‘What Mr Stibbons means, my lord,’ said the Archchancellor, ‘is that there are billions and billions of futures that, er, sort of exist, d'yer see? They're all… the possible shapes of the future. But apparently the first one you actually look at is the one that becomes the future. It might not be one you'd like. Apparently it's all to do with the Uncertainty Principle.’

‘And that is…?’

‘I'm not sure. Mr Stibbons is the one who knows about that sort of thing.’

An orangutan ambled past, carrying an extremely large number of books under each arm. Lord Vetinari looked at the hoses that snaked from the omniscope and out through the open door and across the lawn to… what was it?… the High Energy Magic building?

He remembered the old days, when wizards had been gaunt and edgy and full of guile. They wouldn't have allowed an Uncertainty Principle to exist for any length of time; if you weren't certain, they'd say, what were you doing wrong? What you were uncertain of could kill you.

The omniscope flickered and showed a snowfield, with black mountains in the distance. The wizard called Ponder Stibbons appeared to be very pleased with this.

‘I thought you said you could find him with this thing?’ said Vetinari to the Archchancellor.

Ponder Stibbons looked up. ‘Do we have something that he has owned? Some personal item he has left lying around?’ he said. ‘We could put it in the morphic resonator, connect that up to the omniscope and it'll home in on him like a shot.’

‘Whatever happened to the magic circles and dribbly candles?’ said Lord Vetinari.

‘Oh, they're for when we're not in a hurry, sir,’ said Ponder.

‘Cohen the Barbarian is not known for leaving things lying around, I fear,’ said the Patrician. ‘Bodies, perhaps. All we know is that he is heading for Cori Celesti.’

‘The mountain at the Hub of the world, sir? Why?’

‘I was hoping you would tell me, Mr Stibbons. That's why I'm here.’

The Librarian ambled past again, with another load of books. Another response of the wizards, when faced with a new and unique situation, was to look through their libraries to see if it had ever happened before. This was, Lord Vetinari reflected, a good survival trait. It meant that in times of danger you spent the day sitting very quietly in a building with very thick walls.

He looked again at the piece of paper in his hand. Why were people so stupid? One sentence caught his eye: ‘He says the last hero ought to return what the first hero stole.’

And, of course, everyone knew what the first hero stole.

The gods play games with the fate of men. Not complex ones, obviously, because gods lack patience.

Cheating is part of the rules. And gods play hard. To lose all believers is, for a god, the end. But a believer who survives the game gains honour and extra belief. Who wins with the most believers, lives.

Believers can include other gods, of course. Gods believe in belief.

There were always many games going on in Dunmanifestin, the abode of the gods on Cori Celesti. It looked, from outside, like a crowded city.3 Not all gods lived there, many of them being bound to a particular country or, in the case of the smaller ones, even one tree. But it was a Good Address. It was where you hung your metaphysical equivalent of the shiny brass plate, like those small discreet buildings in the smarter areas of major cities which nevertheless appear to house one hundred and fifty lawyers and accountants, presumably on some sort of shelving.

The city's domestic appearance was because, while people are influenced by gods, so gods are influenced by people.

Most gods were people-shaped; people don't have much imagination, on the whole. Even Offler the Crocodile God was only crocodile-headed. Ask people to imagine an animal god and they will, basically, come up with the idea of someone in a really bad mask. Men have been much better at inventing demons, which is why there are so many.

Above the wheel of the world, the gods played on. They sometimes forgot what happened if you let a pawn get all the way up the board.

It took a little longer for the rumour to spread around the city, but in twos and threes the leaders of the great Guilds hurried into the University.

Then the ambassadors picked up the news. Around the city the big semaphore towers faltered in their endless task of exporting market prices to the world, sent the signal to clear the line for high-priority emergency traffic, and then clack'd the little packets of doom to chancelleries and castles across the continent.

They were in code, of course. If you have news about the end of the world, you don't want everyone to know.

Lord Vetinari stared along the table. A lot had been happening in the past few hours.

‘If I may recap, then, ladies and gentlemen,’ he said, as the hubbub died away, ‘according to the authorities in Hunghung, the capital of the Agatean Empire, the Emperor Ghengiz Cohen, formerly known to the world as Cohen the Barbarian, is well en route to the home of the gods with a device of considerable destructive power and the intention, apparently, of, in his words, “returning what was stolen”. And, in short, they ask us to stop him.’

‘Why us?’ said Mr Boggis, head of the Thieves' Guild. ‘He's not our Emperor!’

‘I understand the Agatean government believes us to be capable of anything,’ said Lord Vetinari. ‘We have zip, zing, vim and a go-getting, can-do attitude.’

‘Can do what?’

Lord Vetinari shrugged. ‘In this case, save the world.’

‘But we'll have to save it for everyone, right?’ said Mr Boggis. ‘Even foreigners?’

‘Well, yes. You cannot just save the bits you like,’ said Lord Vetinari. ‘But the thing about saving the world, gentlemen and ladies, is that it inevitably includes whatever you happen to be standing on. So let us move forward. Can magic help us, Archchancellor?’

‘No. Nothing magical can get within a hundred miles of the mountains,’ said the Archchancellor.

‘Why not?’

‘For the same reason you can't sail a boat into a hurricane. There's just toomuchmagic. It overloads anything magical. A magic carpet would unravel in midair.’

‘Or turn into broccoli,’ said the Dean. ‘Or a small volume of poetry.’

‘Are you saying that we cannot get there in time?’

‘Well… yes. Exactly. Of course. They're already near the base of the mountain.’

‘And they're heroes,’ said Mr Betteridge of the Guild of Historians.

‘And that means, exactly?’ said the Patrician, sighing.

‘They're good at doing what they want to do.’

‘But they are also, as I understand it, very old men.’

‘Very old heroes,’ the historian corrected him. ‘That just means they've had a lot of experience in doing what they want to do.’

Lord Vetinari sighed again. He did not like to live in a world of heroes. You had civilisation, such as it was, and you had heroes.

‘What exactly has Cohen the Barbarian done that is heroic?’ he said. ‘I seek only to understand.’

‘Well… you know… heroic deeds…’

‘And they are…?’

‘Fighting monsters, defeating tyrants, stealing rare treasures, rescuing maidens… that sort of thing,’ said Mr Betteridge vaguely. ‘You know… heroic things.’

‘And who, precisely, defines the monstrousness of the monsters and the tyranny of the tyrants?’ said Lord Vetinari, his voice suddenly like a scalpel – not vicious like a sword, but probing its edge into vulnerable places.

Mr Betteridge shifted uneasily. ‘Well… the hero, I suppose.’

‘Ah. And the theft of these rare items… I think the word that interests me here is the term “theft”, an activity frowned on by most of the world's major religions, is it not? The feeling stealing over me is that all these terms are defined by the hero. You could say: I am a hero, so when I kill you that makes you, defacto, the kind of person suitable to be killed by a hero. You could say that a hero, in short, is someone who indulges every whim that, within the rule of law, would have him behind bars or swiftly dancing what I believe is known as the hemp fandango. The words we might use are: murder, pillage, theft and rape. Have I understood the situation?’