There was a series of creaks as something heavy moved along the corridor outside and a troll opened the door.

'Yessir?'

'This is Corporal Littlebottom. Corporal Cheery Littlebottom, whose father was Jolly Littlebottom.

Give him his badge, swear him in, show him where everything is. Very good, Corporal?'

'I shall try to be a credit to the uniform, sir,' said Littlebottom.

'Good,' said Vimes briskly. He looked at Detritus. 'Incidentally, Sergeant, I've got a report here that a troll in uniform nailed one of Chrysoprase's henchmen to a wall by his ears last night. Know anything about that?'

The troll wrinkled its enormous forehead. 'Does it say anything 'bout him selling bags of Slab to troll kids?'

'No. It says he was going to read spiritual literature to his dear old mother,' said Vimes.

'Did Hardcore say he saw dis troll's badge?'

'No, but he says the troll threatened to ram it where the sun doesn't shine,' said Vimes.

Detritus nodded gravely. 'Dat's a long way to go just to ruin a good badge,' he said.

'By the way,' said Vimes, 'that was a lucky guess of yours, guessing that it was Hardcore.'

'It come to me in a flash, sir,' said Detritus. 'I fort: what bastard who sells Slab to kids deserves bein' nailed up by his ears, sir, and... bingo. Dis idea just formed in my head.'

'That's what I thought.'

Cheery Littlebottom looked from one impassive face to the other. The Watchmen's eyes never left each other's face, but the words seemed to come from a little distance, as though both of them were reading an invisible script.

Then Detritus shook his head slowly. 'Musta been a impostor, sir. 'S easy to get helmets like ours. None of my trolls'd do anything like dat. Dat would be police brutality, sir.'

'Glad to hear it. Just for the look of the thing, though, I want you to check the trolls' lockers. The Silicon Anti-Defamation League are on to this one.'

'Yes, sir. An' if I find out it was one of my trolls I will be down on dat troll like a ton of rectang'lar buildin' things, sir.'

'Fine. Well, off you go, Littlebottom. Detritus will look after you.'

Littlebottom hesitated. This was uncanny. The man hadn't mentioned axes, or gold. He hadn't even said anything like 'You can make it big in the Watch'. Littlebottom felt really unbalanced.

'Er... I did tell you my name, didn't I, sir?'

'Yes. Got it down here,' said Vimes. 'Cheery Littlebottom. Yes?'

'Er... yes. That's right. Well, thank you, sir.'

Vimes listened to them go down the passage. Then he carefully shut the door and put his coat over his head so that no one would hear him laughing.

'Cheery Littlebottom!'

Cheery ran after the troll called Detritus. The Watch House was beginning to fill up. And it was clear that the Watch dealt with all sorts of things, and that many of them involved shouting.

Two uniformed trolls were standing in front of Sergeant Colon's high desk, with a slightly smaller troll between them. This troll was wearing a downcast expression. It was also wearing a tutu and had a small pair of gauze wings glued to its back.

'—happen to know that trolls don't have any tradition of a Tooth Fairy,' Colon was saying. 'Especially not one called' - he looked down -'Clinkerbell. So how about it we just call it breaking and entering without a Thieves' Guild licence?'

'Is racial prejudice, not letting trolls have a Tooth Fairy,' Clinker bell muttered.

One of the troll guards upended a sack on the desk. Various items of silverware cascaded over the paperwork.

'And this is what you found under their pillows, was it?' said Colon.

'Bless dere little hearts,' said Clinkerbell.

At the next desk a tired dwarf was arguing with a vampire. 'Look,' he said, 'it's not murder. You're dead already, right?'

'He stuck them right in me!'

'Well, I've been down to interview the manager and he said it was an accident. He said he's got nothing against vampires at all. He says he was merely carrying three boxes of HB Eraser Tips and tripped over the edge of your cloak.'

'I don't see why I can't work where I like!'

'Yes, but... in a pencil factory?'

Detritus looked down at Littlebottom and grinned. 'Welcome to life in der big city, Little-bottom,' he said. 'Dat's an int'restin' name.'

'Is it?'

'Most dwarfs have names like Rockheaver or Stronginthearm.'

'Do they?'

Detritus was not one for the fine detail of relationships, but the edge in Littlebottom's voice got through to him. S a good name, though,' he said.

'What's Slab?' said Cheery.

'It are chloric ammonium an' radium mixed up. It give your head a tingle but melts troll brains. Big problem in der mountains and some buggers are makin' it here in der city and we tryin' to find how it get up dere, Mr Vimes is lettin' me run a' - Detritus concentrated - 'pub-lie a-ware-ness campaign tellin' people what happens to buggers who sells it to kids...' He waved a hand at a large and rather crudely done poster on the wall. It said:

Slab: Jus' say 'Aarrghaarrghpleeassennono-noUGH'.

He pushed open a door.

'Dis is der ole privy wot we don't use no more, you can use it for mixin' up stuff, it the only place we got now, you have to clean it up first 'cos it smells like a toilet in here.'

He opened another door. 'And this der locker room,' he said. 'You got your own peg and dat, and dere's dese panels for getting changed behind 'cos we knows you dwarfs is modest. It a good life if you don't weaken. Mr Vimes is okay but he a bit weird about some stuff, he keepin' on sayin' stufFlike dis city is a meltin' pot an' all der scum floats to der top, and stuff like dat. I'll give you your helmet an' badge in a minute but first' — he opened a rather larger locker on the other side of the room, which had 'DTRiTUS' painted on it - 'I got to go and hide dis hammer.'

Two figures hurried out of Ironcrust's Dwarf Bakery (T'Bread Wi' T'Edge'), threw themselves on to the cart and shouted at the driver to leave urgently.

He turned a pale face towards them and pointed to the road ahead.

There was a wolf there.

Not a usual kind of wolf. It had a blond coat, which around its ears was almost long enough to be a mane. And wolves did not normally sit calmly on their haunches in the middle of a street.

This one was growling. A long, low growl. It was the audible equivalent of a shortening fuse.

The horse was transfixed, too frightened to stay where it was but far too terrified to move.

One of the men carefully reached for a crossbow. The growl rose slightly. He even more carefully took his hand away. The growl subsided again.

'What is it?'

'It's a wolf!'

'In a city? What does it find to eat?'

'Oh, why did you have to ask that?'

'Good morning, gentlemen!' said Carrot, as he stopped leaning against the wall. 'Looks like the fog's rising again. Thieves' Guild licences, please?'

They turned. Carrot gave them a happy smile and nodded encouragingly.

One of the men patted his coat in a theatrical display of absentmindedness.

'Ah. Well. Er. Left the house in a bit of a hurry this morning, must've forgotten—'

'Section Two, Rule One of the Thieves' Guild Charter says that members must carry their cards on all professional occasions,' said Carrot.

'He's not even drawn his sword!' hissed the most stupid of the three-strong gang.

'He doesn't need to, he's got a loaded wolf.'

Someone was writing in the gloom, the scritching of their pen the only sound.

Until a door creaked open.