Finally Lord Vetinari said: 'Very well. I believe you're getting married at noon tomorrow.' His long fingers picked up the gilt-embossed invitation from the desk 'Yes. You can keep your badge, then. And have an honourable retirement. But I'm keeping the sword. And the Day Watch will be sent down to the Yard shortly to disarm your men. I'm standing the Night Watch down, Captain Vimes. In due course I might appoint another man in charge – at my leisure. Until then, you and your men can consider yourselves on leave.'

'The Day Watch? A bunch of—'

'I'm sorry?'

'Yes, sir.'

'One infraction, however, and the badge is mine. Remember.'

Cuddy opened his eyes.

'You're alive?' said Detritus.

The dwarf gingerly removed his helmet. There was a gouge in the rim, and his head ached.

'It looks like a mild skin abrasion,' said Detritus.

'A what? Ooooh.' Cuddy grimaced. 'What about you, anyway?' he said. There was something odd about the troll. It hadn't quite dawned on him what it was, but there was definitely something unfamiliar, quite apart from all the holes.

'I suppose the armour was some help,' said Detritus. He pulled at the straps of his breastplate. Five discs of slid out at around belt level. 'If it hadn't slowed down I'd be seriously abraded.'

'What's up with you? Why are you talking like that?'

'Lake what, pray?'

'What happened to the “me big troll” talk? No offence meant.'

'I'm not sure I understand.'

Cuddy shivered, and stamped his feet to keep warm.

'Let's get out of here.'

They trotted to the door. It was shut fast.

'Can you knock it down?'

'No. If this place wasn't troll proof, it'd be empty. Sorry.'

'Detritus?'

'Yes?'

Are you all right? Only there's steam coming off your head.'

'I do feel . . . er . . .'

Detritus blinked. There was a tinkle of falling ice. Odd things were happening in his skull.

Thoughts that normally ambulated sluggishly around his brain were suddenly springing into vibrant, coruscat-ing life. And there seemed to be more and more of them.

'My goodness,' he said, to no-one in particular.

This was a sufficiently un-troll-like comment that even Cuddy, whose extremities were already going numb, stared at him.

'I do believe,' said Detritus, 'that I am genuinely cogitating. How very interesting!'

'What do you mean?'

More ice cascaded off Detritus as he rubbed his head.

'Of course!' he said, holding up a giant finger. 'Superconductivity!'

'Wha'?'

'You see? Brain of impure silicon. Problem of heat dissipation. Daytime temperature too hot, processing speed slows down, weather gets hotter, brain stops completely, trolls turn to stone until nightfall, ie, colder-temperature,however,lowertemperatureenough,brain operatesfasterand—'

'I think I'm going to freeze to death soon,' said Cuddy.

Detritus looked around.

'There are small glazed apertures up there,' he said.

'Too hi' to rea', e'en if I st' on y'shoulders,' mumbled Cuddy, slumping down further.

'Ah, but my plan involves throwing something through them to attract help,' said Detritus.

'Wha' pla'?'

'I have in fact eventuated twenty-three but this one has a ninety-seven per cent chance of success,' said Detritus, beaming.

'Ha'nt got an'ting t'throw,' said Cuddy.

'I have,' said Detritus, scooping him up. 'Do not worry. I can compute your trajectory with astonishing precision. And then all you will need to do is fetch Captain Vimes or Carrot or someone.'

Cuddy's feeble protests described an arc through the freezing air and vanished along with the window glass.

Detritus sat down again. Life was so simple, when you really thought about it. And he was really thinking.

He was seventy-six per cent sure he was going to get at least seven degrees colder.

Mr Cut-Me-Own-Throat Dibbler, Purveyor, Merchant Venturer and all-round salesman, had thought long and hard about going into ethnic foodstuffs. But it was a natural career procession. The old sausage-in-a-bun trade had been falling off lately, while there were all these trolls and dwarfs around with money in their pockets or wherever it was trolls kept their money, and money in the possession of other people had always seemed to Throat to be against the proper natural order of things.

Dwarfs were easy enough to cater for. Rat-on-a-stick was simple enough, although it meant a general improvement in Dibbler's normal catering standards.

On the other hand, trolls were basically, when you got right down to it, no offence meant, speak as you find . . . basically, they were walking rocks.

He'd sought advice about troll food from Chryso-prase, who was also a troll, although you'd hardly know it any more, he'd been around humans so long he wore a suit now and, as he said, had learned all kindsa civilized things, like extortion, money-lending at 300 per cent interest per munf, and stuff like that. Chrysoprase might have been born in a cave above the snowline on some mountain somewhere, but five minutes in Ankh-Morpork and he'd fitted right in. Dibbler liked to think of Chrysoprase as a friend; you'd hate to think of him as an enemy.

Throat had chosen today to give his new approach a try. He pushed his hot food barrow through streets broad and narrow, crying:

'Sausages! Hot sausages! Inna bun! Meat pies! Get them while they're hot!'

This was by way of a warm up. The chances of a human eating anything off Dibbler's barrow unless it was stamped flat and pushed under the door after two weeks on a starvation diet was, by now, remote. He looked around conspiratorially – there were always trolls working in the docks – and took the cover off a fresh tray.

Now then, what was it? Oh, yes . . .

'Dolomitic conglomerates! Get chore dolomitic conglomerates heeyar! Manganese nodules! Manganese nodules! Get them while they're . . . uh . , . nodule-shaped.' He hesitated a bit, and then rallied. 'Pumice! Pumice! Tufa a dollar! Roast limestones—'

A few trolls wandered up to stare at him.

'You, sir, you look . . . hungry,' said Dibbler, grinning widely at the smallest troll. 'Why not try our shale on a bun? Mmm-mmm! Taste that alluvial deposit, know what I mean?'

C. M. O. T. Dibbler had a number of bad points, but species prejudice was not one of them. He liked anyone who had money, regardless of the colour and shape of the hand that was proffering it. For Dibbler believed in a world where a sapient creature could walk tall, breathe free, pursue life, liberty and happiness, and step out towards the bright new dawn. If they could be persuaded to gobble something off Dibbler's hot-food tray at the same time, this was all to the good.

The troll inspected the tray suspiciously, and lifted up a bun.

'Urrh, yuk,' he said, 'it's got all ammonites in it! Yuk!'

'Pardon?' said Dibbler.

'Dis shale,' said the troll, 'is stale.'

'Lovely and fresh! Just like mother used to hew!'

'Yeah, and there's bloody quartz all through dis granite,' said another troll, towering over Dibbler. 'Clogs the arteries, quartz.'

He slammed the rock back on the tray. The trolls ambled off, occasionally turning around to give Dibbler a suspicious look.

'Stale? Stale! How can it be stale? It's rockl' shouted Dibbler after them He shrugged. Oh, well. The hallmark of a good businessman was knowing when to cut your losses.

He closed the lid of the tray, and opened another one.

'Hole food! Hole food! Rat! Rat! Rat-onna-stick! Rat-in-a-bun! Get them while they're dead! Get chore—'

There was a crash of glass above him, and Lance-Constable Cuddy landed head first in the tray.

'There's no need to rush, plenty for everyone,' said Dibbler.

'Pull me out,' said Cuddy, in a muffled voice. 'Or pass me the ketchup.'

Dibbler hauled on the dwarf's boots. There was ice on them.

'Just come down the mountain, have you?'

'Where's the man with the key to this warehouse?'

'If you liked our rat, then why not try our fine selection of-'

Cuddy's axe appeared almost magically in his hand.

'I'll cut your knees off,' he said.

'GerhardtSockoftheButchers'Guildiswhoyouwant.'

'Right.'

' Nowpleasetaketheaxeaway.'

Cuddy's boots skidded on the cobbles as he hurried off.

Dibbler peered at the broken remains of the cart. His lips moved as he calculated.

'Here!' he shouted. 'You owe – hey, you owe me for three rats!'

Lord Vetinari had felt slightly ashamed when he watched the door close behind Captain Vimes. He couldn't work out why. Of course, it was hard on the man, but it was the only way . . .

He took a key from a cabinet by his desk and walked over to the wall. His hands touched a mark on the plaster that was apparently no different from a dozen other marks, but this one caused a section of wall to swing aside on well-oiled hinges.

No-one knew all the passages and tunnels hidden in the walls of the Palace; it was said that some of them went a lot further than that. And there were any amount of old cellars under the city. A man with a pick-axe and a sense of direction could go where he liked just by knocking down forgotten walls.

He walked down several narrow flights of steps and along a passage to a door, which he unlocked. It swung back on well-oiled hinges.

It was not, exactly, a dungeon; the room on the other side was quite airy and well lit by several large but high windows. It had a smell of wood shavings and glue.

'Look out!'

The Patrician ducked.

Something batlike clicked and whirred over his head, circled erratically in the middle of the room, and then flew apart into a dozen jerking pieces.

'Oh dear,' said a mild voice. 'Back to the drawing tablet. Good afternoon, your lordship.'

'Good afternoon, Leonard,' said the Patrician. 'What was that?'

'I call it a flapping-wing-flying-device,' said Leonard da Quirm, getting down off his launching stepladder. 'It works by gutta-percha strips twisted tightly together. But not very well, I'm afraid.'

Leonard of Quirm was not, in fact, all that old. He was one of those people who started looking venerable around the age of thirty, and would probably still look about the same at the age of ninety. He wasn't exactly bald, either. His head had just grown up through his hair, rising like a mighty rock dome through heavy forest.

Inspirations sleet through the universe continuously. Their destination, as if they cared, is the right mind in the place at the right time. They hit the right neuron, there's a chain reaction, and a little while later someone is blinking foolishly in the TV lights and wondering how the hell he came up with the idea of pre-sliced bread in the first place.

Leonard of Quirm knew about inspirations. One of his earliest inventions was an earthed metal nightcap, worn ini the hope that the damn things would stop leaving their white-hot trails across his tortured imagination. It seldom worked. He knew the shame of waking up to find the sheets covered with nocturnal sketches of unfamiliar siege engines and novel designs for apple-peeling machines.

The da Quirms had been quite rich and young Leonard had been to a great many schools, where he had absorbed a ragbag of information despite his habit of staring out of the window and sketching the flight of birds. Leonard was one of those unfortunate individuals whose fate it was to be fascinated by the world, the taste, shape and movement of it . . .

He fascinated Lord Vetinari as well, which is why he was still alive. Some things are so perfect of their type that they are hard to destroy. One of a kind is always special.

He was a model prisoner. Give him enough wood, wire, paint and above all give him paper and pencils, and he stayed put.