The episode starts with a thirteen year old girl, Maria Jackson (Yasmin Paige), and her recently divorced father Alan (Joseph Millson) moving into a house opposite journalist and former time-traveller Sarah Jane Smith (Elisabeth Sladen). The night after they have moved in, Maria is woken by an ethereal light emanating from Sarah Jane's house, which she discovers, to her amazement and later horror, to be Sarah conversing with a butterfly-like alien species.
The next morning, her neighbour Kelsey Hooper (Porsha Lawrence Mavour) visits and welcomes her. She invites Maria into town, using the free "Bubble Shock!" bus to travel there and tour the factory. Once they arrive at the factory, they are lead to a security scanner, which surreptitiously collects their DNA to transfer to an "Archetype" (Tommy Knight) under the supervision of the factory's owner, Mrs Wormwood (Samantha Bond).
Sarah Jane, having overheard the girls making plans, follows them to the factory and interviews Mrs Wormwood, and how she was able to get approval for the drink so fast, and why the Bane, an ingredient unique to the drink, was "resisting" analysis, to which she is told that all that Bubble Shock! is doing is satisfying the needs of the Western world. On Sarah's way out, she is almost killed by Wormwood's secretary.
Kelsey wanders from the tour and attempts to phone her friend, but disturbs an unknown beast, the Bane Mother, to the annoyance of the staff, to which Wormwood orders the alarms switched off and Sarah Jane killed. Maria attempts to phone Kelsey, but sets off the alarms again, causing the Archetype to escape, transferring the focus upon him. Maria, while escaping, encounters him, who just mimics her, and they escape into a women's bathroom. Sarah Jane then enters, and although they are surprised to see each other, they manage to escape the factory