It’s six in the morning and Charles Dickens is still recovering from a long fit of vomiting yesterday. His stomach has been ailing, but he knows the bundle of parchments and accompanying documents that he’s chewing on are highly regarded as a rich source of food by the others here. He eats some more and concludes that the manuscripts are particularly marvellous. He’s interrupted by some nearby singing, which is coming from Martin Luther. He doesn’t recognise him at first after his recent metamorphosis because unlike him, Martin now has thoracic legs and is uniocular. They listen to a public announcement declaring the Reading Rooms to be open and that freshly baked cakes and buns will soon be available from the Buttery.

Elsewhere in the Depository, the Bibliotaph Myrtle Bunnage, apologises to Bernice for the mess and explains that they’ve had to let the cleaners go. She’s supposed to tidy her own study nowadays, but she always finds that at the end of a long day she’d rather just watch telly and eat nuts. In order to sit down, Bernice has to clear away a pile of birthday cards and Myrtle explains that all the robot employees have been programmed to send her one. She examines Bernice’s CV and is impressed by its straight edges, but then she apologises again and says they’d had to abolish the position she’s applied for. Bernice is shocked as the post has only just been advertised. Myrtle agrees it was horribly rude of them not to tell her earlier, but there have been cuts. She says they’re still interested in the documents Bernice had generously offered to donate to their collection, but Bernice is feeling slightly less generous now and says she might need to flog them for the money. The documents include some unpublished Sherlock Holmes stories including “The Cautionary Disappearance of Ludvig Cooray”, “The Adventure of the Diogenes Damsel” and some stuff about dogs that don’t bark in the night. She asks how much they’re willing to pay, but Myrtle says she’s not in a position to buy anything right now. She hands Bernice an envelope to act as compensation for her wasted journey, but it turns out just to be a voucher for a free cup of tea and a pastry in the Buttery.

In the Buttery, the robot cake-lady, Mrs Tishpishti, is looking after Peter. She’s teaching him how to bake and as he whisks the mixture, she tells him to imagine he‘s trapped down a sewer and slashing at a rat with a razor blade. Peter thinks it looks like snot, but is looking forward to licking the bowl. Mrs Tishpishti leaves to look after a customer, Panthea Vyne, who asks for some milk and says she’s running a bit late as they’ve found a new run of boxes containing lost works from the ‘Queen of Romance’ for her to catalogue. A despondent Bernice returns and says she didn’t get the job and is just as broke as she was this morning. Mrs Tishpishti sympathises but at least Bernice won’t starve as Peter had just finished making some meringues.

Panthea excitedly opens the boxes of books by Barbara Cartland, knowing she’s going to be the first person to read them in seven centuries. She finds the first draft of “Beauty or Brains?” and starts to read the contents into a Dictaphone, but she slowly realises there’s a faint voice in the distance somewhere repeating her words. Then the voice actually starts to predict the remainder of the text before she’s even got to it. She calls out to tell them they’re being silly, but there doesn’t seem to be anyone else in the room. One of the robot staff arrives and Panthea complains that someone’s preventing her from doing her work. She starts to read more of the book and they both listen as the tiny voice completes the paragraph again. The robot indicates that the voice is coming from inside one of the other boxes, but when they open it, there’s nothing there and whatever it was appears to have chewed its way out of the back.

Myrtle Bunnage welcomes the arrival of an Examiner from Earth Central. He asks her to be less casual and stick to formal protocols, adding that even his own wife uses his official title during office hours. She’s not sure what he’s looking for, but he invites her to offer any information she thinks he ought to know straight away as it’ll save her the bother later. She tells him the news is catastrophic and that they have a black hole in their finances. She admits that she’s been trying to conceal it, but to no avail. He immediately panics and suggests they evacuate the building, but she realises he thought she meant a real black hole. The truth is the Depository is completely broke, but there’s another problem too - something is destroying their collection…

Charles Dickens and Martin Luther take a break from eating and agree that it’s been a very satisfying meal. They’ve had hardly any visitors for two or three days, but just then they’re joined by another of their kind. The new arrival introduces himself as the author of “Atonina, or the Fall of Rome”. The others haven’t read it, but he’s brought with him various papers, manuscripts, letters and even a new novel, so he’ll really be able to eat his own words. He joins the others as they return to their hearty meal…

In the Buttery, Mrs Tishpishti tries to calm down the terrified Panthea Vyne with a hot cup of sweet tea. Panthea tells them she heard a tiny little voice, like an ant, and it was giving away the plot of the book she was reading. Bernice has never heard of Dame Barbara Cartland, even when Mrs Tishpishti and Panthea excitedly reel off a list of her best loved novels. They explain that she was the most prolific author Earth ever produced and it’s a miracle because nearly all her work survived the Dalek Wars (which is more than can be said for Jilly Cooper). Only the odd Barbara Cartland title is missing and it’s part of Panthea‘s job to track the remaining ones down. Some of them turned up unexpectedly in the Stacks recently, so Panthea went down to the lower Reading Room to catalogue them, and this is where she heard the voice coming from one of the box files. Bernice wonders if it wasn’t just one of the students having a joke, but Panthea plays back her Dictaphone recording and they agree it must be the voice of something very tiny indeed.

Myrtle takes Examiner Quick into the lower Reading Room and tells him it should contain “Beauty or Brains?”, but all they can see is a pile of shavings. She admits that it’s been happening every day - someone brings out a box of priceless papers and all they find is some residue which appears suspiciously like mouse droppings. It’s not random as only certain authors are being attacked. The correspondence of Martin Luther, father of the Protestant Reformation, was the first to go, but nobody’s touched Martin Luther King and he’s on the same shelf. Others to be affected are Barbara Cartland and Wilkie Collins. It reminds Myrtle of the time they lost part of the collection during the invasion and she thinks they should have moved to Hull because no one ever invades there. The Examiner takes a sample of the residue back to his ship for analysis and agrees to meet Myrtle back in her study in 83-96 minutes. After he leaves, Myrtle hears a tiny voice coming from the shadows. She identifies it as Martin Luther and warns him that she’s in charge, but Martin is not alone and he’s soon joined by the voices of Wilkie Collins and Charles Darwin.

It’s six o’clock and Mrs Tishpishti is preparing to re-open the Buttery for tea. She assigns duties to Peter while Bernice and Panthea help out with the tables. The cataloguer is still in shock from the sheer vandalism of the manuscripts. She tells Bernice she was brought up on Barbara Cartland by her grandfather and was even named after the heroine in “The Lady and the Highwayman”. She asks Bernice to join her down in the Reading Room to find out what’s going on, but Bernice says she doesn’t really do that sort of thing any more and is only interested in getting a proper job so she can look after Peter. Panthea pleads with her and suggests it’s more likely to help her get a job here than merely filling out an application form. Bernice reluctantly agrees to go with her on condition that Mrs Tishpishti is happy to do Peter’s bedtime. Panthea promises Peter she’ll play football with him tomorrow on the roof garden, then they can go cycling by the river and look at the edge of the atmosphere shield. Once they’re alone, Mrs Tishpishti encourages Peter to break the rules and have cake for dinner.

Examiner Quick returns to Myrtle Bunnage and tells her the lab results show that the contents of the Barbara Cartland box were eaten. He suspects there might also have been some unusual non-terrestrial quality to the typescript itself. Myrtle concludes from this that Barbara Cartland must have been an alien…

In the Reading Room, Panthea and Bernice examine a stack of boxes filled with what look like funny scraps of paper. As Panthea puts a few in her purse, they hear tiny voices coming from nearby. They open up one of the boxes and jump back in shock when they see a strange creature inside with at least six legs. The creature quotes a passage of literature back to them, then it races off across the room, closely followed by the two women…

Peter asks Mrs Tishpishti where she goes to bed, but she tells him she just herself in a cupboard and switches herself off while the servicing programmes check her for faults. As she’s staying up with him tonight, she’ll just plug herself in and recharge later. She admits that it puts a certain distance between her and other people who can go wherever they like. She starts combing his hair for crumbs, then makes up a bed for him above the oven and offers to read him a bedtime story to him. Unfortunately, she only knows Barbara Cartland novels, but they settle on the story “Ola and the Sea Wolf” as the title appeals to Peter…

Bernice and Panthea chase after the creature and eventually corner it behind a waste paper basket. Bernice asks it if it can understand what they say because although it’s talking to them, it’s not quite making sense. She coaxes the creature into sitting down with them and having a gentle, lady-like conversation, but before they can get anywhere, they’re interrupted by a loudspeaker announcement warning of un-ticketed visitors being detected in the Reading Room. Another of the creatures appears, but it too speaks in a strange disconnected manner, as if it’s quoting random sections from unrelated books. Security robots appear in the room and demand to see Bernice and Panthea’s authorisation cards. Meanwhile, unseen by the robots, the two creatures disappear under a nearby door. The women are ordered to leave, but the robots refuse to let them go through the nearest door as it leads to the Buttery which is closed at this time. Panthea tells Bernice there’s no other way of getting into the Buttery until it opens in the morning, which means Peter’s stuck in there with Mrs Tishpishti. As there’s nothing else they can do, they decide to go for a drink.

Myrtle Bunnage tells Examiner Quick that before she met him she imagined she’d be lobbying him to open his cheque book to deal with their preservation crisis, but now she realises even money can’t help them out of this situation. She says things have got out of hand and she thinks it requires a serious solution - the Depository has its own de-fumigation system for dealing with infestations such as parasites, vermin and other creepy-crawlies. All you have to do is press a big red button and cyanide gas floods through all the Stacks and the Reading Rooms…

Martin Luther rejoins Charles Darwin. He thinks he’s about to die, but Darwin reassures him he’s just becoming a mouthless pupa and tells him it’ll be a marvellous transformation. Luther bemoans his useless sluggish body and asks for it to be taken beneath the earth to become prey to worms. Then slowly he begins to change into a cocoon…

Panthea is becoming increasingly enthusiastic about the selection of cocktails on offer in the bar, but Bernice isn’t too keen on the prices and suggests a bottle of cheap fizz instead. Panthea is enjoying the experience and says she doesn’t get out as much as she should, adding that Mrs Tishpishti isn’t very mobile and there are a lot of stairs in this town. They examine the shredded remains of “Beauty or Brains?” from Panthea’s purse, but then the typescript has a very strange reaction to the wine and it catches alight and explodes before their very eyes. Bernice realises that whatever it is, it’s certainly not paper!

In the Buttery, Mrs Tishpishti accidentally wakes Peter up as she starts preparing her cheese scones for the morning rush. He points to some ‘things’ under the bell-jars and asks what they are, but she says she doesn’t know. She caught them scuttling across the floor last night and put them in the jars where they’d have enough air to breath and could eat one of her macaroons. Peter examines the creatures more closely and notes that one of them appears to be asleep, but then he’s shocked when the other one talks back to him. He thinks the creature is either a caterpillar or a bookworm, but it objects to such a vulgar description. The creature talks to them in the strange disconnected manner as before, but this time Mrs Tishpishti recognises the words. She gets Peter to bring down a book from the shelf and she shows him the section where those exact words appear. The creature continues quoting lengthy passages from the text and Mrs Tishpishti reveals that he’s reading from Barbara Cartland’s “Etiquette for Love and Romance”. Just then, Bernice and Panthea return and explain that they got locked out so they had to spend all night in a bar. They stop in their tracks when they see the creature in the jar quoting further sections from the book…

Martin Luther emerges from his cocoon and is greeted by Charles Darwin who congratulates him on a marvellous transformation. He now has straightened and elongated mandibles and has six legs, a pair of antennae and singular eyes. He’s now a very different creature entirely.

Peter teases the creature by continually reading out random sections from the book and waiting for the word-perfect response. Bernice tells her son it’s not a toy for him to play with, but Mrs Tishpishti thinks the creature might actually be enjoying it. Panthea asks the creature what they should call it and it tells them its name is Barbara. Excitedly, she asks Barbara to read her the section from “Beauty or Brains?” containing the Tibetan monks and she confirms that the text fits perfectly with what they know from the synopsis. Bernice wonders how the grubs have learnt to talk and read, and Mrs Tishpishti suggests it might have been something they ate. That makes perfect sense to Bernice - the grubs eat the manuscripts and typescripts and then gain the ability to speak the words they’ve swallowed. To Bernice’s horror, she discovers Peter has tested the experiment by placing the second grub over a copy of her diary. True to form, the grub then starts speaking like Bernice and quoting some of her most intimate and private thoughts.

Examiner Quick finds Myrtle having breakfast and tells her she has full clearance to use the cyanide gas to fumigate the Depository. She can’t wait to finish her coffee and start gassing the little blighters into next week! The button to control the gas is hidden beneath her pile of birthday cards and as the Examiner starts clearing them away, he notices they’re all from the robot staff - and as they‘re robots they’ve all chosen exactly the same card. Myrtle asks if he’s found any from real organic people, but the only one he finds is from her mother and she admits that it was actually sent by her nurses.

Bernice is deeply embarrassed when the grub reads out more from her diary and Mrs Tishpishti wonders if she ever intended it to be published. Panthea realises from what she’s heard that Bernice is a bit of an expert in creatures and monsters, which means they now have access to one of the grubs with the right sort of vocabulary. If you ask Barbara Cartland about aliens, you’ll get a garbled response from someone who doesn’t understand the question because the words just aren’t there. However, if you ask Bernice Summerfield about aliens, you’ll get someone who actually knows what they’re talking about. Bernice agrees to ask the creature some questions, but in order to prevent it revealing anything too personal, she decides to limit it to yes and no answers. She begins by asking if it’s true that alien bookworms have found their way into the Reading Rooms and are munching their way through the literary history of Earth. The answer is yes. Further questioning reveals that the aliens haven’t always been able to talk, but they were affected by some kind of extra-terrestrial influence. The conversation is still a bit garbled and confused, so Peter suggests they write down the words they need and let the creature eat them, thereby adding them to its vocabulary. They chose some key words, including everybody’s names and the words Depository, worm, meringue (that was Peter’s choice), evil master plan, shelves, dust, cataloguing, manuscript, typescript and robots etc. Once that’s done, they sit back and wait for the creature to have its dinner.

Charles Darwin is ecstatic at discovering his partner has turned into a new species, of which he’s the only specimen known to exist. He also reveals that Martin Luther has become impregnated and is now engorged with larvae, although he’s doubtful they’ll ever hatch. Darwin proposes notifying the president of the Royal Society, but so engrossed are they in the subsequent debate they fail to hear another public announcement, warning that a fumigation of the Depository is about to begin and organic lifeforms have one hour to leave the premises.

The group in the Buttery have heard the announcement and Peter wants to go back to their spaceship, but Mrs Tishpishti promises everyone they’ll be quite safe here. Bernice isn’t entirely reassured by her comments and says the questioning of the grub isn’t going as well as she’d hoped anyway. The grub objects to her criticism and says it isn’t their fault people are using words they don’t understand. Mrs Tishpishti agrees and sympathises with the loneliness of the creatures as they’re the only ones of their kind. She adds that if the fumigation goes ahead, the species will be wiped out before they’ve had a chance to live. They try again and the grub tells them the creatures were all hatched together in the box file containing the typescript “Beauty or Brains?” There are only two other creatures down in the Reading Rooms. They’re both alone and soon the cyanide will come gushing down and kill them. Bernice says they need to convince the Bibliotaph to turn off the gas, but Mrs Tishpishti thinks they might be too late. She suggests some of them get down to the Reading Room to rescue the creatures while she visits Myrtle Bunnage. She knows the robots won’t let her carry an insect into the Bibliotaph’s office while there’s a fumigation going on, but fortunately she has a very good place to hide it. It’s Myrtle’s birthday today and Mrs Tishpishti has already baked her a cake…

Slowly, the cyanide gas pours through the ventilation shafts and begins to fill up the corridors on some of the upper levels. A public announcement warns those in the Depository that it will shortly commence fumigating the lower levels too and all organic lifeforms should evacuate the premises. Myrtle tells the Examiner that she thinks the lower levels are where the problem is. They notice there are people outside the Bibliotaph’s study - it’s a robot in female form and what appears to be a little dog, both of them singing “Happy Birthday” to Myrtle and carrying a cake with candles.

In the lower levels, Bernice is certain she can smell gas, but Panthea tells her it’s just her imagination and the fumigation won‘t have reached here yet. Panthea hears singing and Bernice is just about to tell her it’s only in her imagination when she hears it too. The worm known as Bernice recognises the singer, but it doesn’t have the words to tell them its name.

Myrtle invites Mrs Tishpishti and Peter in, but the robot cook tells her she can’t come any further inside as her flex is at its limit and she’ll pull the plug out of the socket if she tries. They tell her they’ve brought her a cake and she gratefully takes it and asks the Examiner to put it on the table. Mrs Tishpishti then says they’ve also come to ask her to stop the fumigation as a little family of creatures has been born down there. She asks Dame Barbara to jump out of the cake, but Peter has to give it a bit of a shake as the creature seems to have fallen asleep. To their surprise, they find the cake is empty! When they try to explain that there was a talking worm inside the cake, Myrtle becomes angry and orders them to leave.

Bernice introduces herself, Panthea and the worm known as Bernice to the singing worm who, in turn, introduces himself as Charles Darwin and his partner as Martin Luther. Panthea notices that Martin looks pregnant and Charles confirms that he’s about to produce thousands or even millions of babies. In answer to Bernice’s next question, he says it will only take the babies half an hour to eat their way through the entire Depository collection. In order to hold off the birth as long as possible, they persuade Martin to take a rest, but when Martin starts coughing they realise he must have got the first whiff of the cyanide gas. It’s time to get out of here and Bernice suggests carrying the worms in a box file. Unfortunately it’s too late and they hear the doors closing and locking behind them automatically.

Myrtle finishes sealing off the lower levels and confirms that the upper Reading Room is now almost completely sterilised. The Examiner wants to start on the cake and break open the champagne, but then they hear a tiny voice coming from inside a nearby filing cabinet. They open it to reveal the talking bookworm, which has been eating its way through Myrtle’s private correspondence. Then, to Myrtle’s deep embarrassment, it starts reading out the contents. It reveals that she recently put in an order for four specimens of a species known to be voracious consumers of paper products to be delivered in a plain brown wrapper. The Examiner asks the worm who put him in the Depository and it tells him it was the Bibliotaph. It’s now obvious that she arranged the whole thing herself in order to give the impression the Depository was under threat so that she could get more funding. The worm confirms this and the furious Myrtle squashes it under a heavy volume. She tells the Examiner that she thought they were just normal bookworms and she had no idea the creatures were going to mutate after nibbling on alien paper. Unfortunately she also had no idea that the filing robots had made duplicates of all her correspondence. Just then, the wall smashes open and Mrs Tishpishti bursts through the hole, telling Myrtle she has a lot of explaining to do. Peter crawls through and threatens to bite the Examiner and Myrtle unless they switch off the gas. The Examiner points out that the whole collection is under threat of being eaten, but Peter says it’s Myrtle’s fault and that his mum is still down there. Myrtle reveals that the system is automatic and there’s nothing she can do - no one is going to get out of there alive…

In the Reading Room, Bernice notices that all the vents are down one side of the room, so she suggests they all move as far away as they can. The worms agree to be carried and Bernice asks Martin to sing them something to keep their spirits up while they buy themselves some more time.

Mrs Tishpishti can’t move any further into the office, so all she can do is make idle threats towards Myrtle. The Examiner asks if there’s any way to reverse the fumigation process, but Myrtle says they’d need to chuck a hand grenade inside the gas pump. He demands to know what possessed her to do all this and she tells him Earth Central slashed their budget in half and if it wasn’t for the profits from the Buttery, they’d have had to close down months ago. She tells Peter he can still talk to the people down below if that’ll help, and he accepts her offer, but warns her that he’s still going to rip her legs off once this is all over.

Bernice responds to Myrtle’s call and learns that they can’t turn the gas off. Peter comes on line and she apologises to him for being such a bad mother. Suddenly Panthea realises the paper on which the book “Beauty or Brains?” was written will form the perfect explosive as it’s highly reactive in the presence of cheap white wine. Bernice remembers the incident in the bar and tries to pass on the message to Peter and Miss Bunnage, but the line has gone dead. The group starts coughing and they can taste the poisonous gas at the backs of their throats. They can’t have long left now. Panthea says at least if they die, the collection will be safe, but Bernice points out that if the worms die it’ll mean the end of all the correspondence from Charles Darwin and Martin Luther. They look for some means of protecting the worms from the gas, but they seem to have run out of ideas. Then, to Bernice’s surprise, Panthea picks up the three worms and one by one she puts them in her mouth and swallows them whole. She assures Bernice this wasn’t an act of genocide, but of preservation. Then she starts to feel sick and says it’s not from the cyanide gas…

The Examiner tells Myrtle she’s going to need a new desk (or more likely her successor will) as the few remaining pellets of Barbara Cartland’s alien note paper and the bottle of corner shop wine has seen it completely destroyed, together with the equipment controlling the gas. Peter asks about his mum and Myrtle calls her again, but there’s no response and she tells him it’s too late. Just then they hear Panthea singing in the strange alien voice of the worms. Bernice comes on line and assures Peter that everyone is alright. Panthea says she’s singing because she’s glad to be alive and she asks Mrs Tishpishti to put something in the oven as they’re on their way up!