`How do you know all this?' said Vimes.

`Because I'm magical,' said the voice from the hood.

`Oh, well, if that's the way you're-' Vimes began.

`Patience, commander,' said Mr Shine. `I just ... simplified. Accept, instead, that I am very ... smart. I have an analytical mind. I've studied the histories and lore of my hereditary enemy. I have friends who are dwarfs. Quite knowledgeable dwarfs. Quite ... powerful dwarfs, who wish for an end to this stupid feud as much as I do. And I have a love of games and puzzles. The Codex was not a terrible challenge.'

`If it's going to help me find the murderers of those dwarfs in the mine then you should tell me what you know!'

`Why trust what I say? I am a troll, I'm partisan, I might wish to direct your thoughts down the wrong path.'

`Maybe you have already!' said Vimes hotly. He knew he was making a fool of himself; it only made him angrier.

`Good, that's the spirit!' said Mr Shine. `Test all that I've told you! Where would we be if Commander Vimes relied on magic, eh? No, the secret of Koom Valley must be found by observation and questioning and facts, facts, facts. Possibly I'm helping you find them a little quicker than you might otherwise do. You just have to

think about what you know, commander. And, in the meantime, shall we play a little game?'

Mr Shine picked up a box by his chair and upended it over the table.

`This is Thud, Mister Vimes,' he said, as little stone figures bounced over the board. `Dwarfs versus trolls. Eight trolls and thirty-two dwarfs, forever fighting their little battles on a cardboard Koom Valley.' He began to place the pieces, black-gloved hands moving with un-trollish speed.

Vimes pushed back his chair. `Nice to meet you, Mr Shine, but all you are giving me is riddles and-'

`Sit down, commander.' The quiet voice had a schoolteacher harmonic to it that folded Vimes's legs under him. `Good,' said Mr Shine. `Eight trolls, thirty-two dwarfs. Dwarfs always start. A dwarf is small and fast and can run as many squares as possible in any direction. A troll - because we're stupid and drag our clubs, as everyone knows - can move only one square in any direction. There are other types of moving, but what do you see so far?'

Vimes tried to concentrate. It was hard. This was a game, it wasn't real. Besides, the answer was so obvious that it couldn't be the right one.

`It looks like the dwarfs must win every time,' he ventured.

`Ah, natural suspicion, I like that. In fact, among the best players the bias is slightly in favour of the trolls,' said Mr Shine. `This is largely because a troll can, in the right circumstances, do a lot of damage. How are your ribs, by the way?'

`All the better for you asking,' said Vimes sourly. He'd forgotten them for twenty blessed minutes; now they ached again.

`Good. I'm glad Brick has found Detritus. He has a good brain if he can be persuaded to stop frying it every half an hour. Back to our game... advantages to either side do not matter, in fact, because a complete game consists of two battles. In one, you must play the dwarfs. In the other, you must play the trolls. As you may expect, dwarfs find it easy to play the dwarf side, which needs a strategy and mode of attack that comes easily to a dwarf. Something similar applies to the trolls. But to win you must play both sides. You must, in fact, be able to think like your ancient enemy. A really skilled player- Well, take a look, commander. Look towards the back of the room where my friend Phyllite is playing against Nils Mousehammer.'

Vimes turned. `What am I looking for?' he said.

`Whatever you see.'

`Well, that troll over there is wearing what looks like a large dwarf helmet. .

`Yes, one of the dwarf players made it for him. And he speaks quite passable dwarfish.'

`He's drinking out of a horn, like the dwarfs do. ..'

`He had to have one made in metal! Troll beer would melt through ordinary horn. Nils there can sing quite a lot of the troll history chant. Look at Gabbro, over there. Good troll boy, but he knows all there is to know about dwarf battle bread. In fact, I believe that's a boomerang croissant on the table next to him. Purely for ceremonial purposes, of course. Commander?'

`Hmm?' said Vimes. `What?' A slightly built dwarf at one of the tables was watching him with interest, as though he was some kind of fascinating monster.

Mr Shine chuckled. `To study the enemy you have to get under his skin. When you're under his skin you start to see the world through his eyes. Gabbro is so good at playing from the dwarf viewpoint that his troll game is suffering, and he wants to go to Copperhead to learn from some of the dwarf thudmeisters there. I hope he does; they'll teach him how to play like a troll. None of these lads here were out getting fighting drunk last night. And thus we wear down mountains. Water dripping on a stone, dissolving and removing. Changing the shape of the world, one drop at a time. Water dripping on a stone, commander. Water

flowing underground, bubbling up in unexpected places.'

`I think you're going to need a bit more of a gush,' said Vimes. `I don't think a bunch of people playing games is going to break down a mountain any time soon.'

`It depends on where the drops fall,' said Mr Shine. `In time they may wash away a valley, at least. You should ask yourself why you were so keen to get into that mine.'

`Because there had been a murder!'

`And that was the only reason?' said the shrouded Mr Shine. `Of course!'

`And everyone knows what gossips dwarfs are,' said Mr Shine. `Well, I am sure you will do your best, commander. I hope you find the murderer before the Dark catches up with them.'

`Mr Shine, some of my officers have lit candles around that damn symbol!

'Good thinking, I'd say.'

`So you really believe that it's some kind of a threat? How come you know so much about dwarf signs, anyway?'

`I have studied them. I accept the fact of their existence. Some of your officers believe. Most dwarfs do, somewhere in their gnarly little souls. I respect that. You can take a dwarf out of the dark, but you can't take the dark out of a dwarf. Those symbols are very old. They have real power. Who knows what old evil exists in the deep darkness under the mountains? There's no darkness like it.'

`You can take the mickey out of a copper, too,' said Vimes.

`Ah, Mister Vimes, you have had a busy day. So much happening, so little time to think. Take time to reflect on all you know, sir. I am a reflecting kind of person.'

`Commander Vimes?' The voice came from Miss Pickles/ Pointer, halfway up the stairs. `There is a big troll asking after you.

`What a shame,' said Mr Shine. `That will be Sergeant Detritus. Not good news, I suspect. If I had to guess, I'd say that the trolls

have sent around the taka-taka. You must go, Mister Vimes. I'll be seeing you again.'

`I don't think I'll see you,' said Vimes. He stood up, and then hesitated.

`One question, right? And no funny answers, if you don't mind,' he said. `Tell me why you helped Brick. Why should you care about a slushed-out gutter troll?'

`Why should you care about some dead dwarfs?' said Mr Shine.

`Because someone has to!'

`Exactly! Goodbye, Mister Vimes.'

Vimes hurried up the stairs and followed Miss Pickles/Pointer out into the shop. Detritus was standing among the mineral specimens, looking uncomfortable, like a man in a morgue.

`What's happening?' said Vimes.

Detritus shifted uneasily. `Sorry, Mister Vimes, but I was the only one dat knew where-' he began.

`Yes, okay. Is this about the taka-taka?'

`How did you know about that, sir?'

`I don't. What is the taka-taka?'

`It der famous war club of der trolls,' said Detritus. Vimes, with the image of the peace club of the trolls downstairs still in his mind, couldn't stop himself.