and scuttled on all fours around the Library's big glass and metal dome. He grabbed the rusty frame, hauled himself upright, and pulled out a knife. 'Come and get me, then,' he said. There was another roll of thunder. 'I don't have to,' said Vimes. 'I just have to wait.' At least until I get my breath back, he thought. 'Why're you picking on me? What'm I supposed to have done?'

'Couple of murders ring a bell?' said Vimes. If injured innocence was money, Carcer's face was his fortune. 'I don't know anything about-'

'I'm not up here to play games, Carcer. Knock it off.'

'You going to take me alive, your grace?'

'You know, I don't want to. But people think it's neater all round if I do.' There was a clattering of tiles away on the left, and a thud as a huge siege bow was rested on the ridge of a nearby roof. The head of Detritus rose behind it. 'Sorry about dat, Mister Vimes, hard to climb up in dat hail. Jus' stand back.'

'You're going to let it shoot me?' said Carcer. He tossed the knife away. 'An unarmed man?' "Trying to escape,' said Vimes. But this was starting to go bad. He could feel it. 'Me? I'm just standing here, haha.' And there it was. That bloody laugh, on top of that damn grin. It was never far away. 'Haha' didn't come close to doing it the injustice it deserved. It was more a sort of modulation to the voice, an irritatingly patronizing chortle that suggested that all this was somehow funny and you hadn't got the joke. Trouble was, you couldn't shoot someone for having an annoying laugh. And he was just standing there. If he ran, you could shoot him. Admittedly, it would be Detritus doing the shooting, and while with that bow it was technically possible to shoot to wound, the people you were wounding would probably be in the building next door. But Carcer was just waiting there, insulting the world by his existence. In fact he wasn't merely standing there now. In one movement he'd swung himself on to the lower slopes of the Library's dome. The glass panes - at least, the glass panes that had survived the freak hail - creaked in the iron framework. 'Stop right there!' Vimes bellowed. 'And come down!'

'Now where could I go?' said Carcer, grinning at him. 'I'm just waiting for you to arrest me, right? Hey, I can see your house from up here!' What's under the dome? thought Vimes. How high are the bookcases? There's other floors in the Library, aren't there? Like galleries? But you can definitely look up at the dome from the ground floor, right? If you were careful, could you swing on to a gallery from the edge of the dome? It'd be risky, but if a man knew he was going to swing anyway . . . Picking his way with care, he reached the edge of the dome. Carcer climbed up a little further. 'I warn you, Carcer-'

'Only high spirits, Mister Grace, haha! Can't blame a man for trying to enjoy his last few minutes of freedom, can you?'

'I can see your house from up here . . . Vimes hauled himself on to the dome. Carcer cheered. 'Well done, your Vimes!' he said, easing himself towards the top. 'Don't mess me about, Carcer. It'll go badly for you!'

'Badder than it's going to go anyway?' Carcer glanced down through a smashed pane. 'Long way down, Mister Vimes. I reckon a man'd die instantly falling all that way, wouldn't he?' Vimes glanced down, and Carcer leapt. It didn't go the way he'd planned. Vimes had been tensed for something like this. After a complicated moment, Carcer was lying on the iron latticework, one arm under him, the other outflung and being banged heavily on the metal by Vimes. The knife it had held skidded away down the dome. 'Gods, you must think I'm stupid,' Vimes growled. 'You wouldn't throw away a knife. Carcer, if you didn't have another one!' Vimes's face was close to the man's now, close enough to look into the eyes above that chirpy grin and watch the demons waving. 'You're hurting me, and that's not allowed!'

'Oh, I wouldn't want anything to happen to you, Carcer,' said Vimes. 'I want to see you in front of his lordship. I just want to hear you admit something for once. I just want to see that bloody cheeky grin wiped off your face. Sergeant Detritus!'

'Sah!' shouted the troll, from his distant ridge. 'Make a signal. I want people up here now. Me and Carcer are just going to stay nice and quiet here, so's he doesn't try any tricks.'

'Right, sir.' With another distant clatter of doomed tiles, the troll disappeared from view.

'You shouldn't have sent Captain Carrot away,' muttered Carcer. 'He doesn't like watchmen bullying innocent civilians-'

'It is true that he has yet to master some of the finer details of de facto street policing,' said Vimes, maintaining his grip. 'Anyway, I'm not hurting you, I'm protecting you. Wouldn't like you to fall all that way.' Thunder rumbled again. The sky wasn't just storm-black now. There were pinks and purples in the clouds, as though they were bruised. Vimes could see the clouds moving like snakes in a sack, to an endless sullen rumbling. He wondered if the wizards had been messing about with the weather. Something was happening to the air. It tasted of burned metal and flints. A weathercock on top of the dome began to spin round and round. 'I didn't think you was stupid, Mister Vimes 'What?' said Vimes, looking down suddenly. Carcer was smiling cheerfully. 'I said I didn't think you was stupid, Mister Vimes. I know a clever copper like you'd think I'd got two knives.'

'Yeah, right,' said Vimes. He could feel his hair trying to stand on end. Little blue caterpillars of light were crackling over the ironwork of the dome, and even over his armour. 'Mister Vimes?'

'What?' Vimes snapped. Smoke was rising from the weathercock's bearings. 'I got three knives, Mister Vimes,' said Carcer, bringing his arm up. The lightning struck. Windows blew out and iron gutters melted. Roofs lifted into the air and settled again. Buildings shook. But this storm had been blowing in from far across the plains, pushing the natural background magic ahead of it. It dumped it now, all in one go. They said afterwards that the bolt of lightning hit a clock-maker's shop in the Street of Cunning Artificers, stopping all the clocks at that instant. But that was nothing. In Baker Street a couple who had never met before became electrically attracted to one another and were forced to get married after two days for the sake of public decency. In the Assassins' Guild, the chief armourer became hugely, and since he was in the armoury at the time, tragically attractive to metal. Eggs fried in their baskets, apples roasted on the greengrocers' shelves. Candles lit themselves. Cartwheels exploded. And the ornate tin bath of the Archchancellor of Unseen University was lifted neatly off the floor, sizzled across his study and then flew off the balcony and on to the lawn in the octangle several storeys below, without spilling more than a cupful of suds.

Archchancellor Mustrum Ridcully paused with his long-handled scrubbing brush hovering halfway down his back, and stared around. Tiles smashed to the ground. Water boiled in the ornamental fountain near by. Ridcully ducked as a stuffed badger, the origin of which was never ascertained, flew across the lawn and smashed through a window. He winced as he was hit by a brief and inexplicable shower of small cogwheels, which pattered down all around him. He stared as half a dozen watchmen dashed into the octangle and headed up the steps to the Library. Then, gripping the sides of the bath, the Archchancellor stood up. Foaming water cascaded off him, as it would off some ancient leviathan erupting from the abyssal sea. 'Mister Stibbons!' he bellowed, his voice bouncing off the imposing walls, 'Where the is my hat?' He sat down again and waited. There were a few minutes of silence and then Ponder Stibbons, Head of Inadvisably Applied Magic and Praelector of Unseen University, came running out of the main door carrying Ridcully's pointy hat. The Archchancellor snatched at it and rammed it on his head. 'Very well,' he said, standing up again. 'Now, will care to tell m at the is going on? And why Old Tom ing repeatedly?'

' been a of magic, sir! I someone up the mechanism!' Ponder shouted, above the sound- destroying silences.* * Old Tom, the University's venerable clock, tolled not sounds but silences. They were not simply ordinary silences, but intervals of noise- absorbing non-sound that filled the world with loud soundlessness. There was a dying metallic noise from the big clock tower. Ponder and Ridcully waited a few moments, but the city stayed full of normal noise, like the collapse of masonry and distant screams. 'Right,' said Ridcully, as if grudgingly awarding the world a mark for trying. 'What was that all about, Stibbons? And why are there policemen in the Library?'

'Big magical storm, sir. Several thousand gigathaums. I believe the Watch is chasing a criminal.'

'Well, they can't just run in here without askin',' said Ridcully, stepping out of the bath and striding forward. 'What do we pay our taxes for, after all?'

'Er, we don't actually pay taxes, sir,' said Ponder, running after him. 'The system is that we promise to pay taxes if the city ever asks us to, provided the city promises never to ask us, sir. We make a voluntary-'

'Well, at least we have an arrangement, Stibbons.'

'Yes, sir. May I point out that you-'

'And that means they have to ask permission. The essential decencies must be maintained,' said Ridcully firmly. 'And I am the Master of this college!'

'On the subject of, er, decencies, sir, you are not in fact wearing-' Ridcully strode through the open doors of the Library. 'What is going on here?' he demanded. The watchmen turned, and stared. A large blob of foam, which up until that point had been performing sterling service in the cause of the essential decencies, slipped slowly to the floor. 'Well?' he snapped. 'Haven't you lot seen a wizard before?' A watchman snapped to attention and saluted. 'Captain Carrot, sir. We've, er, never seen so much of a wizard, sir.' Ridcully gave him the slow blank stare used by those with acute uptake- grasping deficiency. 'What's he talkin' about, Stibbons?' he said out of the corner of his mouth. 'You're, er, insufficiently dressed, sir.'

'What? I've got my hat on, haven't I?'

'Yes, sir-'

'Hat = wizard, wizard = hat. Everything else is frippery. Anyway, I'm sure we're all men of the world,' Ridcully added, looking around. For the first time he took in other details about the watchmen. 'And dwarfs of the world ... ah ... trolls of the world too, I see . . . and . . . women of the world too, I note . . . er . . .' The Archchancellor lapsed into a moment's silence, and then said, 'Mr Stibbons?'

'Yes, sir?'

'Would you be so kind as to run up to my rooms and fetch my robe?'

'Of course, sir.'

'And, in the meantime, please be so good as to lend me your hat. . .'

'But you do actually have your hat on, sir,' said Ponder. 'Quite so, quite so,' said Ridcully, slowly and carefully through his fixed grin. 'And now, Mister Stibbons, in addition, right now, I wish you, in fact, to lend, to me, your hat, please.'

'Oh,' said Ponder. 'Er . . . yes . . .'

A few minutes later a thoroughly clean and decent and clothed Archchancellor was standing in the very centre of the Library, staring up at the damaged dome, while beside him Ponder Stibbons - who for some reason had elected to continue to remain hatless, even though his hat had been handed back to him - stared glumly at some magical instruments. 'Nothing at all?' said Ridcully. 'Ook,' said the Librarian.* * Who was an orangutan, changed from his former human shape as a result of a long-forgotten magical accident. It was so forgotten, in fact, that now people were forgetting he was an orangutan. This might seem quite hard to do, given that even a small orangutan is quite capable of filling all immediately available space, but to the wizards and most of the citizens he was now just the Librarian, and that was that. In fact, if someone ever reported that there was an orangutan in the Library, the wizards would probably go and ask the Librarian if he'd seen it. 'You've searched everywhere?'