Paradise Towers was the second story of Season 24 of Doctor Who. After a much-publicized falling out with Eric Saward, John Nathan-Turner was keen to find a writer who hadn’t worked on the show before. At the BBC’s script unit, he met Stephen Wyatt and asked him to submit a script for Doctor Who. At first the script lacked a traditional “monster”. The robotic Cleaners were added to the script to fulfill this role.
The last remaining Yellow Kang hides from the jeers of the other Kangs in a corridor, while the voices of her pursuers announce they have given up looking. Relieved, she turns to find something bearing down on her and screams. In the TARDIS, Mel looks longingly at the swimming pool displayed on the TARDIS scanner. They’ve arrived at Paradise Towers and Mel is looking forward to taking a dip. However, upon leaving the TARDIS, they find the place in disarray. The surfaces are filthy and rats scuttle around underfoot.
Caretaker 345/12, subsection 3 reports in to the Chief Caretaker, telling him he has found evidence of “wallscrawlers” on Potassium Street. As he continues his inspection, he finds a bloodied rag. Meanwhile, the Doctor and Mel find themselves threatened by a group of teenage girls calling themselves the Red Kangs. The Doctor placates them and they take a liking to him. Two of their number introduce themselves as Fire Escape and Bin Liner. They tell the Doctor they are rivals of the Blue Kangs and the Yellow Kangs, though only one of the latter is still alive.
A Blue Kang is following Caretaker 345/12, subsection 3 and uses a telephone to report that the Yellow Kangs are no more. After she leaves, a robot drives past with the leg of the last Yellow Kang sticking out of a rubbish container behind it. Back with the Red Kangs, the Doctor is asking questions. He finds that there are three types of people present in Paradise Towers: the Kangs, the old ones and the Caretakers. There seems to be more, but before Fire Escape can tell the Doctor of this group, Bin Liner gestures to her with a warning to keep silent regarding such things. With that they take the Doctor and Mel captive, having become interested in them after hearing their conversation about “the pool in the sky”.
Caretaker 345/12, subsection 3 finds himself facing one of the robots, with a second sneaking up behind him. He gets through to the chief, who tells him not to panic. One of the robot grabs him with a mechanical claw and kills him. The Caretaker watches on a screen as the robot takes the body away. He puts out a message for all Caretakers to seize every “red wallscrawler” in Fountain of Happiness Square. As the Red Kangs are taking Mel and the Doctor to a new location, the Caretakers move in. The group flees but the Doctor falls and is taken prisoner.
Separated from the Doctor and the Red Kangs, Mel comes across Tilda and her friend Tabby and is welcomed into their home. There are large bones on the table which are tidied away before they let Mel enter the room. Mel asks them what group they belong to and they tell her they’re Rezzies. They ply Mel with tea and cakes and invite her to dine.
The Doctor is being escorted by the Caretakers, including the Deputy Chief Caretaker, who allow him a short rest. He finds a “wallscrawl” depicting a Kang being attacked by a mechanical claw, with other mechanical objects surrounding this centerpiece. The Deputy shrugs it off as made-up imagery. One of the robots turns the corner as they chat and the Doctor identifies it as “some sort of robotic Cleaner”. As it readies its claw, they run away from it.
Back in Tilda and Tabby’s house, Mel is encouraged to stay awhile and eat to her heart’s content. Just as Tabby comments on the peacefulness of her home, the door is broken open and a man steps in, asking if Mel is either in or causing trouble. When he finds she is not, he introduces himself as Pex, telling her he “puts the world of Paradise Towers to rights”. Mel stands amazed at his immodesty. Elsewhere, the Doctor and his Caretaker accompaniment escape the Cleaner by taking a lift. Mel decides to leave Tilda and Tabby. Once outside, Pex tells her he will be her guide and help her find the Doctor. They come across some Blue Kangs engaged in worship. Meanwhile, the Doctor is brought before the Chief Caretaker who takes him for the original architect of Paradise Towers. The Deputy asks what is to be done with him and the Chief orders that the Doctor should be killed.
The Doctor tries to convince the Chief that he is not the “Great Architect”, but to no avail. The Chief orders his deputy to organise the execution. He gets a phone call from Caretaker 579/14, subsection 8, about the death of 345/12, subsection 3, and is required elsewhere. Until his return, the sentence is postponed. Elsewhere, Mel and Pex are still looking for the Doctor, and the Red Kangs find one of their number, No Exit, has been killed by the Cleaners.
The Deputy and another Caretaker are guarding the Doctor. He asks to see the rule book by which they run their lives and they oblige, treating it as his last request. Pretending he is reading rules from the book, the Doctor tells them to step away from him, close their eyes and put their hands on their heads. They do so and he takes the key card from the Deputy and escapes. Mel and Pex narrowly miss the Doctor. They find themselves back at the Fountain of Happiness Square. Mel asks Pex who he really is and he replies he had power invested in him by those he cannot name. As they move out of the square, they are followed by the Blue Kangs.
The Doctor comes across a wallscrawl while looking for Mel, takes out pen and paper and makes notes. Elsewhere, the Chief Caretaker is reassuring his team. He tries to quell any fears they have that the Caretakers are responsible. In their home, Tabby and Tilda are visited by Maddy, who tells them about the death of yet another Caretaker. She tells them that people cannot simply be disappearing and they agree, covering up their dinner.
Meanwhile, the Doctor comes across a telephone and breaks it. Money floods out. As he collects it in his hat, two Cleaners move in on him and he is forced down a hole. He wakes to find himself in the Red Kangs’ “brainquarters”. He confronts them about the Cleaners, but they know less than he, nor do they know what the creature their own wallscrawls depict is. The Doctor tries to use another phone, but it is not in use. He turns the cabinet attached to it around to reveal that it is a vending machine. He buys a can of Fizzade and shares it out among the Kangs.
The Chief Caretaker visits the creature. He refers to it as “my pet” and himself as its “daddy”. He asks the creature if it enjoyed its Caretaker snack and asks it who else has been feeding it. It replies that it is hungry. The Chief leaves, promising to feed it the Great Architect. Meanwhile, Mel and Pex find themselves prisoners of the Blue Kangs. Mel asks them if they know who Pex is and they tell her he’s the “musclebrain”, an in between — a term for those who are middle aged — who went with the Kangs by hiding aboard their ship, rather than fight in a war with all the other in betweens. Mel is allowed to leave. The Kangs call Pex a “scaredy-cat”.
The Chief declares it is time to seek the Great Architect and teach the Kangs a lesson for their recent defiance of Caretaker authority. Elsewhere, Mel finds herself back in Tilda and Tabby’s company when she is invited in for tea.
In their brain quarters, the Red Kangs are all drinking Fizzade now. The Doctor tries to side with them. However, an alarm blares and Bin Liner warns the Caretakers are moving in. On the other side of the door, the Caretakers begin to break it down. Back in their house, Tabby and Tilda are having crumpets with Mel, but this time, they have no intention of letting her go. They throw a net over Mel and Tabby brandishes a toasting fork at her throat.
The Doctor buys the Red Kangs time and encourages them to make their escape. Meanwhile, Mel warns Tabby that there is something wrong with the waste disposal unit. As she inspects it, a claw bursts out of it, grabs Tabby and pulls her through. Tilda blames Mel and throws a knife at her. Pex bursts through the door and Tilda runs to get a knife, but as she does so, the claw again emerges and pulls her through too. In the corridor, a cleaner drives past with Tilda’s foot sticking out of it.
The Caretakers break down the door to the Red Kang brain quarters to capture the Doctor. They find that he is the only one there. Mel is still trying to get to the “pool in the sky” — as it is known locally — where she arranged to meet the Doctor. Pex warns her that only the “un-alive” go there but deems it his duty to accompany her. The Doctor is brought before the Chief Caretaker, who deems it necessary for them to have a chat. The Deputy queries his leader as to the recent Caretaker fatalities, breaking several regulations and resulting in him being sent out of the room. The Chief tells the Doctor the “Great Architect” disappeared under mysterious circumstances soon after the completion of Paradise Towers. News of Tilda and Tabby’s deaths draws the Chief away and he leaves the Deputy to once again guard the Doctor.
Elsewhere, Mel and Pex enter a lift but find themselves victims of the cleaners who are pressing the buttons all up the shaft so that they are constantly moving and stuck in the lift. Bin Liner and Fire Escape break into the Chief’s office and tie up all the guards. The Doctor is free to leave. In Tilda and Tabby’s flat, the Chief is interviewing Maddy. He tells her there is no cause for alarm and encourages her to keep news of the incident quiet. She does not want to do so, but the Chief offers her the flat — which is much larger than hers — and she agrees to say nothing.
In the lift, Mel and Pex are stuck moving up and down between floors 173 and 174. Pex tries to fix the controls, but only causes the lift to quickly descend. They find themselves in the basement and hear a voice saying, “Soon, soon I shall be free”. In the Red Kang brain quarters, the Doctor is watching an information video about Kroagnon, the “Great Architect”. He tells the Kangs of Miracle City, a place built by Kroagnon and from which he refused to move out, or let anyone in. Eventually he was forced out and those who moved in he killed. However, nothing could be proven and so he walked free.
Pex gets the lift working again, and they start ascending. The Chief finds himself facing cleaner 479, who forces him to follow. At the brain quarters, the Doctor convinces the Red Kangs they must go the basement. The Blue Kangs burst in and proclaim victory over the Reds. The Doctor tries to convince them there is no time for games and they must all work together. Mel and Pex arrive at Floor 304 to find a serene, clean area of Paradise Towers greeting them. Mel finds the pool and settles down to rest in preparation for her swim, despite Pex thinking the water is dangerous. For once, his thoughts are correct. In the water, a giant, yellow, mechanical crab-like cleaner lurks below the surface and sights Mel on the edge.
The Chief is brought before “his pet” by a cleaner and asks him why he has been killing so many people. He replies that he needed a body to live in, but the ones the cleaners brought were not satisfactory. Behind the Chief, the Doctor, Bin Liner, Fire Escape and Drinking Fountain are sneaking up on them. The Chief is forced into a container as the creature declares itself as Kroagnon. The Doctor and his friends attack, but a cleaner grabs the Doctor with its claw and begins to throttle him.
The Kangs pull the Doctor free. They all flee. The container the Chief was placed in rises, leaving a silver-clothed Chief in its wake. Kroagnon has taken his body and reveals he tried to stop the use of Paradise Towers, leading to his imprisonment. He declares that, with the cleaners, he will destroy everyone in the Towers. The Doctor and the Kangs stop to rest with the immediate danger gone. He thinks the parents of Paradise Towers’ current inhabitants must have imprisoned Kroagnon, but he devised a means to perform corpo-electroscopy – a way to transplant his brain to a host body.
On Floor 304, Mel is swimming. She encourages Pex to join her but he just sits at the side. Suddenly, the water-bound cleaner surfaces and attacks Mel. In the Red Kang brain quarters, the Blues and the Reds have gathered. They wait for the Fire Escape’s arrival and plan to head for the “pool in the sky”. Back in the pool, Mel urges Pex to help her. She gets into the shallows and, borrowing Pex’s gun, shoots the cleaner. It sinks below the surface, its casing blown open. In the Chief’s office, the Deputy puts out Regulation ZZZ- an order for Caretakers to act with extreme caution and return to base.
Downstairs, Kroagnon leads a cleaner through the corridors as it spurts out jets of poisonous gas. A nearby Caretaker falls and dies and Kroagnon decides to return later to collect the “rubbish”. Meanwhile, the Doctor and the Kangs join Mel and Pex on Floor 304. The Kangs start taunting Pex again and he moves to leave, but his way is blocked by three Rezzies – including Maddy – who propose an alliance.
Kroagnon enters the Chief’s office and confronts the Deputy. Realizing that he is no longer the Chief Caretaker, the Deputy runs away. After some discussion, the Kangs agree to work with the (apologetic) Rezzies and Pex. They claim they will never work with the Caretakers, but, as they do so, the Deputy arrives and joins their alliance. In the Chief Caretaker’s office, Kroagnon is marking off floors that have been gassed. He notes that everyone will head to Floor 304 and he will gas each floor on the way up.
On Floor 304, the Deputy reveals that on Floor 245, Sodium Street, corridor 75, there is a secret emergency supply of explosives kept for pests going out of control. They decide to use this to set a trap for Kroagnon. The Rezzies plan to slow the cleaners with the table cloths they make, while the Kangs destroy them with explosives and the arrow guns they carry. Back in the Chief’s office, Kroagnon is still marking off floors as they are gassed. He decides to check what is going on in “the pool zone”, but finds that the surveillance has been prevented by “the Great Architect”.
The Doctor outlines his plan to capture Kroagnon: he will offer to meet their enemy. Someone will lead Kroagnon to him, where he will be trapped. Pex offers to do this, to the amusement of the Kangs. In the Chief’s office, Kroagnon gets a message from the Doctor who criticizes his work as an architect. In a corridor, a combined Rezzie and Kang effort sees a cleaner destroyed. On Floor 304, the Kangs give Pex gifts as he prepares to leave and he gives Mel his gun.
Pex goes to the Chief’s office and uses a video screen to communicate with Kroagnon. He agrees to accompany Pex to the Doctor and they begin to make their way through the corridors. However, contrary to the Doctor’s order to travel slowly, Pex is fearful of Kroagnon, so they make haste.
Soon they meet the Doctor and begin to converse. The Doctor tries to push Kroagnon through a door, but cannot move him. Pex grabs a stick of explosive, pushes the Doctor out of the way and pulls Kroagnon and himself through the doorway. Both are killed in the explosion.
The Kangs, Rezzie and Caretakers are holding a ceremony for Pex. They honor his bravery and the Doctor comments that he helped bring them all together. As a parting gift, the Kangs give the Doctor a scarf with a red side and a blue side – making him an honorary Kang. Mel and the Doctor return to the TARDIS and it de-materializes. Behind it, some wallscrawl says “Pex lives”.