The TARDIS materialises in a beautiful rainforest overlooking a huge lake. The Doctor and Nyssa emerge to see enormous shrubs and plants reaching high into the sky. Everything seems gigantic; Nyssa believes she's seen fishing boats that are smaller than some of the leaves here. She considers sailing on the lake using one of the leaves as a raft, but the Doctor says they're not here for fun. He produces some harnesses and Nyssa worries that he's expecting them both to swing through the trees. She's not exactly scared of heights, although she thought he might be after he fell off the telescope on Earth. He points out that if he'd been wearing a harness at the time, he'd still be handing out jelly babies in a mile-long scarf. Remembering his regeneration, she wonders whether he can ever die, and he assures her he can, which is why he wants them to use the equipment from a rucksack he borrowed from Mallory and Irvine just before their final attempt on Everest in 1924. He remembers telling the explorers that if they lost their gloves on the mountain, they'd lose their lives as well. He never saw them again, and Nyssa wonders if that might have something to do with the fact that he still has Mallory's gloves, which he presumably failed to return!

The Doctor tells Nyssa that the Time Lords describe this planet as a dreadful place, which shows how much they know. She wonders why they keep asking him to make trips for them if they disapprove of his lifestyle so much. The Doctor thinks they're trying to be clever by asking him to go to places he'd give anything to see, knowing that if he refused to go they'd send a bureaucrat instead who wouldn't appreciate it properly. She asks what they're going to be dealing with on this mission; is it an alien invasion or a mad scientist? He tells her it's actually a fellow Time Lord. Cardinal Zero was well on his way to getting a seat on the High Council when he suddenly decided he'd had enough and went to live in the trees instead. The Doctor's job is to talk him down and persuade him to go home before he damages the time stream. Nyssa isn't surprised Zero wants to stay here, as it's so peaceful -- but then suddenly they hear strange voices crying out as if in a struggle. The Doctor wants to see what all the noise is about, but that will mean climbing up into the huge trees...

Two man-sized bird people, Redklaw and Hoodeye, are engaged in a fight over some food. Both birds accuse the other of theft, but the argument soon descends into a disagreement over which of them has received the most injuries. Redklaw brags that he nearly broke Hoodeye's arm and warns his opponent to leave before he suffers even more. Not far away, the Doctor and Nyssa observe the two creatures and try to work out what's going on. As they move closer, an elderly bird-woman arrives with some guards and orders the two men to be restrained. Redklaw immediately grovels before the woman, Carrion, who he addresses as one of the elders, and begs for forgiveness. Carrion demands silence and then finds both of the men guilty of committing violence against each other. Despite repeated warnings in the past, they've continued their feud and will now be judged according to the Songs of the Avian People. She orders her yeoman to bring over the two men's younger siblings. Carrion reminds Redklaw and Hoodeye that it's been a long time since she was forced to injure innocents as young as these two. Both fighters ask to be punished instead of the children and offer themselves in exchange, but Carrion will not listen to their arguments. She points out that their actions have degraded their race and if they have no stomach for violence then they shouldn't have started the fight. She orders three talon cuts to be given to Hoodeye's sibling and an injured arm to be given to Redklaw's sibling. The chicks scream out in agony...

Nyssa races over and calls for them to stop what they're doing. Carrion tells her to step forward, assuring her she has nothing to fear from the flock. Nyssa is upset to see the chicks are bleeding, but Carrion explains that all must be responsible for the actions of the nest, and by their law, the most dearly beloved of their race is punished in place of the wrongdoer. The Doctor steps forward and apologises for the interruption, explaining that his companion's concern was for the children, but Carrion says their form of justice has served them well since the hatching of the world, allowing nest after nest to live in peace. The two wrongdoers will not be able to look the children in the eye, which means they're unlikely to fall into violence again so soon. One of the chicks speaks up in Carrion's defence and says they don't blame her for what's happened as it was their brothers' fault for fighting. Nyssa believes this is unacceptable in a civilised society, but Carrion knows that other worlds live in chaos and destruction. She rebukes Nyssa for considering herself more superior, especially given the company she keeps. They realise she's making a criticism of the Doctor, but they're still surprised when Carrion welcomes him by name and says they've been expecting his arrival for some time!

The Avian Parliament is to reconvene shortly, which means there is just one more day to go before the murderer among their people is judged. The young bird-woman Snowfire approaches her brother Hoodeye and asks if it's true that he's been caught fighting again. He admits that he's shamed the family but blames Redklaw for stealing food from them. Snowfire wonders if all the men in their family are insane. Their father has been arrested and is due to face trial tomorrow, and if he's found guilty, the punishment will be handed out to his most beloved. Hoodeye offers to meet with the Lord Saja and say he is their father's favourite, but since his own arrest, their father has publicly disowned him, so the punishment will now go to Snowfire.

The crowds make way for the return of Lady Carrion and her honoured guests, the strangers from another world. The Doctor and Nyssa are overcome with the fantastic view of the town, which is located hundreds of feet up in the trees and appears, at first glance, to be floating in the air. The Doctor asks Carrion how long it's been since their people lost the power of flight; it was so long ago they can no longer remember, but life in the trees suits them well. Some of the walkways are at least 200 feet high and the Doctor thinks they must have been built very carefully; knowing the laws on this planet, if one of the builders caused someone else's death they'd probably throw his family down after the victims. Nyssa tries to persuade the Doctor that the rules here are uncivilised and he agrees. Carrion points to their meeting place, the Parliament of Birds, which is just below them and which is also the home of their ruler. Carrion suspects Nyssa thinks his nest should be more like her own home, the TARDIS, but the Doctor merely expresses surprise that they allow themselves to be ruled by an alien. Carrion explains that Zero proved himself on their terms and has followed their laws to the letter, earning his position through hard work and trust. There was no Time Lord trickery, and at their leader's own command, his TARDIS was floated out on a bed of moss and sunk to the bottom of the great lake. He told the Avians that he came from a world ruled by arguing men with big collars who consider themselves to be gods, and he warned that sooner or later his people would send the Doctor to find him. The Doctor thinks this world looks very much like Traken, but Nyssa believes the rules here are random and brutal. She wonders if Cardinal Zero is planning to soften the laws or make this place more like his own planet. She's surprised that the Doctor isn't happier that another Time Lord has left to see the Universe for himself, but the Doctor points out that Zero is a Prydonian, one of the Council of the Great Mother, which specialises in the politics of regeneration. If Zero came from any other chapter, the Doctor wouldn't worry so much, but Prydonians are cunning and you can't take your eyes off them for a second. He's embarrassed when Nyssa reminds him that he's a Prydonian himself.

Carrion returns and says that the leader is ready to see them. Before the Doctor can approach the throne, he's ordered to show respect by lowering his head and spreading his arms in a winged fashion. The Doctor would much rather just pop his head round for a quick chat, but Nyssa reminds him that he needs to show respect to the office, not the person. He is greeted by Zero, who was half expecting an assassin to be sent. He regards the Doctor as a token rebel, tolerated by the Council to maintain the illusion of a free society. The Doctor reveals that Temporal Projectionists on Gallifrey have predicted that this species will make the jump from steam to orbital space flight in less than three generations. Ten years ago, this world consisted of a series of feudal baronies, but the Avians have taken to democratic governance extremely quickly. Zero adds that they'll have the power of flight back very soon, once they've worked out how to get helium for their balloons. He says their whole culture is based on flight and it's a longing he's happy for them to re-discover. The Doctor asks why he's playing god with the Avians, but Zero denies this and says that the bird-people speak of a prophet who will one day lead them back to the sky. If he just wanted to be their saviour, he could have just used a pair of anti-gravity boots from his TARDIS and float around giving them directions.

This prompts the Doctor to point out that Zero's TARDIS is actually the great lake itself in disguise. Nyssa is surprised and wonders why he didn't just send his TARDIS back, but the Doctor realises he still needs it to speak the Avian language, as he lacks a syrinx, the vocal organ of a bird, and his larynx is incapable of making bird tones. Zero adds that the Avians communicate through more than just song; they also rely on ritual display, plumage and dance, which is why he's dressed in feathers. The Doctor explains that in the legends of Earth, Syrinx was a water nymph of great beauty who was courted by Pan, a half-man/half-animal demigod, but rather than welcome his embraces she ran to the lake and turned herself into a bed of reeds. Pan then cut down the reeds and fashioned himself a set of pipes with a delicate wistful tone -- and pan pipes have ruined every hotel lobby from then onwards. Zero says the lake below them is very different from the ones in Greece, but he still thinks of Syrinx whenever he looks down on it. She was physically transformed through her rejection of the baser instincts -- a form of regeneration, if you like. The Doctor points out that if Zero regenerated here, the Avians would no longer recognise him, and Zero accepts that if he were to change, it would interfere with the Avians' visual language to the point where they could never accept him even if they could understand the reasons intellectually.

The yeoman reports to Lady Carrion that the prisoner has been escorted across the lake. His next-of-kin have been informed and are being kept under close observation before being escorted alongside their leader when he makes his journey tomorrow. Carrion is pleased and says they don't want anyone fleeing the coop this time. She orders the yeoman to make sure the tool of execution is kept safe...

Zero takes the Doctor and Nyssa to see the hatcheries. The bows of the trees hold the nests, which give shelter for the shoots; the trees grow creepers to keep them safe while the droppings of the chicks combine with the fruit juices to make a contact poison called the Yoke of Darts, which deters males and stops them smashing the eggs. It's a perfect example of symbiosis -- the chicks are protected, the fruit grows uneaten and any males that are killed will turn into compost. The poison itself is harmless to females and chicks, but Nyssa wonders whether it would kill Time Lords. Zero says it wouldn't, but only in the same way that a hail of bullets wouldn't kill them. Although perfectly painless, it would still be traumatic enough to trigger a regeneration. He invites Nyssa to pick some up. She thinks it looks and smells beautiful and asks if she can keep it, and the Doctor tells her to place it in the rucksack for safety. Zero then points to a great city in the distance called Platch, which he'll show them in the morning. The path leads behind the waterfall that feeds the lake, so he tells them they'll need waterproof clothes from their TARDIS, which should be with them before dawn and will be left in the clearing below where it'll be quite safe. Zero needs to visit the city to act as judge and jury in a murder trial, the first one in six years. He is to hear the accusation, listen to the defence and then make a decision on the spot. The person most beloved of the murderer will then meet the same fate as the victim, which means he or she will be beaten to death with a lump of granite. The Doctor is horrified that Zero would knowingly kill an innocent person with his bare hands, but Zero reminds him this is the Avian culture, not his. He asks whether they think he should interfere and the Doctor says perhaps, but Nyssa says most definitely yes. Zero points out that one minute he's being accused of doing too much, the next of doing too little. He wonders what the Time Lords have asked the Doctor to do here, and the Doctor replies that the High Council trusts him to follow his own instincts. Zero laughs and then offers to show them both to their bowers as they have a busy day ahead of them and will need to rest. He'll have some food sent up, but he advises them not to eat anything blue -- there's no exact equivalent to it in our culture, but the nearest comparison he can make is 'road kill'.

Hoodeye urges his sister Snowfire to come back and rethink what she's planning. He argues that the new arrivals are strangers, aliens, and anything could happen. She counters this by asking him when he last thought about anything. Meanwhile, in his bower at the top of the trees, the Doctor is struggling to get to sleep and thinks his nest must be lined with holly. He hears a noise outside and assumes it's Nyssa having trouble sleeping too, but the face that greets him is Snowfire's. She asks for his forgiveness and explains that her father, Willowsap, hasn't been himself since her mother died; he recently fell into a dispute over fruit trees near their nest, and in one of his black moods, he killed the neighbour in full view of the whole flock. Tomorrow, the Saja is due to hear the case against her father and he will be found guilty, and according to the justice system on this world, she will be put to death in his place. She tells him that many people are now saying the innocent shouldn't be punished for the crimes of the guilty, but no one is allowed to openly question the law here until the curse of their biology is lifted and they are able to return to the skies. The Doctor realises that Cardinal Zero is committed to non-interference and therefore isn't permitted to change the law himself. Snowfire asks the Doctor to help her, but she can't flee as the punishment for escaping justice by leaving or committing suicide is for her whole flock to suffer her fate. The Doctor tells her that he is not without influence here and asks her to go home and wait.

Once she's left, the Doctor wakes Nyssa and tells her that he needs her rucksack. There's no point her trying to go back to sleep now as dawn is nearly here and the dawn chorus on this planet is likely to be overpowering. She hands him the rucksack and notices that the poison plant has disappeared, but the Doctor is too busy to listen. He searches the contents and finds some rope, but notices that the gloves he borrowed from Mallory have gone too. Nyssa wonders what he's up to and regrets pushing him into action. The coast is clear, so the Doctor tells her to go back to the TARDIS, tie the rope over the walkway and then put the harness on. He tells her of a Gallifreyan protocol which dictates that before a period of exile a Time Lord is required to regenerate. Zero will know this and Nyssa wonders whether this means the Doctor is going to 'kill' him. They approach Zero's nest and hear him sleeping inside. They're surprised to find the area unguarded, but the Doctor assumes no one would ever dare hurt him. Nyssa leaves for the TARDIS and the Doctor tries to wake Zero up. When his first attempt fails, he shouts out a warning about Vampires in the Capitol -- and the Cardinal leaps to his feet. Before the Doctor can speak to him, Zero appears alarmed to discover the Yoke of Darts has been placed on his bed. The Doctor notices that the missing gloves are here, and Zero concludes that someone used them to carry the poisonous plant into his nest. Suddenly the Cardinal grabs the plant and deliberately infects himself, then shouts out at the top of his voice that the Doctor has killed him! The Doctor realises straight away that he's been set up. Slowly Zero starts to weaken, and then Nyssa returns with Lady Carrion who demands to know what's happening. Zero is in no pain, but he makes an exaggerated attempt to thrash around, as if in agony. Then he runs over to the balcony and falls over, dropping into the lake far below. Nyssa insists that they try to get him out, but the Doctor reminds her that he's simply returned to his own TARDIS.

Carrion accuses the Doctor of killing their leader and orders the guards to arrest him, but moments later, the bird-like form of Zero appears before them all, flying in mid-air hundreds of feet above ground level. Carrion immediately recognises him as their prophet, and the Doctor realises the poison must have been more complicated than he thought. It's altered the Gallifreyan DNA and turned Zero into something half-Time Lord and half-Avian. The Doctor is impressed by Zero's wings, and the Cardinal agrees that it looks like he won't be needing the anti-gravity boots after all. Nyssa is struggling to keep up with what's happened and Carrion demands to know where their leader is. Still adopting the guise of their prophet, Zero surprises everyone by announcing that he killed their leader by drowning him in the lake. Carrion is stumped as the prophet has no kin or flock that can be punished in his place. Zero agrees that he has no family here, although he suggests they might try asking his cousin, the Doctor...

Molly Richards arrives at the Tower of London and is ordered to identify herself by the guard Bert. She claims to be the King of Spain, and the guard laughs and apologises for not recognising her in the dark. She asks after her husband, the royal jailer, and learns that he's busy taking on some new prisoners. The guard tells her that they didn't arrive by boat at Traitors' Gate in the usual way but were brought in through the main gate under special guard. He lets Molly through as she's carrying her husband's supper. Inside, she listens to her husband's complaints about the July heat wave, then he tells her about the strange prisoners who arrived today...

In the dungeons, the Doctor and Nyssa can't believe they've been arrested for forgery! The Doctor is particularly angry and believes their captor, a man he still admires for his brilliance, is nevertheless awkward, spectacularly rude and a homicidal maniac. The Doctor blames himself -- if he hadn't been so occupied by a man at the next table he wouldn't have given Nyssa coins from the wrong era and they wouldn't have been arrested. Nyssa wonders what was so fascinating at the next table and he tells her it was a demonstration of alchemy. Gobbledegook mainly, but there were interesting parallels with quantum light-wave particle duality. The Doctor's main mistake was being so stupid as to not realise he was actually talking to Sir Isaac Newton, director of the Royal Mint. At that moment, Sir Isaac himself arrives in the cell and the guard offers to remove their manacles if they answer all his questions. Before they can respond, Sir Isaac demonstrates his authority by firing a pistol into the bed and then threatening to put the next bullet in Nyssa's head. He's now had a chance to examine the Doctor's coins in more detail, but they're not a form of currency he's aware of and wonders if they were intended for someone's amusement. Whatever the answer, he says the Doctor and Nyssa will hang for it and warns that he doesn't like fools, forgers or Catholics.

The jailer finishes his meal and congratulates his wife. They joke about setting their unruly children on Sir Isaac, but then they hear the sound of the gun shot and the jailer rushes to the cell where the guard is waiting outside. They're both familiar with Sir Isaac's technique of terrorising the prisoners, so the jailer decides to hang around in case it brings on another of Sir Isaac's funny turns.

Sir Isaac tries to work out who his prisoners are and reminds the Doctor that he earlier exposed himself as an alchemist. He asks the Doctor who sent him, but the Doctor insists he had no idea who he was dealing with at the time as Sir Isaac was disguised as an Algerian juggler with a false chin. The Doctor implies that they've met before, but Sir Isaac is sure he'd remember if this was true. Nyssa covers by claiming that the Doctor pointed Sir Isaac out to her a long time ago, which makes Sir Isaac think they were probably looking down the barrel of a musket. He tells his prisoners that forgers are normally drawn and quartered, but curiosity has got the better of him. One of the Doctor's coins is an obvious antique, yet the others are made from a metal he's never seen before. The Doctor claims he just picked it up on one of his travels. Sir Isaac talks about his boredom with Parliament and admits that in all his years there, he only ever spoke once, and that was just to ask for the window to be closed as it was causing a draught. He returns his attention to the coins and demands the Doctor give him answers or he will rip the truth from him with pliers.

Sir Isaac leaves, promising to return later, and asks the jailer not to spit in the prisoners' food unless he expressly commands it. He observed Molly arrive earlier with the jailer's dinner and orders him to give it to the prisoners to save time. He also asks him to check the food for poison first as the prisoners are valuable to him and if they die he will drown the jailer's children like a sackful of kittens. Finally, he warns that if anyone interrupts him without good reason, their toenails will be torn out and fed to the ravens.

The Doctor tries to remember whether any of the seven coins in the bag had legs, and when Nyssa tells him they didn't, he concludes that they're probably all of Earth origin. He tries to reassure Nyssa that things could be a lot worse (a Dalek taskforce, Mars winning the Ashes again, that sort of thing) but they can rule out any hope of secret passages or unexpected help from outside, and he really must get round to making a new sonic screwdriver. Their only hope is to tell Sir Isaac the truth, as he is known to value that more than anything, and hope that his religious beliefs will force him to let them free. He traditionally wakes up with worry at four every morning, so they have only three hours in which to escape. The jailer arrives with his dinner and threatens them with extreme violence unless they show gratitude. The jailer sees in the Doctor's face that he's accustomed to being locked up and asks out of professional curiosity why he seems so disappointed. Unfortunately a bell rings before the Doctor can answer, so the jailer leaves. The jailer is informed that Sir Isaac has changed his mind and he now wants the prisoners out in the yard at once, so the jailer thinks he might have just enough time to save his supper. He returns to the cell and tells the Doctor and Nyssa that he forgot to check the food for poison, but before he can eat it, he's informed by the guard that Sir Isaac gave orders for him to escort the prisoners personally.

The jailer takes the Doctor and Nyssa to meet Sir Isaac at Tower Hill, where prisoners are traditionally beheaded. Fortunately execution is usually a spectator sport, so the lack of an audience suggests that's not what they have in mind. Sir Isaac orders the guards to withdraw as the following conversation is not for their ears. Once they're alone, Sir Isaac reveals that he's changed his mind about the metals and is confident that whatever secrets they hold will speak to him later in his crucible. He's more interested in something that was found outside the inn where the Doctor and Nyssa were arrested. The TARDIS is wheeled into the courtyard and the Doctor offers to open it for him, but the guard orders him to stand still or be shot. Sir Isaac has tried to have the blue box burned, scratched and cut, but to no effect, and he suspects it's probably the most interesting item in the whole of London. Sir Isaac had been thinking of a way to ascertain the properties of the coins and has noticed that one of the coins has a map of Europe on one side and a harp on the other, with the year 2003 pressed on it. At first he dismissed it as Irish propaganda as it shows no image of the King (which is laughable as this country's victory over Ireland forever is assured), but then he noticed that the hexagonal coin has a picture of a Queen known as Elizabeth II and is dated 1953. Another coin, valued at two pounds, is made of two different metals. He suspects that if there is a plan to spread Catholic lies, it would make more sense for the fake coin to show Britain being ruled by Spain, but the Doctor assures him once again that the coins are trinkets, made for amusement only, and there's nothing political in them. This makes Sir Isaac even more furious as there's nothing more political in his view than money. He warns that if the Doctor tells any more lies he'll have the girl taken away for "questioning".

Sir Isaac produces another coin from the bag -- a silver one dated 1978 showing a plain man with no crown, a landscape not unlike the Moon as seen through his telescope, and the words 'United States of America'. The Doctor suggests this might be colonial propaganda, but Sir Isaac has concluded that by 1978, an America without a King will conquer the Moon and that by 2003, an Ireland without a King will join up with England's enemies in Europe. The antique coin appears to be Roman, but if this is genuine then perhaps the others are too. Sir Isaac realises they aren't newly minted and have been weathered by use, so they must be old coins from a future that cannot exist. He turns his attention back to the blue box and says he's seen and done things that no other man can imagine. He now believes the box to be a time machine and that the Doctor and Nyssa are time travellers. The Doctor tries to laugh off such a ridiculous suggestion and again offers to show him inside, but Sir Isaac realises that would allow him to escape and go back to smother him when he was still a baby in his crib, or possibly just interfere in his past. He explains that as a young boy he was sold a book on alchemy at a fair and it changed the direction of his life. If the seller was delayed by just one day, he would probably now be just a rector of a dull church somewhere instead of the man he is. Sir Isaac believes that God is everywhere and he intervenes to ensure the Universe stays on its appointed course. He now wonders whether the TARDIS may be a device left by God to help his faithful servants.

Nyssa reminds the Doctor that he said the truth would set them free and he wonders whether they should now tell Sir Isaac the truth, but the Doctor warns this would risk changing history. Sir Isaac suddenly declares that time travel must be impossible -- if they were to go back and kill him while as a child, he would not be able to capture them later, therefore they could not travel back to kill him. Nyssa readily agrees and the Doctor suggests that if time travel was possible then they should be overrun with visitors from the future. Sir Isaac wonders whether there will actually be a future; perhaps the Earth won't survive long enough for time travel to be discovered. He thus concludes that the two prisoners may not be from Earth at all, but from somewhere else... another world where time travel is a reality. He considers quartering them for examination. He raises the subject of the heretic Arius, and the Doctor tells Nyssa that the Arians are a heretical sect whose followers were denounced at the Council of Nicaea in 354 AD. He keeps meaning to go back one day to see for himself... Arius suggested that the Lord Jesus was created by God, not eternally begotten but created, so God the Father and God the Son may not have lived at the same time -- so Sir Isaac wonders if perhaps the same could be said of people who travel through time? Perhaps the same person can even be found in different incarnations? This would make loops of time more pliable as the time traveller may not always be found in the same aspect? He seems to be drawing so many conclusions from just a handful of coins that the Doctor can only say how grateful he is that Nyssa didn't pay by debit card. The Doctor suggests that God would not allow this and eventually Sir Isaac agrees that God balances the celestial bodies and sets them in place, so would not allow such chaos to exist. Then Sir Isaac notices that the Doctor appears to be placing himself in hazard rather than allow these speculations to continue. He examines the last coin, a triangular shape with Oriental-looking pictograms, and concludes that it comes from a time more distant than the others. It's more radical in design and it suggests the powers of Europe will fall to the heathen, but it also shows the solar system on the reverse and the picture consists of fifteen planets, which is far more than humans are currently aware of.

The Doctor is disturbed by Sir Isaac's deliberations and whispers to Nyssa that if anything happens, she's to get inside the TARDIS. Sir Isaac is now considering the possibility that in hundreds of years' time, a cataclysmic war will engulf Europe, and in the middle of that war the Irish will rebel; Britain will be unable to fight on yet another front so it will make terms for peace; America will rebel at some stage and will become so powerful that it will colonise the Moon itself. Yet despite such progress and advancement, something will go wrong -- some catastrophe that will prevent them from unlocking the secrets of time. Nyssa realises that Sir Isaac has become so engrossed in his own thoughts that he's barely even aware of their presence. The Doctor says Sir Isaac was noted for this unique gift -- he could give himself over totally to an idea and abandon everyone around him -- and Nyssa thinks this makes him very similar to the Doctor. Sir Isaac is now considering a natural disaster or invasion, sometime after the reign of Elizabeth II, during which time Earth will be attacked by people from another world and be colonised as easily as Britain colonised India. He turns to accuse the Doctor of coming here to gloat and to view moments of history like a series of trophies. He angrily calls for the guards, who emerge from hiding to grab the Doctor and Nyssa.

The guard mocks the Doctor and Nyssa as he returns them to their cell, but to everyone's surprise they find Molly is already there, looking for the supper bowl she brought to the Tower earlier. She sympathises with the prisoners for suffering at the hands of Sir Isaac and asks Nyssa what her friend does for a living. She's impressed to learn that he's a doctor and recalls that another prisoner they had here last week was a doctor too, but before she can say any more the guard tells her it's time they left for the night. Nyssa is frustrated that they got so close to being back inside the TARDIS. She knows Sir Isaac is mad, but he's also a scientist, so they should be able to reason with him. The Doctor noticed that Molly seemed superstitious, which is not uncommon for people in pre-technological societies, and he decides that as science is getting them nowhere they should look to magic instead. He and Nyssa search the bed frame for the shot from Sir Isaac's gun, then they squash both it and one of Nyssa's earrings beneath the bedpost to form two 'coins'. He explains to Nyssa that he was taught how to perform magic by Harry Houdini and he demonstrates a variation of the French Drop in which he appears to transform the lead 'coin' into a gold one.

The Doctor calls for the jailer and a few moments later, the angry man arrives and demands to know what the problem is. In the arch voice of a stage magician, the Doctor announces that "I cross the void beyond the mind to seek a truth they'll never find -- know me, I am the Doctor!" Then, before the jailer's eyes, he performs the magic trick again and appears to transform lead into gold. He offers the jailer riches beyond measure if he'll let them go free, but the jailer asks to see the trick a second time. He's more interested in the trick than the offer of riches as he has a steady job and a family to feed. Just then, the guard returns and announces that Sir Isaac has changed his mind once more and wants the prisoners brought back into the courtyard yet again.

Back at Tower Hill, Sir Isaac asks the jailer whether the prisoners tried to distract him. He admits that they did and says the Doctor claimed he could turn lead into gold. Sir Isaac knows instantly that it was a conjuring trick and spots Nyssa's missing gold earring. Nyssa tells Sir Isaac that transmutation of base metals into gold is impossible, but there is a state on the quantum level whereby the only explanation for the nature of matter is that certain elements do become something else -- not gold, but elements he hasn't yet discovered. Sir Isaac orders the guards to stand fifty paces away as this conversation is for his ears only. When the three of them are alone, Nyssa decides to tell the whole truth. She explains that she was born on another world and met the Doctor when her home was destroyed. The Doctor himself is an outcast who can walk through time as easily as others can sail the seas. In the future, wars will see whole cities reduced to dust; men will walk on the Moon; Earth will fall to hideous monsters -- but with the Doctor's help, the humans will rally back and drive the aggressors away, not once but many times. The Doctor tells Sir Isaac that he has the greatest respect for his genius and reveals that the greatest telescopes in the future, units of measurement and whole continents on other worlds will be named after him. Sir Isaac begins to struggle to comprehend what he's hearing and becomes increasingly confused, and the jailer realises he's having another one of his "funny turns". The Doctor reminds Sir Isaac of the time the apple fell on his head, but Sir Isaac is still furious about that as his nose bled for three days, so the Doctor apologises for being a fast bowler. The Doctor assures him he'll be remembered for as long as England stands, which Sir Isaac now believes will be until the invasion in the 22nd century. He finally believes everything the Doctor has told him and starts to have a seizure. The Doctor and Nyssa rush to help him, and realise he's swallowed his tongue and will choke to death. The Doctor refuses to take this opportunity to escape to the TARDIS and is determined to save the life of the greatest mind this world will ever seen. The Doctor orders Nyssa to go inside the TARDIS while he stays to aid the increasingly distressed scientist. The jailer arrives and goes to call for help, but as this is likely to entail being smothered in leeches, Sir Isaac refuses the offer. He asks the Doctor for assurance that they'll never meet again, then orders the jailer to let the Doctor go free. He declares that they stand on holy ground, and passes out.

"Something is added to cricket by the angle of the sun as it stands at four o'clock in early September. The shadows are longer, there's a suggestion of colder days approaching, of circular time, of aspects of our lives dying away and returning. The other sort of time is called linear time -- life is hard and then one dies, if that's something one is liable to do. Cricket, to me, seems to stand for the former and against the latter. It's something that dies but returns and writes mortals into history, in stories and statistics. Perhaps that's why it appeals to me. I also die and return, like a hardy perennial. However, linear time is currently impinging on the Hampshire town of Stockbridge in the form of an end-of-season struggle to avoid relegation from the top-most league of village cricket. They're raging against the dying of the light, they need wins not draws. They need umpires to take the brightest possible view of those stormy skies overhead. They need to play in horizontal rain if they have to. I've seen them do just that in the last couple of weeks, but I've joined them so late this year that I may not be much help."

Nyssa watches the Doctor on the cricket pitch and mocks him warmly for the funny pads he's wearing. He offers her a biscuit and asks how her work is going, but she says she doesn't know where to start. He reassures her that writing a novel is a new experience for her, so she shouldn't get too down-hearted about a few false starts, although he doesn't think their guest-house sitting room is the most inspirational place to embark on a literary venture. She wonders if he's suggesting they go somewhere else, but he says he was hoping to stay until the end of the season. She wants to keep trying, but she doesn't really know what she's writing about and every time she thinks about giving up she feels sad. As the Doctor once said to P G Wodehouse, that means there's obviously a story there trying to get out. Unfortunately the cricket match isn't going very well either, and the Doctor realises that it's time he showed some serious aggression.

Back at the guest-house, Nyssa is approached by the waiter who asks her what her book is about. He tells her they've never had a writer staying here before, but they'd better not tell the boss or she'll want to put Nyssa's photo on the wall. The waiter suddenly realises he's interrupted her creative process and he apologises. She calls him back and he introduces himself as Andrew. She tells him she's writing a novel about a world where everyone is very kind to each other and is ruled by a good king. He thinks it sounds a bit dull and suggests she puts a serpent in the garden. He observes that she hasn't got very far considering she's been staying here for over three weeks, and she admits that she keeps re-writing. He asks if it's going to be like Lord of the Rings, but she tells him it's not a fantasy, despite what it might sound like. She asks him to leave as she wants to get back to her work.

The Stockbridge team are impressed with the Doctor's performance, but when Jack suggests getting the county scout down to see him, he explains that he won't be staying beyond the end of the season. Jack is surprised to hear that the Doctor isn't from around this part of the world, especially since the club house has photographs of his family going back years. The team captain, Don, is an ex-pro who moved to the area last year. He knows the Doctor spends the winters away; when he first joined he heard about this wonder player who just turned up one Sunday and asked if he could play with them. The Doctor says he's also heard about Don's impressive record with Lancashire. Don has been trying to whip the team into shape, but they're a useless lot and he's holding them up on his own. The Doctor argues that they're not in such a bad state really, and even if they get relegated, there are some promising youngsters in the junior team that'll take them back up again. Don refuses to accept that the team will go down and says the whole country has gone mad about cricket since England won the Ashes.

The next day, Andrew notices that Nyssa has written more pages, and tentatively asks if there's still no villain. Nyssa can't understand why there should be a need for one, but he explains that in order to have drama you need to have some conflict. Nyssa doesn't want conflict and in any case the book isn't for publication. In fact, it's quite likely that nobody else will ever see it. He asks her what the point is, but she is abrupt with him and again she asks him to leave her alone. Andrew thinks it's pointless sitting here all day if she's not even going to show it to anyone. As she gets up to return to her room, he offers to read it himself, but she doesn't think he would understand it. He assumes she means it will be too intellectual for him, and he assures her he's a grad student and is only a waiter while he's waiting for the right engineering job to come along. She tells him the book is very personal and reminds him once again that it's not a fantasy novel, but she has no wish to show it to him now as he'll only laugh at it. He asks her where's she's from, as she doesn't sound British, and when she tells him she's from Traken he claims his sister had a boyfriend from round there. She knows he's lying but even though they exchange a few insults, Andrew notices she's smiling. He invites her to a cricket club ball in a couple of weeks and says that'll give him time to read her book.

Later, the Doctor tells Nyssa the ball is a charity event on the last night of the cricket season. It's a grand buffet dinner at the Stag's Head Hotel to raise funds and to hand out awards for the best performances of the series, followed by dancing until late. Nyssa asks if he's intending to go, but he says he usually tries to get away straight after the last match as it makes it difficult for them to give him any awards. She pretends that she's pleased, but he realises she wanted to attend and tells her there are some very nice formal dresses in the TARDIS wardrobe and he's quite prepared to put on a dinner jacket if she wants.

The Doctor congratulates Don on arranging for the mid-week nets to be put up again to aid with the training. There are only three games left and they're going to have to win them all in order to stay safe. The Doctor practices his bowling and nearly takes Don's head off, which is exactly the sort of performance Don wants to see. The Doctor hopes he didn't embarrass Don earlier by mentioning his career as he got the impression he preferred to remain modest. They talk about his coaching career and Don admits he was never quite good enough to get into the first team as he was a late bloomer, so he moved before it was too late and made sure he kept his fitness levels up. He eventually got into the first team for Warwickshire, but then a South African lad turned up and Don got sent back to coaching. Now that he's retired he's been looking for a coaching job, so he moved down here to explore some possibilities. That didn't happen either so at the age of 38 he walked into a Job Centre and ended up working in the local betting shop.

Nyssa is taking a shower in her hotel room when there's a knock on the door. She thinks it's the Doctor, but it's Andrew inviting her to join him on his day off. She tells him she needs to work, but she's intrigued when he says he's going to Traken. It's only about 40 minutes away and there's a pub there with a four-star restaurant, and he was wondering if she wanted to show him around her home. Later, Andrew pulls the car over and announces they've arrived at Traken Village, which is twinned with somewhere in Germany that he can't pronounce. Nyssa admits that this isn't the Traken she came from and he wonders why she let him drive her all the way here, but she says she was curious and wanted to see the place. She thought there might be something special or even frightening about it, but it's really quite ordinary. Andrew thinks she's a bit odd, but at least they can still go to the restaurant.

The Doctor returns to the cricket club and finds the team discussing tactics for tomorrow's match. He orders a lemonade, but Jack insists he has a pint of beer and then he makes some unpleasant derogatory remarks about the Estonian club barman Anton. He claims Anton was brought here by a pikey and is paid in bottle caps, but then he's surprised to find that the Doctor can speak to Anton in his own language. Don takes the Doctor to one side and advises him that drinking lemonade is very bad for team building and he should be drinking beer with the rest of them. When Don says the Doctor's either with them or he's not, the Doctor challenges him to reveal what tactics they've come up with in the hours they've been here...

As they leave the restaurant, Andrew offers Nyssa his coat as it's starting to get cold, but she says she's had too much wine to feel the cold. He's noticed that she gets talkative when she gets drunk, but Nyssa says she isn't drunk and all she's doing is asking him lots of questions. She knows now, for example, that he helps out in a foster care home, but he points out that he still doesn't know anything about her. She asks him if he really wants to see her home and she points up to the night sky, to a star close to the Orion Nebula. The light of her home planet's destruction is still making its way here and you can see it even with a small telescope. Although her world was destroyed, the time it takes for the light to get here means she can still point to the place where everyone she grew up with lives. Everyone except one person, who is lost to her. As the truth slowly dawns on Andrew that she's no longer claiming to be a fairy princess but an alien, Nyssa notices the change in his voice. He tells her he believes her story, but she knows he's just saying that because he's become interested in her, albeit in a rather awful way. He asks her to appreciate how stupid her story sounds, but she tells him that there's no point continuing this conversation anyway as she'll be leaving soon. He starts getting angry and thinks she's making an excuse -- but then he decides to take a gamble and kisses her. He promises to stop if she tells him to, but she doesn't and admits this is the first time she's ever done that. She often thought about this moment and assumed it would be an obvious development, like a step in a series of steps, but now the moment has come she's still surprised. She notices how he's become completely vulnerable and she likes that. Letting surprises in is a new skill for her, as indeed is kissing. She knows she needs some practice, so she invites him to continue if he wants...

The next day, the cricket match has been a success and the Stockbridge team congratulate themselves. They still have two matches to go, but they all performed well and are confident they won't be relegated. The Doctor spots Nyssa in the crowd and excuses himself to go and talk to her. He realises he's barely seen her in the last few days and asks her how her work is going. She tells him she's been inspired and her novel has turned itself into an enormous pile of paper, but she still doesn't have a villain. The Doctor is surprised that she wants a villain and asks whose idea that was, but she becomes defensive. They both become a bit snappy with each other and the Doctor decides to start the conversation again. Nyssa asks him what he thinks of her hair and her dress and he notices for the first time how well she seems to be fitting in to this era. She hadn't really thought about it like that, but she asks if he's still enjoying himself. He admits that he's starting to find the atmosphere a little cold, but she thinks it would be interesting to stay here for a while and see the place in Winter. The Doctor has been asked by the club about whether he's planning to attend the club ball and he told them they'd be on their way by then, but he notices Nyssa's disappointment and she admits she was hoping to go. He immediately changes his mind and tells her they will attend after all. Just then, the Doctor is called away to go for a celebratory pint and he offers to introduce Nyssa to the lads, but he warns her to expect an exciting night of conversation about soccer and cars. She makes an excuse and tells him she has other plans...

At the bar in the cricket club, the Doctor is uncomfortable with Jack continually telling racist jokes, so he decides to call it a night. The group start to mock him unkindly for being politically correct and he argues that all he wants to do is play cricket and it's never been a problem before. Slowly the group starts to turn on the Doctor, accusing him of thinking he's better than them. They tell him he has to put his life into the club and become part of their struggle, but the Doctor argues that it's his recreation, not a matter of life and death. He says he always plays to the best of his abilities, but at the end of the day it's only a game. The rest of the team become quite hostile and refer to him as an outsider, and when the Doctor reminds them that previous Stockbridge cricket club committees didn't think like this, they tell him that's why they were always beaten. The Doctor says the one thing he usually doesn't like about the English character is their willingness to embrace glorious defeat, but in their case... He's interrupted by Jack, who accuses the Doctor of not being English and demands to know where he comes from. The Doctor decides it's time he left and the group taunts him as he heads for the exit...

The Doctor walks away from the lights of the pavilion and into the darkness of the forest. He could leave now, but he intends to remain for just a little longer, because of old obligations and because they're still family and things may change. As he reaches the edge of the ground he bumps into Nyssa and Andrew, much to everyone's surprise. The two youngsters claim to be stargazing, but the Doctor points out that must take considerable skill through the branches of the trees. The young man introduces himself as Andrew Whitaker and says he's seen the Doctor at breakfast. He assumes the Doctor is Nyssa's elder brother, or possibly just a friend, or even a social worker -- but the Doctor says their relationship isn't so easy to define. Rather abruptly, the Doctor tells Nyssa he'll see her back at the guest house, then he walks off alone. Andrew is a little disturbed by the encounter and asks Nyssa if she feels the same way about him. He asks if the Doctor is one of her people, and for the first time Nyssa realises Andrew is starting to believe her story. He admits that the detail in her book proves she's really lived the life she described, but he still thinks she needs a villain. Nyssa is uncomfortable and says she's not ready for the villain yet as that would complete the story. Andrew tells her she should go after the Doctor and she agrees. So why isn't she leaving... ?

The next morning at the breakfast table, the Doctor greets Nyssa with a cheery account of the beautiful weather. He hopes she isn't planning to apologise for last night, but she tells him she wasn't. He says he was young once and he thinks it's all splendid. Nyssa points out that he was rather rough with Andrew and he admits that he doesn't always understand the needs and expectations of human beings, but Nyssa says this isn't true and the Doctor can be incredibly human. He doesn't know whether to be flattered or insulted. The Doctor knows that Nyssa's and Andrew's lifespans are roughly the same and they could have a perfectly happy life together here. He's even noticed that she's started wearing jeans! He suggests she could work in the pub or the betting shop, or even become a successful author of fantasy novels. Nyssa realises there's something else troubling the Doctor and wonders if their season is going badly. He admits that today's match has been called off and the pressure is now on because there's only one more match next week. It's the same night as the club ball, so everything will be decided that night. He came here to experience a particular kind of time, but he's ended up with exactly the opposite.

Andrew tells Nyssa how much he loves to see her writing, but she asks him not to distract her as she's into the last bit. He notices that she's writing much faster now and she tells him she has a deadline. He's clearly disappointed, and she asks him what he'd say if she decided to give up a lifetime of travelling in time and space in order to settle here. He thinks this would be great and points out that no one would ever end up together if they always thought twice about whether it was a good idea. She asks him if he could handle the responsibility of her staying here just for him but he doesn't want to think of it like that. She's worried that he might wake up one day and not want her to be there, especially when she's no longer the "fairy princess" and just someone who works in the pub, but he doesn't look that far ahead and can only think of one day at a time. He's being honest with her, but she finds it all too complicated. She's getting near the end of her book and it's been a long time since she's let him read any of it. She reveals that she's finally introduced a villain -- someone who brings time to the immortals and makes the kingdom come to an end. She wants Andrew to ask her not to leave, but he refuses.

Nyssa visits the Doctor and tells him she's come to see him play today. He's grateful as this is an important game for the team, but she knows he probably would have left earlier if it wasn't for her. He asks if she's looking forward to the ball this evening, but she's not sure. He suggests they leave immediately afterwards and when she complains about been given a deadline, he argues it's more of a choice. Later, the Doctor and the other players are watching the match, but things aren't going too well and eventually it's the Doctor's turn to go onto the field to bat. The light is starting to fade and the only two players left on the Stockbridge team are the Doctor and Don in batting positions. Don reminds the Doctor that if they draw the match, the team will be relegated and he's worried that the Doctor might deliberately lose because of the incident in the bar the other night. Don tells him he's going to announce his retirement tonight as this is as close as he's ever going to get to being on top of his game. He asks the Doctor to help him achieve his blaze of glory.

Andrew joins Nyssa and makes small talk, then apologises again for interrupting her. She tells him she's finally finished the book and she feels strange and a little sad because after she's dead, the book will still be around -- a part of her that won't suffer because of time. Andrew is starting to enjoy the match -- there are three overs to go and the Stockbridge team needs to score twenty points. He thinks the Doctor could be OK, but Don looks like he could pass out at any moment. Nyssa is studying Andrew and thinks she's worked out what makes him the way he is. She thinks it's all about time. Andrew doesn't like to think about consequences, about one thing leading to another. She thinks that will change when he's a bit older, and the Doctor is the only person she knows who ever gets completely detached from consequences. She tells Andrew it's time they got ready for the ball, even though it won't be for hours yet, and he seems surprised that she doesn't want to see the conclusion of the match. Nyssa says the Doctor will either win or he'll lose, but she's got something to give Andrew before she goes. Andrew is intrigued and agrees that it's time they got ready...

The match continues and then suddenly Don cries out in agony. He asks the Doctor to give him a second to recover -- he has no intention of dropping out as they only need to score one more run from this over. It's getting dark, but Don insists that if the other team offers them the light they're not to take it. He tells the Doctor that they must run for anything. The bowler charges towards them and the Doctor hits the ball... and the two men start to run. They achieve their run and the crowd cheers in delight. Then they notice that Don has dropped to the ground and isn't getting up. The Doctor rushes over to check on him and shouts out for someone to call an ambulance... As the ambulance leaves, the team are devastated. Jack is sure Don knew he was having a heart attack and wonders why he insisted on continuing. The Doctor sends someone to change the score card as Don's bat just made it over the line in time. It's what Don would have wanted. The team has succeeded in avoiding relegation, but Don won't be here to see it. The Doctor says that Don doesn't have to be here for the ending -- what's important is that he wrote it.

The freezing bitter wind howls around the Doctor as he goes to close the door of the barn outside. His wife, Anima, urges him to put a jumper on first, but this just starts up an ongoing argument about their choice of clothes. He says he can't recall her ever wearing the same jumper more than once, whereas she complains that all his jumpers are the same colour. He's worried that if the door keeps slamming shut it'll wake their children, Adric and Tegan, but Anima reminds him that he's getting old and can't do things like he used to. He opens the door and notes that there's snow outside as far as the eye can see. The blizzard must be right on top of them, so Anima insists that if he's going outside, she's going with him. He objects, but his wife's a stubborn old thing. As they fight their way through the snow, the Doctor feels tired, almost as if he's carrying someone, but she thinks he's just getting old.

Elsewhere, Lasarti wakes up in bed and calls for his wife Nyssa, but she's in the nursery and tells him to go back to sleep. He asks her what's wrong and she says she was worried about their daughter Neeka, but she seems to be fine. Nyssa admits that she's had the dream again, for the third night in a row. As her husband is a specialist in dreams, he offers to help, but she's told him before that she never wants him to analyse her. She tells him the dream is set a few years ago, from before Terminus and the Corporation Wars -- from her time with the Doctor. Lasarti knows that she went through some bad times, but she assures him it wasn't all bad. Some of it was fun too. She was a child then and it was the start of her growing up. She had to have those adventures and if she hadn't, she'd be dead now or someone who follows science as a sort of hobby, rather than someone who wants to change things. Lasarti asks if her father was in the dream, and Nyssa says he was, just for a moment; it looked like he was trying to communicate with her, like he wanted to take up all the channels and be everything in the world, all at once. Of course it wasn't really him -- it was the virus, the parasite that took him over. She realises this might actually be a genuine attempt by the Master to communicate with her, which is why she's awake and pacing around. But it wasn't just the Master in the dream. Tegan and Adric were there too, and there were others she didn't recognise. And it was very much a dream about the Doctor. Lasarti guesses that she's about to ask if she can use his machine, and she tells him she needs to experience the dream more clearly. She needs to move around in it and stay conscious while it's happening. He tells her to get her coat. His colleagues will be surprised to see him at the lab at this time of night!

The Doctor is frustrated by how long it's taking to get to the barn; even though he and Anima have only been outside for a minute or two, it seems like ages to him. Suddenly the Doctor seems someone out of the corner of his eye -- someone dressed in camouflage, wearing pale white on white and looking very much like a chrysalis, with something more colourful on the inside. Anima can't see anything and thinks her husband's suffering from snow blindness. They reach the barn and the Doctor insists on going inside to check that everything's all right. Inside, Anima tells him she doesn't want to look at the object inside and asks if they can go back to the house, but the Doctor says he's tempted to stay here rather than fight their way back through the snowstorm. Having said that, the nice fire they have inside the farmhouse is very tempting. He decides to listen to his wife for a change and locks the door behind him this time so the object can't knock it open again. As they leave, Anima can't be sure if he's talking to her or talking to himself again...

Back at the farmhouse, Anima tells her husband not to worry as people often think they see things in blizzards. She thinks he works too hard and is getting forgetful, so sometimes he sees things that aren't there. The children have even started to make jokes about it. He's not happy that his wife is pointing out his mistakes, but she says he always used to like the fact that she had a mind of her own. He insists that he wants to stay here and she wonders whether he's expecting something to come and haul him away. Perhaps that thing out in the barn? Anima doesn't think that's going to happen unless he actually wants it to. She suggests he sort out the feed for tomorrow to keep his mind occupied, or there are some sacks that need mending. He decides to leave that for now, nor is he keen to oil his bat to stop it warping over Winter. He's getting too old to play now anyway, although she doesn't think he'll be saying that come the Summer. She tells him it's time for bed.

Later that night, the Doctor wakes up with a start after a bad nightmare. Anima tells him to go back to sleep, but then he starts to hear Nyssa's voice calling to him. At first he doesn't recognise her and demands to know what she's doing in his house, then he starts to find her voice more familiar. She introduces herself and tells him he's inside one of her dreams -- but he insists it's the other way round and she's actually inside his dream. Nyssa explains that she's asleep and is using a device that her husband developed to consciously explore one's dreams. The Doctor thinks Nyssa reminds him of the daughter he lost. He starts to count them, but loses track of how many children he's lost over the years. Nyssa wonders what all this says about her subconscious, but dream or no dream, the Doctor invites her down into his parlour. Nyssa is fascinated to find that she's inside a farmhouse, although certain aspects of it still feel like the TARDIS. There's a hatstand in the corner and the dishes have been arranged on the walls all around the room. The Doctor doesn't know what the TARDIS is, but he's certain Nyssa is a very odd apparition because she seems to think he's the person appearing in her dream. She asks if he has a message for her about her father, or about the Master. The Doctor assumes she's referring to a character on the television, whose adventures his children follow twice a week. He wonders why his dream is asking him such odd questions and she insists once again that he is the dream, not her. This is all getting rather philosophical so the Doctor offers Nyssa some cheese so they'll at least be able to dream on the same wavelength.

They eventually agree it's far less tiresome to treat each other as if they're both real, but then the Doctor makes a reference to Lewis Carroll, which Nyssa doesn't recognise -- which proves that it can't be her dream after all. Apart from looking a bit like the TARDIS, she agrees that she's never seen a building like this before. He tells her that it's a working farmhouse; they have animals in shelters down in the field who forage in the forest at the front, and at the back there's a cricket pitch where he plays, although it's under snow now. And then in the old barn out the back they have a coffin. Nyssa is momentarily stunned, especially when the Doctor explains that a coffin is a machine for exploring forests -- "Go softly on" -- the way one's whole life flashes before one's eyes before one... dies. The Doctor starts getting confused. He knows he needs to be carried in the coffin, but he still feels as though he's carrying someone himself. Suddenly he collapses, but he tells Nyssa not to worry as he often has funny turns like this. He says he's getting old and his speech centre is getting confused, but there's still an active mind inside. He doesn't want to wake his wife upstairs as she gets frightened by change.

They hear a noise, and the Doctor tells Nyssa that it's a ghost and this place is haunted. He often sees them when he's sitting up working at night, but they're harmless and he thinks they're probably just memories. Every now and then one of them tries to scare him, but he's past scaring now. Nyssa observes how old the Doctor is looking, but he's quite comfortable with that as people always told him he was old before his time, like an old man inside a young man's body. Now he is what he's always been, and he intends to stay that way. The ghost starts to come downstairs and the Doctor asks Nyssa if she's ready to meet it... but it's Lasarti who appears at the bottom of the stairs and greets Nyssa. She's angry as she told him not to follow her, but it's too late now and he's realised her dream was about the Doctor after all. Nyssa introduces the Doctor to her husband and explains that he's a dream research scientist. The Doctor is pleased as Lasarti looks to be a very nice young chap. Lasarti immediately picks up on the fact that the Doctor claims not to know his old companion. Nyssa suggests trying an experiment -- she wants to switch off the machine and if this is indeed just a dream of hers, she should wake up. She completes the task and everyone is surprised to see that they're all still here! Lasarti says that's not possible, but when he checks he confirms that the power is off. Nyssa suggests this might be some sort of shared psychic experience, but Lasarti points out that if it is, why wouldn't the Doctor know who's communicating with him?

Nyssa thinks the Doctor looks lost and distracted and she urges him to listen to them, but the Doctor is busy trying to establish where he is. He thinks the farmhouse is very 'generic' so they could be anywhere and at any time. Lasarti decides to shock the Doctor into waking up and he deliberately smashes an ornament, but it has no effect other than to make the Doctor worry about waking up Tegan and Adric, who are sleeping together upstairs. Nyssa is again shocked by the revelation, until the Doctor explains that they're his children. She's not sure why exactly, but she could never imagine the Doctor having a wife. But when she asks what her name is, the Doctor can't remember. At first he thinks his wife is Peri, then he changes his mind and says she's Kamelion. He gets even more confused as he knows the names are important, yet they mean nothing to him. He rushes off upstairs to check on his wife, leaving Nyssa and Lasarti downstairs, bemused. As a scientist, Lasarti finds the situation exciting, but it's way outside his comfort zone, so they both decide to follow the Doctor...

They track the Doctor down in the nursery where he's looking after the two babies, Adric and Tegan. Nyssa thinks they're lovely, but Lasarti is worried about the gold star, which looks a bit sharp. Nyssa reveals that she's a mother herself now and she wishes the Doctor could see her baby, but the two children here are not the Adric and Tegan that the Doctor used to know. The Doctor says they've still got a lot of growing to do, but there's something in the way of him getting born... or dying. Suddenly they hear the sound of maniacal laughter coming from outside and the Doctor rushes back downstairs to make sure whoever it is doesn't get in.

Outside in the blizzard, the Doctor calls out to a distant figure and asks why it won't come any closer. Lasarti tries to bring the Doctor back inside, warning that they're in life-threatening conditions. Nyssa tries to see who the Doctor is shouting at and he points to a figure dressed like a mummy, all bound-up in white, who's standing by the edge of the field. This time Nyssa and Lasarti can see him, circling the area. They hear the evil laughter again, as if it was coming from right out of the sky. Lasarti realises that if the actual world is influenced by the experiences they're having in here, they can't expect help from outside because of the extreme weather conditions. They're completely cut off, they're facing an unknown enemy and they have no weapons. Nyssa suddenly recognises the figure in the distance and she urges the Doctor to remember too -- but the Doctor doesn't want to know. He has a proper life here and he doesn't want to run from place to place any more. This is the kind of existence he's always wanted... isn't it? The Doctor bemoans the fact that he hardly ever had the time to play cricket. Every time his people change, they change into something more comfortable, more appropriate to the conditions. He was made for an existence in linear time, for births, marriages and deaths -- and he's been denied this! This doesn't sound like the Doctor that Nyssa knew, but he believes the life he's got here is everything he's ever wanted. A wife, children, a home, a life based in time and surrounded by seasons. Nyssa reminds him that "everything I've ever wanted" is something found only in children's stories, and now she realises whose maniacal laughter they've been hearing. Nyssa believes they're in a trap and the Doctor realises he needs her help. She tells him that they met the mysterious figure when he regenerated, and he called it a Watcher. The real Adric and Tegan were there too, and the memory of his friends finally allows the Doctor to remember Nyssa. He remembers that they travelled in the TARDIS, but he still needs more time to piece everything together -- but Nyssa warns him they're dying of hypothermia. The sound of the barn door slamming open again reminds Nyssa of his earlier comments about having a coffin in the barn and they decide to investigate...

When they enter, Lasarti is surprised to see that there really is a coffin inside, especially as it's floating in the air and jumping around. Nyssa thinks there might be something inside trying to get out, but the movement reminds the Doctor of a heartbeat. It also reminds him of a joke about a man who was being followed by a coffin, and ran into a chemist and asked if they had anything to stop this coughin'. Lasarti has heard it before, but Nyssa doesn't get it. Lasarti is pleased that it's warmer inside the barn, but the Doctor points out that it's even warmer inside the box. Nyssa is sure that the answer is here somewhere and that everything they've seen has a context. She understands why the Doctor wants to stay with his family, but she also knows this is all an illusion inside his mind, and she and her husband are trapped here too. The Doctor tells Nyssa that she's found a home for herself and is settled, and asks whether she would give all that up to be a wanderer again. She says she wouldn't, but unlike her life back home, nothing they're experiencing here is real. The Doctor agrees and becomes angry at the idea that someone thought he could be so easily trapped in a scenario so simple and trite. He goes to the coffin and asks Nyssa and Lasarti to help him climb inside. Suddenly Nyssa realises it's a Zero Cabinet, a device used to help Time Lords regenerate.

Once inside, the Doctor's mind immediately begins to clear, and he realises the Zero Cabinet isn't real either but is based purely on his memory of one. He becomes rational, and thanks his friends for visiting him and apologises for the mess inside his mind. He's currently regenerating; at this very moment, he's just fallen through the doors of the TARDIS on the surface of the planet Androzani Major. He tells them about the antidote to the spectrox poison and explains that he's just given the last of it to his new companion Peri. Unfortunately the supply of blood to his own brain has halted and the poison is breaking down his nervous system. He's been holding off the effects for the last hour in order to give himself time to save Peri, but everything that's happened inside his mind has taken place over just a few seconds. His brain is dying and he doesn't have long, but he couldn't wish for better company. It feels different this time, and he was reaching out across time and space to get support from his friends to add their energies to his own -- but something or somebody is trying to block the regeneration. The house was created to distract him from the outside world during the few seconds of hallucination that a Time Lord experiences during the onset of regeneration. It might have worked, but whoever's causing this has underestimated the Doctor again -- he didn't appreciate how much the life of a wanderer feels like "home" to the Doctor now, because the man responsible hates being alone himself so much. Nyssa realises that the Doctor is talking about the Master. The blizzard was his attempt to cut the Doctor off from those who might be able to help him and he was only able to make contact with Nyssa because Lasarti's machine boosted the signal. Nyssa asks how they can get out of their predicament and help the change. The Doctor asks Lasarti to burn down his home and destroy the trap. He has another job for Nyssa and asks her to help him up.

Lasarti goes back to the farmhouse and calls out to anyone that might be listening, warning them to get out now, as he has no wish to harm them, even if they are illusions. He starts the fire and within seconds the entire building is ablaze. Suddenly he sees the Doctor's wife, but she appears in the form of a mass of distorted silver. In Anima's voice, 'she' introduces herself as Kamelion, and although she appears to be in pain, she urges him to continue his mission to destroy this place. She explains that she was part of the Master's plan; her mental link to the Doctor was the channel between them. But now she's free, as Lasarti and Nyssa's presence here has given her the strength she needs to resist. Kamelion adds that whatever the Doctor may have told them, these few seconds of illusion were more precious to him than he realised. He may fight the idea of living in time, but it is a part of him, and the children were the manifestation of the mental connections he sought across time and space, the links to his other companions. Kamelion was forced by the Master to hide Adric and Tegan from the Doctor by making them appear as children, but now they are free to contact the Doctor to support him. Kamelion thinks of the moment of his own death, severs his link with the Master, and dies as the farmhouse starts to collapse around Lasarti.

As the Doctor takes Nyssa into the forest to meet the Watcher, he can sense the presence of Kamelion for the first time and realises the android has sacrificed himself once again to finally break the mental connection that allows this place to exist. He can also feel his other companions starting to break through to help him, but it will do no good unless they can find the next person that he's going to be. Again, he can sense an array of colours inside the white shape, but he collapses in pain. If they can't find the Watcher soon, he'll die for good and unfortunately he'll take Nyssa and Lasarti with him as his brain structure collapses. Back in the real world, Peri is stuck in the TARDIS and she too will be trapped in the Vortex forever without the Doctor's help...

Slowly the blizzard starts to fade and the Doctor realises the interference has stopped. He can feel all his friends reaching out to him across time and space -- first Turlough, then Tegan who's safely at home and is wondering what he's doing inside her mind. She knows it's important, though, and is willing to give anything to help, including her life. Nyssa tells the Doctor that he's needed and he mustn't die, and Turlough points out that many of his enemies would delight in his death. Eventually they spot the Watcher in the woods. Nyssa wonders if the Doctor can tell what his new body is going to be like just by looking at him and he says he can guess, as each life creates the next. There was a moment not long ago when it looked as if he was finally going to get off the wheel of life, but Nyssa was here to put a stop to it. She tells him she's very proud to be a part of his family and he confirms that she was the most vital part at the end. So, what happens now...?

As soon as Nyssa and Lasarti are back in the real world, they check on their baby and are pleased to see that she slept through everything. Now Lasarti can finally say that he met the Doctor and he understands why Nyssa always talked about him the way that she did. Sometimes he's like a legend and sometimes he's like a best friend. Nyssa says he pops up in human time -- the linear time that gives us deaths and babies, old relatives and long-term illnesses -- and he also lives in mythological time -- circular time, where the seasons die and resurrect, and where people who exist in stories live forever. Lasarti had woken up in a hospital bed, ducking from burning timber, so Nyssa never got the chance to tell him what happened out in the snow. He asks how the story ended for her...