The Doctor understands that Benny is upset about Guy de Carnac’s death, but he can’t connect with her grief on a human level. Determined to explore the human condition and better understand his friends, he travels to an interplanetary flea market and contacts a genesmith named Laylock. Using a fictional persona designed in the TARDIS data banks, Laylock programmes a set of nanites to transform the Doctor into a human and store his Time Lord biodata in a pod the size and shape of a cricket ball. Following the Doctor’s hurried instructions before he collapses, Benny pilots the TARDIS to the English village of Farringham in 1914, where “John Smith” will live as an ordinary human for three months. Since the biodata pod would adversely affect the TARDIS if left inside, Benny hides it inside a tree which grows around the pod, enclosing it. She then takes a room in a house owned by local rake Alexander Shuttleworth, and gets to know the townspeople, including a young suffragette named Constance. Meanwhile, Smith takes a position teaching history at Hulton Academy and befriends his fellow teacher Joan Redfern. One of his students, Timothy Dean, is frequently bullied by his fellow students; he thinks he’s found a friend in the odd new history teacher, until Smith, unable to understand why his own instincts seem to disagree with the world, advises Dean to lay low and try to fit in. The Headmaster, Rocastle, is pleased; at last Smith is starting to understand how things are done at Hulton.
Nine weeks pass without incident, before the alien Aubertides arrive. Laylock is one of this shape-shifting family, who can transform into the shape of any creature they consume -- and who want the biodata of a Time Lord. Greeneye contacts Benny, pretending to be the Tenth Doctor in order to find out where she has hidden the pod. She sees through him, however, and while trying to escape she accidentally wounds the Aubertide child Aphasia. Aphasia is taken to the hospital, where she releases a corrosive gas which kills everyone else, and eats a nurse in order to heal herself. Benny, meanwhile, contacts Smith to warn him of the danger, but he doesn’t believe her claim that he is really an alien lord of Time -- especially when she finds that the biodata pod is missing. The pod has fallen into the hands of Timothy Dean, and as data leaks from it he is beginning to take on the physical and mental characteristics of a Time Lord. That very night, the school bully Hutchinson accidentally kills Dean while “pretending” to hang him in a mock trial, but Dean has acquired a respiratory bypass system, and he returns to life.
Joan invites Smith to her home for dinner, and they finally acknowledge that they are in love. Truly happy with his lot, Smith returns home to work on a children’s story, about an inventor who travels to a distant world in his time machine and teaches its people about laws and love; but the people of Gallifrey take his ideas too much to heart and become boring and stagnant, until he is forced to flee from them in order to be free again. As he writes, Smith is attacked by the Aubertide Serif, who eats only his little finger and is thus able to access his memories without being overwhelmed by the nanites which have made him human. Serif tries to force Smith to remember the things which he has forgotten, but Joan arrives to return the gloves which Smith had forgotten at her home, catches Serif by surprise and knocks him out with a vase. Serif is taken to the police station, where the police call in the army to investigate the mysterious attacks on Smith and Benny and the horrific deaths at the hospital. Smith, recovering from the attack, proposes to Joan and gives her an engagement ring with a large jewel in the centre; however, he is unable to remember where he originally acquired it.
Constance contacts Benny, offering her help, and shows her a cache of explosives stored by suffragettes under a local statue. The explosives are too sweaty and old to be safe, however, and Benny goes to Alexander for help instead. She is forced to explain where she’s really from and what the attackers are after, and shows him her personal datapad to prove her extraordinary claim. Unfortunately, she’s so exhausted and he’s so excited that she unthinkingly leaves the pad with him while she sleeps -- and when she awakens the next morning, she finds that he’s learned his dear friend Richard Hadleman will be killed by mustard gas in the forthcoming war. The Aubertides then attack the house, but Constance leads Benny and Alexander to safety. When she asks Benny why they’re under attack, Benny explains about the pod, but admits that she doesn’t have it and doesn’t know where it is. Constance then takes Benny and Alexander prisoner, revealing herself to be Greeneye -- the real Constance has been captured and eaten.
Greeneye and August rescue Serif from the police, and in the process they discover that armed forces are on their way. In order to avoid a battle which would attract the attention of the Time Lords, they set up a double Time barrier around the town, preventing anybody from getting in or out until their mission is complete. The captive Alexander and Benny are held in the Aubertides’ base, an invisible dome in the forest, where August, the head of the family, explains that they intend to use the biodata in the pod to give themselves the power to regenerate. An ordinary Aubertide family buds to a maximum of eight members, but with the power of regeneration, each member of their family will be able to regenerate twelve times and bud an additional family member from each new body. Each of the new family members will also be capable of regeneration, and soon they will be able to conquer Gallifrey through sheer force of numbers.
Dean, having come to terms with his new abilities, wanders onto the field during OTC training while Rocastle is demonstrating the use of the Vickers machine gun. Unwilling to admit how terrified he was, Rocastle tries to beat some sense into Dean, but Dean knocks him out with the touch of a finger, knowing that in a few short years Rocastle will die of a painful bowel tumour. He enters the forest to contemplate his new life, but is spotted and pursued by the Aubertides; they lose him, but now know that the pod is held by a boy from the local school. Meanwhile, Benny and Alexander escape from the dome, and they also spot but lose Tim in the forest. They go to the school, where Alexander claims that a boy has stolen a valuable pottery sphere from his museum. Rocastle assembles all of the boys and their masters in the Hall to demand that the miscreant confess, but the Aubertides arrive, surround the school and give the occupants thirty minutes to hand over the pod.
Rocastle, who has been seeking a cause for years, organises the students to fight the attackers, despite Benny’s objections that they’re only boys and will be slaughtered. Smith’s House is placed in charge of the Vickers gun, but when one of the boys, Phipps, tries shooting at the Aubertides, they return fire and kill him. Smith finds that he is unable to fire back at them in anger; although Benny and Joan may disagree on whether he’s John Smith or the Doctor, they both agree that that’s just not the sort of thing he does. Smith tells the other boys to drop their weapons, and deduces from the Latin inscription on the library walls -- the school motto, which translates roughly to “bigger on the inside than the outside” -- that there is a secret passage between the library of Hulton Academy, which was once a country home, and the local tavern.
The deadline expires and the Aubertides storm the school, killing everyone who gets in their way. Aphasia is killed in the fighting, and the enraged Aubertides take shelter under a force field and detonate a fusion bomb which transforms the school and every student within into glass. Fortunately, the bursar Mr Moffatt has already evacuated a number of boys through the tunnel, which he has been using for some time to visit the tavern after curfew. Rocastle, Hutchinson and a few other boys also reach shelter and survive, and Benny finds Rocastle wandering the remains of the school in shock. Hutchinson, however, seems convinced that this was a glorious battle, and intends to continue fighting.
Smith, Joan and the boys of his House split up to search for Dean and the pod. As Smith and Joan search together, Smith finds his memories changing, depending upon which way he turns his head. Joan realises that he’s picking up memories from the pod; everything Benny has said is true. They find Dean, who has finally convinced himself that the pod is not meant for him, but Smith announces that he intends to hand the pod over the Aubertides so they’ll leave him alone and he can marry Joan in peace. Dean refuses to allow this, and flees with the pod as the Aubertides show up. The aliens take Joan hostage, threatening to kill her if Smith doesn’t hand over the pod by dawn.
Dean finds a police box hidden in the woods, and follows the instructions whispered to him through the telephone in its cubby. Alexander’s friend Richard has returned, and Dean uses his new time-sensitivity to lead him through the time barrier so he can lead Smith to Dean. Dean uses the powers of the time barrier to show Smith a potential future, in which the Aubertides have conquered Gallifrey and launched a reign of butchery across all space and time. Smith reluctantly accepts that he must not surrender the pod to the Aubertides, but how can he defeat them and save Joan? What would the Doctor do?
Benny, Rocastle and the boys see the Aubertides taking Joan to their dome, and Rocastle insists that they rescue her. Benny lures Greeneye and Serif to the old statue, where the boys have built a pit, but only Greeneye falls into it. Serif shoots Rocastle, but Rocastle is deliberately standing above the sweaty explosives, and the explosion kills both him and Serif. The boys nearly beat the helpless Greeneye to death, but Benny stops them; she will not allow anyone to die. Smith arrives, and accompanies Benny to the Aubertide dome, where they pretend to be Greeneye and Serif and try to rescue Joan; however, they fail, and barely escape themselves. Smith is running out of time, but as he wonders what he should do next, he has a vision of his first love, Verity -- who is in fact an aspect of the TARDIS, placed in his mind to protect those parts of the Doctor’s psyche which could not be completely erased from Smith’s mind. He now knows who he really is; whether the Doctor or John Smith, he is never cruel or cowardly, and is a man of peace even in times of war.
At peace, Smith uses the pod to change back into the Doctor, and the Doctor, pretending to be Smith, takes the pod back to the dome and hands it over to August. August, expecting an influx of Time Lord biodata, is unprepared for the human nanites in the pod and is mentally transformed into Smith. The last surviving free Aubertide, Hoff, guns Smith down as he tries to release Joan, but in the confusion the Doctor operates the time barrier controls and traps Hoff, August’s body, and the pod -- which now contains August’s biodata -- between the walls of the time barrier. In the void between the walls, he bids farewell to the late John Smith, and then sets the Aubertides’ equipment to self-destruct. Joan survives due to her engagement ring, which is in fact the ring which the Doctor often wore in his first incarnation.
The Doctor, understanding vaguely that Smith was fond of Joan, sends her home to relax, but Benny orders him to admit the truth to her before leaving. Joan is upset to learn that Smith died for her, but she must accept that, although the Doctor remembers his experiences, he isn’t Smith and can’t go back to being him, not even for her. Joan gives him her cat Wolsey as a memento. Before leaving, the Doctor orders that Greeneye be kept away from meat; however, when the army arrives to arrest him, he convinces his guards to give him a corned beef sandwich, and then transforms into a cow in order to give his guards the slip -- only to be taken to a slaughterhouse. The Doctor and Benny depart, unaware that Smith students Alton was in fact a Time Lord all along, there to keep an eye on things and ensure they didn’t go too far. Rocastle’s death has shown Dean that the future can be changed, and this gives Alexander new hope that Richard -- whom Benny has realised is far more than a friend -- may survive the battle in which he is “destined” to die. In fact he does (although Hutchinson doesn’t), and he and Alexander live to a great old age, as does Dean. Although fully human again, he is never cruel or cowardly, and even in times of war, he is a man of peace. He never bullies his enemies, but outsmarts them. He may not be the Doctor himself, but he has learned from him.
Source: Cameron Dixon