'Yeah,' said Rincewind, picking up a knife and testing its blade thoughtfully. 'Luters, I expect.'

He thrust the blade into the wall, twisted it, and stepped ack as a heavy stone fell out. He looked up, counting under his breath, and levered another stone from its socket.

'How did you do that?' said Twoflower.

'Just give me a leg up, will you?' said Rincewind. A moment later, his feet wedged into the holes he had created, he was making further steps halfway up the wall.

'It's been like this for centuries,' his voice floated down. 'Some of the stones haven't got any mOrtar. Secret entrance, see? Watch out below.'

Another stone cracked into the cobbles.

'Students made it long ago,' said Rincewind. 'Handy way in and out after lights out.'

'Ah,' said Twoflower, 'I understand. Over the wall and out to brightly-lit tavernas to drink and sing and recite poetry, yes?'

'Nearly right except for the singing and the poetry, yes,' said Rincewind. 'A couple of these spikes should be loose—' There was a clang.

'There's not much of a drop this side,' came his voice after a few seconds. 'Come on, then. If you're coming.'

And so it was that Rincewind, Twoflower and Bethan entered Unseen University.

Elsewhere on the campus—

The eight wizards inserted their keys and, with many a worried glance at one another, turned them. There was a faint little snicking sound as the lock slid open.

The Octavo was unchained. A faint octarine light played across its bindings.

Trymon reached out and picked it up, and none of the others objected. His arm tingled.

He turned towards the door.

'Now to the Great Hall, brothers,' he said, 'if I may lead the way —'

And there were no objections.

He reached the door with the book tucked under his rm. It felt hot, and somehow prickly.

At every step he expected a cry, a protest, and none came. He had to use every ounce of control to stop himself from laughing. It was easier than he could have imagined.

The others were halfway across the claustrophobic dungeon by the time he was through the door, and perhaps they had noticed something in the set of his shoulders, but it was too late because he had crossed the threshold, gripped the handle, slammed the door, turned the key, smiled the smile.

He walked easily back along the corridor, ignoring the enraged screams of the wizards who had just discovered how impossible it is to pass spells in a room built to be impervious to magic.

The Octavo squirmed, but Trymon held it tightly. Now he ran, putting out of his mind the horrible sensations under his arm as the book shape-changed into things hairy, skeletal and spiky. His hand went numb. The faint chittering noises he had been hearing grew in volume, and there were other sounds behind them – leering sounds, beckoning sounds, sounds made by the voices of unimaginable horrors that Trymon found it all too easy to imagine. As he ran across the Great Hall and up the main staircase the shadows began to move and reform and close in around him, and he also became aware that something was following, something with skittery legs moving obscenely fast. Ice formed on the walls. Doorways lunged at him as he barrelled past. Underfoot the stairs began to feel just like a tongue . . .

Not for nothing had Trymon spent long hours in the University's curious equivalent of a gymnasium, building up mental muscle. Don't trust the senses, he knew, because they can be deceived. The stairs are there, somewhere – will them to be there, summon them into being as you climb and, boy, you better get good at it. Because this isn't all imagination.

Great A'Tuin slowed.

With flippers the size of continents the skyturtle fought the pull of the star, and waited. There would not be long to wait . . .

Rincewind sidled into the Great Hall. There were a few torches burning, and it looked as though it had been set up for some sort of magical work. But the ceremonial candlesticks had been overturned, the complex octograms chalked on the floor were scuffed as if something had danced on them, and the air was full of a smell unpleasant even by Ankh-Morpork's broad standards. There was a hint of sulphur to it, but that underlay something worse. It smelt like the bottom of a pond.

There was a distant crash, and a lot of shouting.

'Looks like the gates have gone down,' said Rincewind.

'Let's get out of here,' said Bethan.

'The cellars are this way,' said Rincewind, and set off through an arch.

'Down there!'

'Yes. Would you rather stay here?'

He took a torch from its bracket on the wall and started down the steps.

After a few flights the walls stopped being panelled and were bare stone. Here and there heavy doors had been propped open.

'I heard something,' said Twoflower.

Rincewind listened. There did seem to be a noise coming from the depths below. It didn't sound frightening. It sounded like a lot of people hammering on a door and shouting 'Oi!'

'It's not those Things from the Dungeon Dimensions you were telling us about, is it?' said Bethan.

They don't swear like that,' said Rincewind. 'Come on.'

They hurried along the dripping passages, following the screamed curses and deep hacking coughs that were somehow reassuring; anything that wheezed like that, the listeners decided, couldn't possibly represent a danger.

At last they came to a door set in an alcove. It looked strong enough to hold back the sea. There was a tiny grille.

'Hey!' shouted Rincewind. It wasn't very useful, but he couldn't think of anything better.

There was a sudden silence. Then a voice from the other side of the door said, very slowly, Who is out there?'

Rincewind recognised that voice. It had jerked him from daydreams into terror on many a hot classroom afternoon, years before. It was Lemuel Panter, who had once made it his personal business to hammer the rudiments of scrying and summoning into young Rincewind's head. He remembered the eyes like gimlets in a piggy face and the voice saying 'And now Mister Rincewind will come out here and draw the relevant symbol on the board' and the million mile walk past the waiting class as he tried desperately to remember what the voice had been droning on about five minutes before. Even now his throat was going dry with terror and randomised guilt. The Dungeon Dimensions just weren't in it.

'Please sir, it's me, sir, Rincewind, sir,'he squeaked. He saw Twoflower and Bethan staring at him, and coughed, 'Yes,' he added, in as deep a voice as he could manage. That's who it is. Rincewind. Right.'

There was a susurration of whispers on the other side of the door.

'Rincewind?'

'Prince who?'

'I remember a boy who wasn't any—'

'The spell, remember?'

'Rincewind?'

There was a pause. Then the voice said, 'I suppose the key isn't in the lock, is it?'

'No,' said Rincewind.

'What did he say?'

'He said no.'

'Typical of the boy.'

'Um, who is in there?' said Rincewind.

'The Masters of Wizardry,' said the voice, haughtily.

'Why?'

There was another pause, and then a conference of embarrassed whispers.

'We, uh, got locked in,' said the voice, reluctantly.

'What, with the Octavo?'

Whisper, whisper.

'The Octavo, in fact, isn't in here, in fact,' said the voice slowly.

'Oh. But you are?' said Rincewind, as politely as possible while grinning like a necrophiliac in a morgue.

'That would appear to be the case.'

'Is there anything we can get you?' said Twoflower anxiously.

'You could try getting us out.'

'Could we pick the lock?' said Bethan.

'No use,' said Rincewind. 'Totally thief-proof.'

'I expect Cohen would have been able to,' said Bethan loyally. 'Wherever he's got to.'

'The Luggage would soon smash it down,' agreed Twoflower.

'Well, that's it then,' said Bethan. 'Let's get out into the fresh air. Fresher air, anyway.' She turned to walk away.

'Hang on, hang on,' said Rincewind. That's just typical, isn't it? Old Rincewind won't have any ideas, will he? Oh, no, he's just a makeweight, he is. Kick him as you pass. Don't rely on him, he's —'

'All right,' said Bethan. 'Let's hear it, then.'

'— a nonentity, a failure, just a – what?'

'How are you going to get the door open?' said Bethan.

Rincewind looked at her with his mouth open. Then he looked at the door. It really was very solid, and the lock had a smug air.

But he had got in, once, long ago. Rincewind the student had pushed at the door and it had swung open, and then a moment later the Spell had jumped into his mind and ruined his life.

'Look,' said a voice from behind the grille, as kindly as it could manage. 'Just go and find us a wizard, there's a good fellow.'

Rincewind took a deep breath.

'Stand back,' he rasped.

'What?'

'Find something to hide behind,' he barked, with his voice shaking only slightly. 'You too,' he said to Bethan and Twoflower.

'But you can't —'

'I mean it!'

'He means it,' said Twoflower. 'That little vein on the side of his forehead, you know, when it throbs like that, well —'

'Shut up!'

Rincewind raised one arm uncertainly and pointed it at the door.

There was total silence.

Oh gods, he thought, what happens now?

In the blackness at the back of his mind the Spell shifted uneasily.

Rincewind tried to get in tune or whatever with the metal of the lock. If he could sow discord amongst its atoms so that they flew apart —

Nothing happened.

He swallowed hard, and turned his attention to the wood. It was old and nearly fossilised, and probably wouldn't burn even if soaked in oil and dropped into a furnace. He tried anyway, explaining to the ancient molecules that they should try to jump up and down to keep warm —

In the strained silence of his own mind he glared at the Spell, which looked very sheepish.

He considered the air around the door itself, how it might best be twisted into weird shapes so that the door existed in another set of dimensions entirely.

The door sat there, defiantly solid.

Sweating, his mind beginning the endless walk up to 187 the blackboard in front of the grinning class, he turned desperately to the lock again. It must be made of little bits of metal, not very heavy —

From the grille came the faintest of sounds. It was the noise of wizards untensing themselves and shaking their heads.

Someone whispered, 'I told you—'

There was a tiny grinding noise, and a click.

Rincewind's face was a mask. Perspiration dripped off his chin.

There was another click, and the grinding of reluctant spindles. Trymon had oiled the lock, but the oil had been soaked up by the rust and dust of years, and the only way for a wizard to move something by magic, unless he can harness some external movement, is to use the leverage of his mind itself.

Rincewind was trying very hard to prevent his brain being pushed out of his ears.

The lock rattled. Metal rods flexed in pitted groves, gave in, pushed levers.

Levers clicked, notches engaged. There was a long drawn-out grinding noise that left Rincewind on his knees.

The door swung open on pained hinges. The wizards sidled out cautiously.

Twoflower and Bethan helped Rincewind to his feet. He stood grey-faced and swaying.

'Not bad,' said one of the wizards, looking closely at the lock. 'A little slow, perhaps.'

'Never mind that!' snapped Jiglad Wert. 'Did you three see anyone on the way down here?'

'No,' said Twoflower.

'Someone has stolen the Octavo.'

Rincewind's head jerked up. His eyes focussed.

'Who?'

'Trymon —'