‘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.