Series 2 (2006)
Episode title: School ReunionFeaturing: Tenth Doctor
Companions: Rose Tyler, Sarah Jane Smith, Mickey Smith
First shown: 29th April 2006
Related articles: Krillitanes, K9
Guide: On present day Earth, Mickey contacts the Doctor and Rose with suspicious goings on at a local school, Deffry Vale. The Doctor and Rose decide to investigate and the Doctor goes in undercover as a physics teacher under the alias, John Smith, while Rose goes to work in the kitchens. Mr. Finch, the schools headmaster, has introduced some radical changes to the school, one of which including the provisions of free lunches provided by the school with special chips, to which the Doctor and Rose both relate mysterious goings on to. Rose observes that the chip oil has an adverse react to her fellow kitchen colleagues, while the Doctor is astounded by the uncommon intelligence by one of his students, and notes that the chips appear to be making them more intelligent. Meanwhile, the schools successes have also attracted the attention of the media, in particular the attention of an investigative journalist, Sarah Jane Smith. The Doctor feigns ignorance as to his identity when Sarah Jane remarks that she used to know a John Smith, many years ago, until Sarah Jane finds the TARDIS in the night and the Doctor is forced to admit his identity.
Sarah expresses anger at the Doctor that he abandoned her in Aberdeen, miles away from her home in South Croydon, but gets over it quickly enough and meets Rose and Mickey. Sarah and Rose don’t get along at first as they investigate the school, where the find 13 hanging bat creatures sleeping in Mr. Finch’s office. Outside, Sarah reveals the mark 3 K9 in the boot of her car which the Doctor repairs and identifies the chip oil as Krillitane oil. Rose however, confronts the Doctor about past companions, as she didn’t know he’d had others before her, but he sadly remarks that while she can spend the rest of her life with him, he cannot spend the rest of his life with her, and so he must move on and remain aloof. The following day, the Doctor confronts Mr. Finch about his findings, to which Mr. Finch admits that he and his fellows are Krillitanes, and attempts to subvert the Doctor, though the Doctor doesn’t let him succeed. Meanwhile, Rose and Sarah, now getting on better, attempt to unlock the programming on the school’s computers while Mickey is left outside in the car with K9, remarking that he’s the new tin dog in the Doctor’s life.
The Doctor helps Rose and Sarah and discovers that the Krillitanes are using the students’ enhanced intelligence levels to solve the Skasis Paradigm, the theory of everything that would allow the Krillitanes the power to control the whole of time and space. As the Paradigm comes close to being solves, the Krillitanes seal the exits of the school, trapping everyone inside while Mr. Finch tries to proposition the Doctor a second time, offering him the chance to save the Time Lords and override the human mortality that prevents him from staying with his companions for ever. The Doctor likes the sound of what Mr. Finch tells him, but with Sarah Jane’s counselling, the Doctor refuses and the duo run from Mr. Finch. Meanwhile, Mickey uses the car to break into the school by smashing through the doors, and begins to unplug the computers, freeing the children who make their escapes. The Doctor leads the Krillitanes into the kitchen, where K9 stands ready. When the Krillitanes are in the kitchen, K9 detonates the chip oil, covering the Krillitanes in their own oil, which has become hazardous to them through their evolution process, causing the Krillitanes to explode, destroying the kitchen and the school.
Outside the TARDIS, the Doctor offers Sarah Jane the opportunity of travelling with him once more, but she declines and supports Mickey’s request to join the TARDIS crew when he asks if he can go with the Doctor and Rose. Sarah asks Rose to stay with the Doctor and if she needs help then she should find her. Sarah Jane then gets the opportunity to have a proper good bye with the Doctor, as opposed to being abandoned like last time, while the Doctor leaves her a parting gift of a brand new K9, which was also equipped with gadgets such as numerous Sonic Lipsticks, and a wristwatch for detecting alien life forms on Earth.