School Reunion was the third episode of the second series of BBC Wales Doctor Who. It continued from the prelude established in Tardisode 3.
The episode marked the return of Sarah Jane Smith and K9 Mark III, both having last appeared on-screen in 1983’s The Five Doctors. K9 Mark III was destroyed and replaced by a newer model at the end of the episode. Months after this episode aired, rumors of a spin-off series with Sarah Jane were confirmed by the BBC and The Sarah Jane Adventures premiered on BBC One on 1 January 2007.
At Deffry Vale High School, the headmaster, Mr Finch, notices a student waiting outside his office. She has a headache, and cannot simply go home because she lives in an orphanage. Mr Finch offers his sympathies that there is no-one to miss her and invites her into his office; it is nearly time for lunch. The door closes, then there is a flap of wings, and the girl screams.
“John Smith” and Rose have gone undercover in the school. He teaches a physics class. He asks a few simple questions. Only an intelligent student called Milo can answer. The Doctor advances to higher levels of knowledge, finally asking how to travel faster than light. Milo answers every question without missing a beat.
Meanwhile, Rose is working undercover in the cafeteria. At lunch, she complains to the Doctor about the last two days. He mentions that it was Mickey who alerted them to something odd going on and rightly so. Everyone at the school is well-behaved and there is something odd about the chips. Rose eats a few, saying she enjoys them. The school menu has been designed by Mr Finch himself to improve concentration and performance. Another teacher, Mr Wagner, approaches Melissa, one of the students. He tells her Milo has failed him, so she is being moved to the top class. He also summons another student, Luke, but not Kenny, who is not allowed to eat the chips. The Doctor observes all this. He looks up and sees Mr Finch gazing down on the cafeteria floor, watching everything.
In the kitchen, Rose watches the other kitchen staff, all wearing gloves and face masks, bringing in a large barrel. One of the dinner ladies warns them not to spill a drop. Mickey calls Rose on her mobile phone, telling her about the massive UFO activity he has discovered around the area. However, his investigations are being blocked by something called Torchwood. Rose, in turn, tells him the kitchen staff were all replaced three months ago with new personnel. As they speak, the barrel slips, spilling something on one of the staff, who starts to burn. The rest usher her into a side room. Rose starts to phone for an ambulance, but is told not to worry, she is all right, even as Rose hears screams and lots of smoke billows out of the side room. Rose glances down at the barrel, which is leaking a golden, oily substance.
In the maths classroom, Mr Wagner tells the children at their computers to put on their headphones. The screens flicker on. The monitors display a green, rotating cube with rapidly scrolling, alien-looking symbols and seemingly random text on the right. The children type on their keyboards with incredible speed.
Mr Finch escorts a journalist, Sarah Jane Smith, around the school. Sarah Jane has been assigned to write a profile on him. Finch explains that one of the policy changes he has made is free — but compulsory — school dinners. In the staff room, the Doctor is speaking to Mr Parsons, head of History, who tells him of the extraordinary knowledge of his students since Finch became Headmaster. One of his students has given him the exact height of the walls of Troy in cubits. Also, the day after Finch arrived, seven teachers came down with flu, and were replaced by strange new ones. The one the Doctor replaced hadn’t had the flu. She had resigned when she won the lottery, despite the fact that she never played, claiming the ticket was posted through her door at midnight. Mr Finch brings Sarah into the staff room. When the Doctor sees her, he smiles delightedly at unexpectedly seeing his old friend, but introduces himself as John Smith. Sarah remarks that she once knew a man who went by that name. When she learns “Smith” is a new teacher, she asks if he has noticed anything odd. She has lost none of her inquisitive nature, and the Doctor is elated, although he does not reveal his real identity to her.
As the Doctor wanders the halls in a slight nostalgic haze, Kenny goes into the Maths room. He is shocked to glimpse a bat-like creature under one of the desks. It transforms rapidly into Mr Wagner. Wagner tells Kenny to leave and the boy beats a hasty retreat.
That night, Sarah Jane Smith breaks into the school to explore, even as the Doctor, Rose and Mickey do the same. The Doctor sends Mickey to the maths room and Rose to get a sample of the oil, while he checks the headmaster’s office. There are sounds of flapping and the occasional shriek. Winged shadows flit across walls.
Sarah Jane, trying to break into Mr Finch’s office, notices she is being watched. She enters a store room — where she finds the TARDIS. Stunned at seeing the ship again, she backs out of the room into the gym, where “John Smith”, now wearing his long coat, is waiting and says, “Hello, Sarah Jane.” Sarah Jane manages to say, “It’s you…Doctor! Oh, my God, it’s you, isn’t it? You’ve regenerated…”
The Doctor replies that he has done so “about half a dozen times since we last met.” She says he looks “incredible”, and he says she does too, but she dismisses it being true for herself and says she has grown old. She then reveals she had waited for him and thought he had died, and in response, the Doctor speaks to her of the Time War for the first time: “I lived. Everybody else died.”
They hear a piercing scream and run towards the sound, meeting Rose along the way. The Doctor introduces the two and Sarah Jane comments on Rose’s youth. The scream turns out to be Mickey, who opened a cupboard, only to be covered in shrink-wrapped rats. Sarah suggests the rats are for dissection, but Rose retorts that rat dissection hasn’t been performed in schools for years, making a snide dig at Sarah’s age. As they head for Finch’s office, and Sarah Jane and Rose begin to bicker, Mickey laughs and tells the Doctor, “The missus and the ex — welcome to every man’s worst nightmare!”
The Doctor suggests that the rats may be food for something. When they enter Finch’s office, they find what that “something” is thirteen large, bat-like creatures hanging from the ceiling, asleep. They back out hurriedly, but as the door shuts, one of the creatures wakes and shrieks. Outside, the Doctor says they have to go back in so he can use the TARDIS to analyse the oil sample Rose procured. Sarah tells the Doctor she may have something that can help him. To the Doctor’s excitement, in her car boot is an inactive and rusty K9 Mark III, with one of his side panels missing. Sarah explains that one day it had just stopped working and she could not repair its advanced technology.
Not knowing that they are being trailed by Mr Finch and another bat-creature, they go in Sarah’s car to a nearby café, where the Doctor repairs K9. Mickey teases Rose about her jealousy, while Sarah asks the Doctor why he never came back for her. In an intense moment, the Doctor tries to brush it off, saying that she was getting on with her life. Sarah replies that he was her life. The hardest thing was adjusting back to mundane life after all she had seen. She asks him why he could not have come back. The Doctor looks dour and does not reply.
K9 comes to life, and recognizes the Doctor, who smears some of the oil sample on its eye sensor. K9 determines it is Krillitane oil. The creatures are Krillitanes, a composite species who take the best physical parts of other species they conquer. The Doctor did not recognize them because they had looked different when he had last seen them. He realizes that they are doing something to the children.
As they leave the café, Rose asks the Doctor if Sarah Jane is her future, that she will be left behind like all his other companions. The Doctor tells her he did not go back for Sarah because it would have been too hard: “I don’t age. I regenerate. But humans decay, you wither and you die. You can spend the rest of your life with me. But I can’t spend the rest of mine with you. I have to live on, alone. That’s the curse of the Time Lords.”
Mr Finch hears the phrase “Time Lords” and sends the other Krillitanes to swoop over them, although they do not harm anyone.
The next day they all return to the school. The Doctor sends Rose and Sarah to discover what is inside the computers, and Mickey to stay in the car with K9 as surveillance — a task Mickey compares to being “sent to the back of the class with the safety scissors and glitter”. The Doctor himself is going to have a word with Mr Finch. They confront each other at the swimming pool. Finch confirms he is a Krillitane named Brother Lassar and the wings are a recent addition to their form. What the Doctor sees as human is just a morphic illusion. Surprised to see a Time Lord, Lassar calls them a race of pompous, dusty senators, afraid of change and chaos and now all but extinct. He can sense that the Doctor is different, but still refuses to reveal his plans, challenging him to work it out. Lassar says that they are not enemies. The Doctor quietly replies that he had much more mercy when he was younger. This is their only warning. Lassar smugly promises that the next time they meet, the Doctor will join with him.
Working on the computers, Sarah and Rose argue about who has had more experience time traveling, yelling the names of the different monsters they have met. Sarah Jane settles it when she mentions she met the Loch Ness Monster, but they soon realize the argument is pointless and bond by comparing notes on the Doctor (Sarah Jane is very amused to hear from Rose that the Doctor still strokes parts of the TARDIS), bursting into laughter when he enters and confusing him.
Lassar tells the other Krillitanes that they are moving to the final phase. The school will be sealed and they will become gods. Even though it is break time, the intercom calls all pupils to class and the staff to the staff room. All the pupils appear strangely happy that the break has ended early, except Kenny, who hesitates, but eventually follows the others inside. The Krillitanes begin by devouring the rest of the staff.
In the maths room, the Doctor finds the computers fixed with a deadlock seal which the sonic screwdriver cannot breach. Lassar seals all of the school’s exits while Mr Wagner activates the computer program which the children begin working on again. Kenny cannot get out of the school, but he attracts Mickey’s attention. Mickey reactivates K9, asking it if it has some way to get in the school. K9 reminds him they are in a car.
Rose, Sarah and the Doctor watch the symbols flash on a large screen. The Doctor works out that the Krillitanes are trying to solve the Skasis Paradigm. He explains that the Paradigm is the God-Maker, the Universal Theory; whoever solves it can control the building blocks of the universe — all of time and space. The Krillitanes are boosting the children’s intelligence with the oil, using them and their imaginations as a giant processing device. Lassar appears at this point, asking the Doctor to join them, tempting the Doctor with the ability to change the universe, to save everyone, even restore the Time Lords. He offers Sarah and Rose the chance to travel with the Doctor forever, never growing old. The Doctor appears tempted, but Sarah tells him that pain and loss define them as much as happiness or love. Everything has its time and everything ends, whether a world or a relationship. The Doctor picks up a chair and hurls it at the screen, smashing it. He tells Rose and Sarah to get out.
After Mickey voices his frustration at being reminded they are in a car, he suddenly understands what K-9 is saying and crashes the car through the front doors of the school. He and Kenny rush to the pupils. Lassar shrieks, summoning the other Krillitanes, who transform into their bat-forms. Mickey and Kenny meet up with the others and run into the cafeteria, pursued by the bat creatures. Lassar tells them he wants the Doctor alive, but to eat the others.
As the Krillitanes attack, a laser shoots one of them down. K9 appears in the doorway, blaster at the ready. The Doctor tells K9 to hold them off while they retreat. However, K9’s battery is failing and Lassar tells the Krillitanes to ignore “the shooty dog thing” and get the others. In the physics lab, the Doctor realizes the solution is the oil. The Krillitanes have changed their physiology so often that even their own oil is toxic to them now. The Krillitanes start bashing down the door. The Doctor tells Mickey to get the children unplugged and evacuated. Kenny triggers the fire alarm, the high-pitched sound hurting the bat-like ears of the Krillitanes and stunning them long enough to get past to the kitchens. However, this doesn’t work for long. Lassar simply punches through the wall and rips out the power lead to the alarm.
Mickey unplugs the computers and gets the children out of the school. In the kitchens, the Doctor finds the barrels of oil are deadlock sealed. He gets the others out. He and K9 stay behind. K9 tells the Doctor that the barrels will not withstand a direct hit from its laser, but as its batteries are weak, it has to remain. The Doctor protests, knowing that K9 will be caught in the explosion, but the dog replies there is no alternative. Sadly, the Doctor bids his old friend good-bye, calls it a good dog and exits the building. The Doctor takes Sarah’s hand and while she asks about K9, drags her away from the school.
Brother Lassar and his brethren enter the kitchen in human form, searching for the Doctor. Lassar mocks K9 when he sees him, but K9 shoots a barrel, spilling the toxic oil over the aliens. Lassar snarls to K9, “You bad dog”; the dog replies, “Affirmative.” The explosion takes out a large chunk of the school. The pupils cheer the school’s destruction, and hail Kenny as the hero who did it. Sarah weeps over K9’s sacrifice as the Doctor comforts her.
Later, Sarah enters the TARDIS in a park. The Doctor suggests that Sarah join them, but Sarah declines, saying it is time she found a life of her own. Mickey asks if he may join them in the TARDIS. Sarah says they need a Smith aboard the TARDIS, and the Doctor agrees, although Rose does not look pleased.
Before she goes, Sarah admits that she wants to stay. When Rose asks her what to do, she reassures her that some things are worth getting your heart broken for. She adds that someday, if Rose needs to, she should find her. Outside, Sarah thanks the Doctor for her time with him. The Doctor asks if there has been anyone special. Sarah tells him that there was one man whom she traveled with for a while, but he was a tough act to follow. She asks him to say good-bye this time — and he complies, saying, “Goodbye…my Sarah Jane!” He smiles at her and they hug tightly, with Sarah Jane looking to be on the verge of tears. Sarah then watches the TARDIS disappear, but as it does so, a brand new K9 is revealed. K9 explains that the Doctor rebuilt and improved it. Happily, Sarah orders K9 home. They have work to do…