Ponder had long been struck by the fact that the Librarian, an ape – at least generally an ape, although this evening he seemed to have settled on being a small table set with a red-furred tea service – was, well, so human shaped. In fact, so many things were pretty much the same shape. Nearly everything you met was really a sort of complicated tube with two eyes and four arms or legs or wings. Oh, or they were fish. Or insects. All right, spiders as well. And a few odd things like starfish and whelks. But still there was a remarkably unimaginative range of designs. Where were the six-armed, six-eyed monkeys pinwheeling through the jungle canopy?

Oh, yes, octopussies too, but that was the point, they were really only a kind of underwater spider...

Ponder had poked around among the University's more or less abandoned Museum of Quite Unusual Things, and noticed something rather odd. Whoever had designed the skeletons of creatures had even less imagination than whoever had done the outsides. At least the outside-designer had tried a few novelties in the spots, wool and stripes department, but the bone-builder had generally just put a skull on a ribcage, shoved a pelvis in further along, stuck on some arms and legs and had the rest of the day off. Some ribcages were longer, some legs were shorter, some hands became wings, but they all seemed to be based on one design, one size stretched or shrunk to fit all.

Not to his very great surprise, Ponder seemed to be the only one around who found this at all interesting. He'd point out to people that fish were amazingly fish-shaped, and they'd look at him as if he'd gone mad.

Palaeontology and archaeology and other skulduggery were not subjects that interested wizards. Things are buried for a reason, they considered. There's no point in wondering what it was. Don't go digging things up in case they won't let you bury them again.

The most coherent theory was one he recalled from his nurse when he was small. Monkeys, she'd averred, were bad little boys who hadn't come in when called, and seals were bad little boys who'd lazed around on the beach instead of attending to their lessons. She hadn't said that bird were bad little boys who'd gone too close to the cliff edge, and in any case jellyfish would be more likely, but Ponder couldn't help thinking that, harmlessly insane though the woman had been, she might have had just the glimmerings of a point...

He was spending most nights now watching Hex trawl the invisible writings for any hints. In theory, because of the nature of L-space, absolutely everything was available to him, but that only meant that it was more or less impossible to find whatever it was you were looking for, which is the purpose of computers.

Ponder Stibbons was one of those unfortunate people cursed with the belief that if only he found out enough things about the universe it would all. somehow, make sense. The goal is the Theory of Everything, but Ponder would settle for the Theory of Something and, late at night, when Hex appeared to be sulking, he despaired of even a Theory of Anything.

And it might have surprised Ponder to learn that the senior wizards had come to approve of Hex, despite all the comments on the lines of 'In my day we used to do our own thinking.' Wizardry was traditionally competitive, and, while UU was currently going through an extended period of peace and quiet, with none of the informal murders that had once made it such a terminally exciting place, a senior wizard always distrusted a young man who was going places since traditionally his route might be via your jugular.

Therefore there's something comforting in knowing that some of the best brains in the University, who a generation ago would be coming up with some really exciting plans involving trick floorboards and exploding wallpaper, were spending all night in the High Energy Magic Building, trying to teach Hex to sing 'Lydia the Tattooed Lady', exulting at getting a machine to do after six hours' work something that any human off the street would do for tuppence, then sending out for banana-and-sushi pizza and falling asleep at the keyboard. Their seniors called it technomancy, and slept a little easier in their beds in the knowledge that Ponder and his students weren't sleeping in theirs.

Ponder must have nodded off, because he was awakened just before 2 a.m. by a scream and realized he was face down in half of his supper. He pulled a piece of banana-flavoured mackerel off his cheek, left Hex quietly clicking through its routine and followed the noises.

The commotion led him to the hall in front of the big doors leading to the Library. The Bursar was lying on the floor, being fanned with the Senior Wrangler's hat.

'As far as we can gather, Archchancellor,' said the Dean, 'the poor chap couldn't sleep and came down for a book—'

Ponder looked at the Library doors. A big strip of black and yellow tape had been stuck across them, along with a sign saying: Danger, Do Notte Enter in Any Circumstances. It was now hanging off, and the doors were ajar. This was no surprise. Any true wizard, faced with a sign like 'Do not open this door. Really. We mean it. We're not kidding. Opening this door will mean the end of the universe,' would automatically open the door in order to see what all the fuss was about. This made signs rather a waste of time, but at least it meant that when you handed what was left of the wizard to his grieving relatives you could say, as they grasped the jar, 'We told him not to.'

There was silence from the darkness on the other side of the doorway.

Ridcully extended a finger and pushed one door slightly.

Behind it something made a fluttering noise and the doors were slammed shut. The wizards jumped back.

'Don't risk it, Archchancellor!' said the Chair of Indefinite Studies. 'I tried to go in earlier and the whole section of Critical Essays had gone critical!'

Blue light flickered under the doors.

Elsewhere, someone might have said, 'It's just books! Books aren't dangerous!' But even ordinary books are dangerous, and not only the ones like Make Gelignite the Professional Way. A man sits in some museum somewhere and writes a harmless book about political economy and suddenly thousands of people who haven't even read it are dying because the ones who did haven't got the joke. Knowledge is dangerous, which is why governments often clamp down on people who can think thoughts above a certain calibre.

And the Unseen University Library was a magical library, built on a very thin patch of space-time. There were books on distant shelves that hadn't been written yet, books that never would be written. At least, not here. It had a circumference of a few hundred yards, but there was no known limit to its radius.

And in a magical library the books leak, and learn from one another...

They've started attacking anyone who goes in,' moaned the Dean. 'No one can control them when the Librarian's not here!'

'But we're a university! We have to have a library!' said Ridcully. 'It adds tone. What sort of people would we be if we didn't go into the Library?'

'Students,' said the Senior Wrangler morosely.

'Hah, I remember when I was a student,' said the Lecturer in Recent Runes. 'Old "Bogeyboy" Swallett took us on an expedition to find the Lost Reading Room. Three weeks we were wandering around. Had to eat our own boots.'

'Did you find it?' said the Dean.

'No, but we found the remains of the previous year's expedition.'

'What did you do?'

'We ate their boots, too.'

From beyond the door came a flapping, as of leather covers.

There's some pretty vicious grimoires in there,' said the Senior Wrangler. They can take a man's arm right off.'

'Yes, but at least they don't know about doorhandles,' said the Dean.