The TARDIS lands on a deserted beach under a green sky. The Doctor steps out and surveys this otherwise Earth-like planet in Galaxy Seven. It is late afternoon, warm with a stiff breeze. He turns from the sea and looks at the ruined city of Arcopolis. This vast city was once home to 200 million people but now it stands deserted. He has landed the TARDIS as close to his intended destination as he dares and now must make his way on foot through the city. The buildings are immense, reaching almost impossibly into the sky in a plethora of impossibly beautiful designs. The whole thing speaks of a long-lasting, prosperous and peaceful society. Unfortunately, the overgrown plant life, broken windows and collapsing walkways are a testament to the sudden end that wiped out the whole population fifteen years earlier.

The Doctor makes his way into a seafront apartment block and moves up through the floors until he can see his target. Ten miles away at the heart of the city stands The Fortress. It is a huge building, twice the height of even the highest neighbouring skyscrapers. Even from this distance it is possible to make out the towers and gun turrets that bristle around the immense black pyramid. Obviously alien and full of menace, it would daunt any sensible person. Nevertheless, this is where he must go.

Back on the beach a transparent, ghostly hand with six fingers reaches out to touch the TARDIS.

The Doctor picks his way carefully through the collapsing walkways and rubble of the nearest buildings. In some soft mud he spots a recent footprint: six toes are clearly marked. A movement in the street bellow attracts his attention and he descends. At first the road is as deserted as he would have expected until a group of children, the eldest in their early teens, emerge. They attack him with bricks an planks, shouting that he is a ghost and warning each other not to touch him.

He tries to engage them in conversation, pointing out that he is not a ghost but also asking if any of them have six toes. The children stare at him blankly and ask if he knows about ghosts. His reply, that he has met many things that people thought were ghosts is misinterpreted by the children to mean that he helps ghosts. Only one of the children, a stocky girl, hangs back when some of the boys launch another assault on the Doctor. He wishes out loud that he could see a ghost and to his amazement one appears. It seems to be a shimmering shape of a man in a toga, terrifying and terrified. The Doctor reaches out to it with his hand but a boy who had been about to attack the Doctor with a piece of metal pipe warns him not to touch it. The ghost sweeps its hand round and touches the boy. Instantly the boy vanishes. Moments later the shimmering figure fades too and the children flee, screaming.

The children regroup in a nearby building, gabbling in fear at what happened. Only the stocky girl remains composed. She knows that the man who called himself the Doctor is different to anything she has heard of before and therefore significant. She uses her mobile communicator to call Professor Jeffip. At first the professor is annoyed that Alsa is wasting precious batteries to call him. He listens to the story of Frad's death at the hands of the ghost but only becomes interested when he hears about a stranger, the Ghost Doctor. He tells her to use the comm device to take a picture of the stranger and send it to him. Alsa sets out to track the Doctor. One of the older boys, Gar, follows her. He talks about how good the Doctor was at fighting. Alsa disagrees saying that he didn't hurt any of them even though they are only children but Gar explains that eight of them tried to hurt the Doctor and none of them even hit him.

Alsa and Gar use their knowledge of the city's layout to gain a good vantage point to see the Doctor. They are confident they will find him soon but are perplexed when he doesn't appear below them. Suddenly he appears behind them. In fact, he had been pondering the problem of getting to the Fortress. His optimistic estimate that it would take him three hours to walk the ten miles has proved woefully inaccurate. In an hour he had gone barely half a mile. As well as the difficulties of a collapsing city he had had to deal with feral, if well dressed, kids. When he saw Gar and Alsa he decided it would be better if he spoke to them again.

Alsa begins by asking if he killed Jall. The Doctor says he didn't and asks who she was. Alsa says that Jall was a girl who died a few days earlier, apparently of fright the parents said. Alsa then asks what the Doctor is doing there. He says he needs to get to the Fortress, which makes no sense to either of the children; nobody would choose to go there. They tell him that the Fortress just appeared in the city fifteen years ago, before they were born. For three days it remained dormant and then suddenly everyone in the city vanished with the exception of thirty seven adults ('the parents') who were underground in a travel tube. All the birds, fish and animals vanished at the same time. The computer systems and generators all failed at the same moment. Nevertheless, the Doctor says he must get into the Fortress even though it will be incredibly dangerous to do so.

Alsa asks if she can take a picture of the Doctor. He lets her and asks to see the comm device she is using. He takes it from her and then seems to see something in the distance. While the children are distracted the Doctor sneaks away, taking the comm with him.

The Doctor uses his sonic screwdriver to access the comm device. He finds out that there is no local internet and only one communications mast (which Gar has told him his mother maintains). Consequently, he is left to make his way alone to the Fortress. After a few hours he arrives at an archway that opens onto a recently formed lake. This water is all that stands between him and the Fortress. The lake is a mile wide and yet, about half way across, he can make out the figure of a glass man. At first he thinks that it is a statue until instinct tells him that it is alive. Wondering if this is another type of ghost he shouts to it. Immediately, a bolt of energy streaks across the water towards him. Dodging away into the archway he nearly collides with Gar and Alsa. They are screaming because ghosts are following them. Alsa runs pat the Doctor and through the arch. The Doctor spins quickly and tackles her to the ground even as another deadly bolt slams into the wall where her head had been a moment before. She stares at him breathlessly and says that they shouldn't have come here; nobody survives this close to the Fortress. She accuses the Doctor of stealing her comm but is astonished when he returns it to her with a fully charged battery: this seems impossible to her.

He looks at her, a thirteen year old girl in a pinstripe suit. He realises that all the children seem so well dressed because they have raided the city's shops. Alsa agrees and says that the children do not see it as stealing although their parents disagree. They think that the children should learn to make things for themselves. The Doctor shows some sympathy for that viewpoint. He points out that the children do not know what it is like to lose everything. For a second he has a memory of the sudden flash that annihilated the Time Lords.

He then talks about the Fortress. He tells Alsa that it is automatic. Motion detectors fire the energy rays and the ghosts are defensive images projected to scare away any people who get too close. Gar is intrigued by the Doctor's knowledge and asks him to tell a story about similar adventures he has had. The Doctor tells him about a recent encounter he had in London where he fought the last survivor of the Steggosians (a breed of fascist dinosaurs) in Big Ben in London. The Steggosian fell to his death and so a whole race had perished.

Very slowly, so as not to attract the attention of the motion sensors, the Doctor leads Alsa back to the safety of the archway where Gar is hiding. She tells the Doctor that he must come back to the parents with her. He says he can't because he must get into the Fortress and disable the weapon inside that killed everyone in Arcopolis. Night has fallen and he turns to take his leave of the children, which is when Alsa brings a slab of concrete crashing onto his head.

He wakes up in a camp bed in a room that resembles a cross between a hospital ward, a machine shop and a laboratory. Half a dozen very young girls in lab coats are cleaning up some scientific equipment. When they see that the doctor is awake he is taken to meet Professor Jeffip. The Doctor, wearing borrowed pyjamas, finds the professor analyzing the sonic screwdriver. He tells the Doctor that he was brought in by Alsa and gar in a wheelbarrow. The professor says that from the Doctor's two hearts and a pocket full of exotic items he has concluded that the Doctor is alien to the planet. He adds that they knew on Arcopolis that there must be extraterrestrial civilizations but had yet to encounter one. He wonders why the Doctor has come. He asks what the Doctor knows of this world. When the Doctor says he saw a boy killed by a ghost the professor responds that at least it wasn't a girl.

They walk through the tents that make up the encampment. It is situated on a riverbank which houses a waterwheel to power their lathe and looms. Jeffip says that they mainly use it to irrigate their crops. Nearby, three women are sitting on a bench. Two are heavily pregnant and they are surrounded by a crowd of small children. The Doctor soon finds that each of them has had more than a dozen children. The one who isn't pregnant, Dela, has given birth to sixteen since the cataclysm. An older woman, Jennver, arrives. She has no children but is the group's obstetrician and leader of the council.

The Doctor surmises that it is the duty of the women to produce children as often as possible by multiple fathers. The girls are valued more highly than the boys who aren't even taught to read. The eldest of the girls are approaching child bearing age but Jeffip calculates they need only produce ten children each to maintain the society.

They live in a park, two miles long on each side. It is surrounded by skyscrapers though the Fortress is visible in the distance. The Doctor, Jennver and Jeffip walk through the park discussing the Fortress. Jeffip has a number of theories, including the idea that it may have come back from their own future. Not only did it kill 200 million people on their world but it obliterated nine stars. His own theory is that they were caught in the crossfire of an intergalactic war. The Doctor remains silent on this issue.

Later, the Doctor asks Jeffip about Jall. She was one of the first to be born and was murdered two days earlier. Jeffip is puzzled by her death: instead of disappearing, her remains were found almost intact. Something that puzzles the Doctor is the fact that the parents refuse to enter the city at all, even to find medical supplies, but insist on building a subsistence culture from what they can produce themselves. On the other hand, it seems to be a rite of passage for the children to go into the city and scavenge for what they can find.

The Doctor has retrieved his clothes by the evening, though not his possessions. He is taken to a meeting of the council where he meets about ten other surviving adults. It is obvious that they assume he will fit in with their society and stay with them, using his gifts to enhance their lifestyle. He tells them that is not his intention. He has come to destroy the weapon in the Fortress. Alsa, who has joined the meeting, says they should let him go to the Fortress: once it is disarmed the city will no longer have the threat of the lightning and the ghosts and they can inhabit it again. Suddenly the Doctor realises that Alsa also thinks he can use the Fortress's power source to re-power the city and bring the old machines back to life. He says that is not possible, the Fortress is powered by the weapon, not the other way round.

However, this sets some of the parents thinking. Some see a chance to harness the power and others think of using the weapon for their own defence in the future. The Doctor shouts them down. He says this is the last weapon of its type from a war that destroyed both sides. He tries to explain what the weapon does - it not only kills the enemy but eradicates all trace of them, including the memories of them held by anyone who might have seen them (even unknowingly) or heard of them. In order to do this the weapon must kill its own side, too, for of course they have heard of their enemy. It was a weapon of last resort only to be used when all was lost. The question is, why had it not continued on to wipe out the galaxy or even the whole universe. Somehow the parents who had survived must have been underneath it in their travel tube at the moment it fired, and therefore within a protective force field. Why it hasn't fired again is a mystery and he intends to disarm it before the occasion arises. He says that the event which destroyed the civilization on Arcopolis was a massacre so great that great that the deaths of 200 million people went unnoticed by the historians of the galaxy. After this, he turns and storms out of the meeting.

After the Doctor's departure it appears that the power dynamic in the council has changed. Jennver's insistence on building a new, subsistent society is over-ruled by Alsa's desire to utilize the Doctor's skills to power up the old city. The other parents point out that they have been forced to live in a way that they have not chosen so why shouldn't the Doctor?

The Doctor meets Dela in the compound, on her way to the council meeting. He tells her that he is leaving and she asks him to take her with him, not just to the Fortress but out to the stars. He refuses but she follows him through the tents as he goes in search of his possessions. By mistake he turns into a room where a corpse is lying on a bed. It is Jall, Dela's eldest. The dead girl has had her eyes removed but by a process which is far beyond the technology of the planet.

After finding his TARDIS key and other things, the Doctor steps out into the rainy night. He promises Dela that he will find whoever it was that killed her daughter and punish them. He passes into the city.

On his way he sees various gangs of (mainly) boys but they don't react to him. He finds it hard to hear whether he is being followed because of the rain gushing from blocked gutters and broken pipes. By midnight he has arrived in a wide plaza. In the middle is a transparent man with six fingers on each hand. He tries to talk to it but the glass figure turns and runs. The Doctor follows but soon loses his prey in the network of empty buildings.

Gar wakes Alsa and together they cycle to the Car Factory. They have commed the children in the city and kept a track of the Doctor's progress. It takes them two hours to get there with a number of other children so they arrive well before the Doctor. The car factory is a huge circular building that stands 130 storeys high. The Fortress appeared in the factory, neatly slicing through the walls. From a walkway high above the ground they see the Doctor's approach. He comes from the side furthest from the lake where the Fortress's 'lightning' bolts can't get him.

He makes his way through the wide, curved floors of the factory, passing the defunct robots that worked there. Eventually he reaches a section that is blocked by one wall of the Fortress. He uses the sonic screwdriver to resonate the concrete in the ceiling nearest to the Fortress. Pieces crumble and fall. A shot from the gun mounted in the Fortress wall disintegrates the concrete but also causes much larger sections of roof to collapse, disabling the gun. The Doctor saunters up to the Fortress and uses his screwdriver to open a hidden door, and then passes inside.

The children hear the noise of the gun and the rubble falling and think that the Doctor has planted a bomb but Alsa says he wouldn't do this. They are shocked when Jeffip and some of the other parents walk up to them, having set off almost as soon as the children - this wasn't in Alsa's plan. With Jeffip are Dela and a man, Fladon. It is Fladon who leads them down to the level where the Doctor entered the Fortress. They find the tiny gap where the Doctor went in and Alsa, despite their warnings, squeezes through it. She finds herself in a corridor where the Doctor warns her to stay back or they will be killed by one of the many internal defence mechanisms. He tells her that she has as much chance of setting things off if she goes back so tells her to follow him.

Outside, the three parents and the children (Gar, Coz and Moz) are perplexed when a transparent glass man suddenly walks up them. He walks up to Dela and she sees, in his transparent head, the eyeballs that were taken from her daughter. Dela screams. Outside, through the enormous curved window, they see three huge spaceships descending through the sky. Inside her head Dela hears the glass man tell her, "We are the Eyeless."

The Fortress is not an intelligent machine. Rather, it has a series of eventualities programmed into it, each with an optimal solution. Therefore, having detected the presence of humanoids within its walls it simply decided that they were little threat and left it to the multitude of defences to eliminate them in due course. As such, the Doctor and Alsa continue their slow progress down the corridors into a circular room. The Doctor borrows Alsa's comm and projects a hologram of the Fortress. While showing the internal structure it also details the nearby buildings as well as three spaceships hovering close to the outside wall. The comm also contains the single word "Eyeless." The Doctor has rarely been to Galaxy Seven and has never heard of them before.

Alsa hears a voice telling her not to move. She tells the Doctor, who has heard nothing. They turn and see three glass men walking down to join them. They have read Dela's mind before entering and know that the Doctor is a threat. They communicate through a psychic link but the Doctor's Time Lord psychic defence is blocking them. Alsa translates what she is learning from them: they are an explorer race which forages for technology, usually by agreement but sometimes by force. They tell her that they want the Doctor's time machine. He blusters that he is a 'Thyme Lord' with a speciality in using herbs and, unbelievably, they accept this. One of the Eyeless is the one wearing Jall's eyes. They tell Alsa that they take trophies from the situation where they are the first among their people to experience something new and then display them within their bodies. Alsa has recognised Jall's eyes but is unconcerned by them. The Doctor is perturbed by this and offers Alsa one chance to decide who she sides with; the Eyeless or him. The contemptuous look she gives him is all the answer that he needs.

Before they can react he steps forward and with his screwdriver brings a door crashing down behind him. One of the Eyeless lunges forward to catch the door and the Doctor runs. He can tell by the footfalls that only one Eyeless got through before the door closed.

The Eyeless with Jall's eyes speaks to Alsa, swapping consciousness with her briefly to show her what it is like being one of its species. In the process it learns that the Doctor tricked it about being a Thyme Lord. It also learns to feel anger in the way that Alsa always does. Alsa learns that the Eyeless only came to the planet originally to take the TARDIS. Having detected a hypercube in flight they overtook it and landed two days before it arrived. Alsa is surprised: she thought they came to get the weapon in the Fortress. This is the first time the Eyeless has heard of the weapon and it is intrigued.

Having dodged a snare that traps his pursuer, the Doctor glances at the comm device. It says HELP. He sees the ghost of a beautiful girl in front of him. Using the comm keypad he talks to her. It transpires that she is Dela's former girlfriend, Gyll. Despite the fifteen years since her death Gyll thinks she has been lost (not dead) and for only fifteen minutes at most. Unable to decide whether this is really Gyll's ghost or a trap set by the Fortress he promises to return for her and carries on.

Alsa and the Eyeless make a deal: if she helps them they will give her an engine to power the city. Eager to learn more of her new friend she asks for one of its memories. It recalls how it murdered Jall and took her eyes as a souvenir. She doesn't enjoy this but starts to feel, like the alien, that the experience was neither good nor bad. As a bonus the Eyeless gives her the knowledge to be an obstetrician so that she can challenge Jennver's unrivalled power in the camp.

Outside the Fortress the Eyeless party alert the Arcopolians that their ships are about to attack the Fortress. Jeffip tells one that he cannot allow this to happen. The Eyeless raises its palm and points a disc mounted there at the professor, killing him instantly.

Inside, the Doctor has noted from the comm display that the attack is about to begin. He does not expect it to succeed but thinks the Fortress may be easier to traverse if it is otherwise engaged. He hurries on.

The three ships concentrate their weapons onto one spot on the wall of the Fortress. It proves ineffective. The Doctor sees a big change inside as the machine switches from standby mode to fully operational. Lights come on throughout the structure, new traps spring into place. A glass arm reaches round him and crushes his windpipe.

The Fortress fires a beam of energy at one of the Eyeless ships. It produces no effect so it fires a second, stronger beam, and then a third. This last one punctures the hull and causes the ship to list briefly. Seven more turrets open fire and rip holes in the decks. As the ship drops back from the other two the Fortress analyses the interior of the ship in a split second and then unleashes a single shot at another ship, destroying it instantly. The third ship blasts the Fortress's guns, ripping them apart. This is unacceptable to the Fortress because it has no remaining weapons on the side facing the two Eyeless ships.

In the centre of the Fortress is a cylinder that runs from floor to apex. Half way up is a chamber that houses the weapon. The schematic on the comm has shown the Doctor that an elevator leads to this chamber. He is currently wrestling one of the Eyeless on a gantry that leads to the elevator. They struggle together into the lift and the doors close. The lift begins to move as the Doctor manages to pin the Eyeless down. He looks at the comm device which shows the elevator moving up even though he can feel it going down. He realises that the Fortress has been using the comm to lie to him. He tells this to the Eyeless and says the only way that they are going to survive is if they work together. The alien seems to agree to this. The lift stops, tips forward and the door opens. They fall out and drop ten metres. The Doctor is winded but the Eyeless shatters into pieces.

The Doctor is lying on bedrock at the bottom of the Fortress in a groove cut for giant wheels that are used to turn the Fortress around. As he becomes conscious of this he also realises that the machinery is in operation, the whole structure is revolving and one of the wheels is approaching. Unable to move he waits to be crushed to death, only for it to halt inches from him.

In the Car Factory the Fortress's spin has brought parts of the building crashing down. Dela, her children and Gar run away but Fladon is killed by a gun that replaces the one the Doctor disabled. Outside, the Fortress turns its weapons on the third Eyeless ship and destroys it. Then it attacks the remaining, damaged, ship. This one has thrown up a protective force field that saves it momentarily. Unfortunately, the power of the weapons that hit it throws the ship back into a skyscraper where it disintegrates. Its fuselage crashes to the ground while its engine breaks free (a huge, sun-like sphere that hung under the craft) and flies back at the Fortress, impacting with one of the walls.

The two Eyeless who are standing with Alsa barely have time to register their anger and resentment at the deaths of so many of their kind before the wall beside them buckles in crushing all three of them.

The sphere breaks through the walls above the Doctor and splashes against the central column. He uses the distraction to gain a few seconds.

Alsa has a bloody nose but nothing worse. The two Eyeless have been joined by three others from outside. They are all aggrieved at the deaths of so many and are unable to reach any survivors with their minds. Persuaded of the value of the weapon they call up a plan of the Fortress as detected by their sensors moments before their ships were destroyed. They calculate that if six of them rush the chamber housing the weapon one of them will probably survive. Alsa is horrified to realise that they are counting her as the sixth person in their party.

Dela and the children reach the cover of some trees near the Fortress. They see dozens or more Eyeless making their way to the Fortress. Dela realises she cannot abandon the Doctor and tells the boys to go home without her.

The Doctor finds two homing missiles chasing him around the large chamber. He manages to dismantle one in flight with his screwdriver but the other is about to hit him when it impacts with the head of a ghost that materialises in front of him. Ghost and missile vanish abruptly. More ghosts appear around him, too many to count.

He tells the ghosts that if they touch him he will die. They back off but still crowd around them. He checks the sonic but they don't even register. He is sure they are not part of the Fortress but cannot be sure what they actually are. He apologises, saying there is nothing he can do for them. Angrily, he tells them that he is the last of his race, whereas dozens of their people survived. He thinks of the millions off Daleks that somehow came through the Time War and tells the ghosts to leave him. They do.

Alsa realises that the Eyeless plan, to charge down a walkway that spans the chamber at the guns, is not the answer. In fact it is not even human. She comes to see that they do not hold the answers she was hoping for and turns to leave. The five remaining aliens absorb her anger and turn to run at the guns. Four of them are picked off by the guns but the fifth reaches the opening into the chamber when it is lifted off its feet by the Doctor carrying an anti-gravity device he has taken from the first rocket. The two of them fly up and then descend slowly to the walkway. The alien aims a punch at the Doctor who inserts the device into a wound in the alien's upper torso. It is blasted into the air where the internal guns of the Fortress have it in full view.

Now that the Doctor has the weapon at his mercy he pauses. Like him it is the last of its kind. He thinks of the Steggosian that died at his hands, the Racnoss and the Pyroviles as well as the Daleks plunging into the Void and Richard Lazarus. He reasons that they were monsters, intent on destroying whereas he is a force for good. He wonders if, with study, he could use the weapon to return the 200 million people of Arcopolis. He places a glove over his hand so that his flesh will not touch it, removes it from its cradle and places it in Alsa's bag which he is still carrying. The Fortress returns to darkness as its power source is removed but before it does he glimpses an army of Eyeless charging down the walkway towards him.

By the time the first three reach the chamber the Doctor is gone. As they reorient themselves in the blackness they feel him pushing through their midst. Four plunge to their deaths and then a flash of blue from the sonic screwdriver warns them of his whereabouts. Before they can react, a section of pipe that he has dislodged drops onto the walkway, eradicating nineteen more of them. The pipe has bisected the line of Eyeless. The Doctor climbs onto it and walks backwards, causing it to roll forwards. It pushes the half of the aliens in front of him back along the walkway until they are forced out of the door. The Doctor is trapped in the vault with more than thirty aliens. He climbs a cable and goes up four levels to a platform where he lies down to rest.

He knows that the Eyeless have been transformed by their meeting with Alsa. The anger that burns in her is now a part of them. He has to stop them from returning to their people where the emotion will spread throughout the civilization making them far worse than foragers. He contemplates using the weapon but that would make him no better than a Dalek.

Just then, the ghost of an old lady appears in front of him, its spectral light alerting the Eyeless to his whereabouts. He crawls through a hatch in the wall and arrives on another platform on the other side. There he meets the ghost of Gyll and others. He tells her that he cannot save her as he had promised. The complicated effects of the weapon removed the people of Arcopolis from reality but left traces of them behind. Anything they touch will be removed from reality but they can never be returned to it. As he speaks the Eyeless approach from behind him but are held back by their psychic ability to read the torment of the ghosts. The Doctor tells Gyll that Dela made a new life and had children but the firstborn was killed by the Eyeless.

Understanding their part now, the ghosts attack the Eyeless. As they touch the aliens the ghosts vanish, one by one, but each time they do this the Eyeless are weakened until they shatter. By the time the last ghost is gone only one Eyeless remains. Of course, it is the one with Jall's eyes embedded in its head. The Doctor offers to do a deal with the alien. He says that if the Eyeless will let him destroy the weapon he will give it the key to the TARDIS. The alien, greedy for the prize, reaches out for him. It knows that there is some connection between the Doctor and this weapon, something he has not said. It reaches into the bag for it and the Doctor puts down his hand to stop it. A hand touches the weapon and it fires. The Doctor is alone.

The Doctor emerges from the dead Fortress. He wonders if the weapon has killed anyone else apart from the Eyeless. Perhaps he is alone on the planet, even the universe. He stops by a giant sonic screwdriver, part of the car assembly plant. He adjusts some of the controls to give himself something to do. Dela finds him here and they embrace while he tells her that Jall's killer is dead and that he has the weapon. He adds that it has now twice failed to do what it was designed to do. He thought everyone might be dead apart from him. Dela looks about and comments on how much she misses birdsong. Alsa strides up behind him, tugs the bag off his shoulder and knocks Dela down with it.

She asks him if he killed all the Eyeless and he replies that he doesn't know. She tells him she thought he was the saviour of her planet. He replies that everything works out for Arcopolis; her people go on and thrive. She demands to be treated like an adult and taken seriously. Maybe, with the weapon she will be. The Doctor snaps back that he can do serious if she wants. He points his screwdriver at the machine above her. Bolts begin to loosen and the girl stares up at the huge weight above her. She dares the Doctor to kill her but he says he couldn't. She opens the bag and looks at the cylinder inside. He asks her if she could use it to kill anybody. All she has to do is think who she wants dead. It dawns on her that this is how the Doctor lives his life all the time. She hands the bag and weapon back to him. Dela, recovering, tells him to destroy it. He says he has to get back to the TARDIS and Alsa asks to go with him. Before he realises what he is saying he agrees.

Promising Dela that he will return he points his sonic device at the huge sonic screwdriver. This rumbles into life and the Fortress disassembles into the lake. The three of them stand and laugh.

The TARDIS returns to Arcopolis. Twenty years have passed and the city is even more overgrown. A crowd gathers around them. Gar, a man now, and a white-haired Dela greet them from a crowd that gathers. Alsa shows them a small, charred fragment of metal, all that is left of the weapon. She says they stopped on an asteroid and dropped the cylinder into a plasma vent. The cylinder opened and something crawled out. Whatever it was couldn't survive in this universe. To Alsa this is only a day since she last saw these people.

The Doctor brings a cage containing a breeding pair of birds out of the TARDIS. He tells Dela that they are Kegronian Halcyons, renowned for their plumage and song. Gar tries to give him a necklace of polished glass but the Doctor tells him it won't work for him. Alsa takes it and puts it on. The glass is imprinted with memories, some from the Eyeless, some from the ghosts, including a lot of technological knowledge.