she sends Davey to take care of her.
Kelsey goes to Maria's, telling her about the 'muffin' who brought her home. Maria runs to Sarah Jane's to warn her, but Davey, in his true form - something like a giant squid - is already attacking. Sarah Jane hurries the children up the stairs, ordering them to wait while she retrieves a spray from the attic. It drives Davey off. Kelsey sneaks upstairs and the others follow, finding the attic full of relics from Sarah Jane's alien adventures. The Archetype examines a communicator, apparently fascinated by it.
At the Bubble Shock factory, Mrs. Wormwood proclaims that, as penalty for failing, Davey will be eaten by the Bane Mother.
Sarah Jane tells the kids a simplified version of her history. She also introduces them to K9, who's protecting the Earth from a black hole and can only speak to her briefly at long intervals. The Archetype notices that Sarah Jane's scanner is picking up alien presence - she traces it to Kelsey's bottle of Bubble Shock, which contains a chemical secreted by the Bane Mother. In essence, anyone who drinks Bubble Shock is drinking a Bane.
Sarah Jane uses her alien computer, Mr. Smith, to call Mrs. Wormwood at the factory using a long access code. She orders Mrs. Wormwood to leave the planet, but Wormwood simply tells her to bring it on.
Mrs. Wormwood starts the conversion process. Anyone who has drunk Bubble Shock falls under her control and start hunting down normal people. Kelsey chases Sarah Jane, Maria and the Archetype from the attic. Out on the street, Alan attempts to grab Maria. Sarah Jane bundles her into the car with the Archetype and heads back to the factory.
Faced with a deadbolt sealed door, Sarah Jane uses the Bubble Shock bus to break through a wall. Mrs. Wormwood welcomes her in and thanks her for returning the Archetype. He was created from the scans of ten thousand visitors to the factory, with all their strengths and weaknesses. He was designed to tell them how to alter Bubble Shock to affect the two percent currently immune. However, now that the plan has been moved up, he is unnecessary. The boy collapses.
Sarah Jane begs for his life, but Mrs. Wormwood doesn't care. Maria attempts to stop her with the signal from her mobile, but it's not strong enough. The boy produces the communicator - the signal it produces will be so much stronger. Mrs. Wormwood points out that he doesn't know their frequency, but he does. He saw Mr. Smith display it earlier and he remembers it.
The Bane Mother is hurt by the signal and the factory begins to shake. Sarah Jane, Maria and the boy make a run for it, while Mrs. Wormwood escapes on a service lift. Sarah Jane and the kids are safely outside when the factory explodes. The Bane's control on the boy is lifted.
Back at home, Maria slips away from an argument between her parents to join Sarah Jane in her garden. Kelsey is refusing to talk to either of them, busy convincing herself the whole thing never happened.
The boy, now dressed in modern clothes, comes to join them. Sarah Jane has had Mr. Smith create adoption papers putting him in her custody. The only thing left to do is give him a name. They consider Alastair and Harry before settling on Luke.
They sit together, studying the stars above them.
- Angelic Aliens: The alien poet who visits Sarah Jane. This one seems benevolent, and is thus a more straight example of the trope than the previous example that appeared in the Torchwood episode "Greeks Bearing Gifts".
- Blank Slate: Luke, at first.
- Bring It: Sarah Jane attempts to get Mrs. Wormwood to leave peacefully. It doesn't work.Mrs. Wormwood: In the language of your young ones, bring it on.
- Call-Back: Sarah Jane breaks into a sealed building by driving a vehicle through it, like Mickey did in the last story she appeared in. She gets the idea after thinking back over her adventures with the Doctor for inspiration.
- Car Meets House: The factory entrance has a deadlock seal, meaning that Sarah can't use her sonic lipstick. So she drives through the factory wall in the Bubble Shock! bus.
- Chuck Cunningham Syndrome: Kelsey Hooper makes her one and only appearance in this story. It has never been stated if Kelsey was intended to return or not, and the story itself leaves it unclear as to if she would or not. Her spot in Sarah's "gang" was later occupied by Clyde Langer. No clarification of the matter was ever officially given by the production team.
- Continuity Nod:
- Photos of the Brigadier and other UNIT personnel are seen among Sarah Jane's stuff.
- The names Sarah Jane suggests for Luke include Harry and Alistair, the names of two of the UNIT personnel she used to hang out with in Doctor Who.
- The alien Sarah Jane meets in her garden at night is the same species as one that appeared in the Torchwood episode "Greeks Bearing Gifts".
- Sarah Jane's distaste for soda pop comes up again.
- Dropped After the Pilot: Kelsey Hooper, who is set up as Maria's friend and possibly a member of Sarah Jane's newly formed alien hunting squad (despite outright denying the extraterrestrial things she witnessed), is never mentioned again after the pilot, and her role as the "cool one" is given to Clyde, who ends up sticking around the whole series and providing the Opening Narration. The producers claimed that this was because the cast of the pilot "skewed too female" and they wanted to redress things, although it was widely reported that the actress was difficult to work with on set.
- Early Instalment Weirdness: In addition to Kelsey, above, Sarah Jane drives an elbow into one of the guards. Later stories have no mention of her having ever studied self-defence (although it's hardly surprising).
- Foreshadowing: The girls in a Bubble Shock commercial say "Contains Bane!" right before Maria turns off the TV.
- Genetic Memory: Luke.
- Hand Wave: Why are Blue Peter being used in an advertising montage despite the BBC’s taboo on advertising? The drink is that good (to 98% of the population).
- Happily Adopted: Luke is adopted by Sarah Jane, and both are pleased about the arrangement.
- May Contain Evil: The Bubble Shock.
- Mythology Gag: Luke is almost named after two other companions of the Doctor that Sarah Jane knew.
- Screaming Woman: Kelsey.Luke: Hello, Maria. Hello, screaming girl.
- Shout-Out: When reading her mind, Mrs. Wormwood believes that Kelsey worships something called the "Holy Oak," only to realize she enjoys Hollyoaks.
- Socially Awkward Hero: Sarah Jane, at first, though she grows out of it.
- Stacy's Mom: Well, Stacy's Dad. Kelsey finds Maria's father attractive, which Squicks Maria out.
- Take That!: Bubble Shock may be a parody of the controversy surrounding Sunny Delight, an orange-flavoured soft drink that was deceptively marketed to suggest that it was healthier than it was, or that it was actual orange juice.
- There Are Two Kinds of People in the World: "People who panic, and then there's us."
- We Will Meet Again: Mrs. Wormwood promises Sarah Jane this.
- The X of Y: Standard fare for the Whoniverse but would be the first of many such episode titles in the series.
- You Have Failed Me: Davey faces Mrs Wormwood regarding his failure. Despite begging for mercy and proclaiming that Sarah has terrible weapons, Davey is reminded that there is no mercy for failure in the Bane world. Assuming her true form, Mrs Wormwood remarks that Davey will be fed to the Bane Mother in accordance with the penalty. Davey screams as she looms over him...