`I've got an idea,' said Rincewind. The other wizards turned, amazed at this revelation.

`Yes?' said Ponder.

`Why not just take it for granted that someone is out to get you?' said Rincewind. `That's what I do. Don't bother to work out the fine detail. Look, when you first started to tinker, it was all going to be plain sailing, right? Make a few little adjustments, pinch a fish, and it'd all be OK? But now there are nearly fifteen hundred new reasons-'

With a rattle, Hex's writing desk started up. The pens wrote: +++ 3563 reasons now +++

`They're breeding!' said Ridcully.

`There you are, then,' said Rincewind, almost cheerfully. `Something down there is frightened. It's so frightened that it's not even going to let him get on the boat. I mean, he has to take the voyage whatever book he writes, isn't that right!'

`Yes, of course,' said Ponder. Theology of Species gets taken seriously because it's written by a renowned and respected scientist whose research was meticulous. So was The Origin. Either way, he needs to be on that boat. But the moment we take an interest, the voyage doesn't happen!'

`Then if it was me, I'd say that something's got really worried,' said Rincewind. `They don't mind if The Ology doesn't get written in just one universe, but they hate the idea of The Origin being written at all.

`Oh, really?' said Ridcully. `The nerve! I am the master of this college, and that - ' he pointed to the little globe ' - is university property! Now I'm getting angry. We're going to fight back, Mr Stibbons!'

`I don't think you can fight a whole universe, sir! 'It's the prerogative of every life form, Mr Stibbons!'

Gales roared for three weeks. Roundworld time was mutable for the wizards; it only affected them if they wanted it to.

Something or someone didn't want the Beagle to sail, and they could influence the weather. They could influence anything. But of them, there was still no sign.

The Dean watched the storm in the big omniscope in the HEM.

`That's what happened when Darwin gets on board in this universe,' said Ponder, adjusting the omniscope. `If he hadn't gone, his place is taken by an artist, who produced a famous portfolio as a result. His name was Preserved J. Nightingale. You met his wife.'

`Preserved?' said the Dean, watching the dismal gale.

`Short for Preserved-by-God,' said Ponder. `He was found as a child in the wreckage of a ship. His adopted parents were very religious. And ... ah yes ... this is the weather they get when he is on board.'

The omniscope flickered.

`No gale?' said the Dean, looking at the blue sky.

`Brisk winds from the north-east. They're ball-world directions, sir. For the purposes of the voyage, they are ideal. I see you have your "Born to Rune" jacket on, sir.'

`We've got a fight on our hands, Stibbons,' said the Dean, severely. `It's a long time since I've seen the Archchancellor so angry at anyone but me! Have you finished?'

'Just finishing, sir,' said Ponder.

The HEM had a deserted look. That was because it had been, by and large, deserted. Thick tubes led out from Hex, across the floor and out over the lawn towards UU's Great Hall.

The wizards were going to war. It took a lot to make that happen, but you couldn't let any old universe push you around. Gods, demons and Death were one thing, but mindless matter shouldn't be allowed to get ideas.

`Couldn't we just find a way to bring Darwin back here?' said the Dean, watching Ponder prod buttons on Hex's keyboard.

`Quite probably, sir,' said Ponder.

`Well, then, why don't we just bring him here, explain the situation, and drop him off on his island? We could even give him a copy of his book.'

Ponder shuddered.

`There are quite a lot of reasons why that course of action might not, with ease, be rescued in any coherent way from the category of the insanely unwise, Dean,' he said, having worked out that the senior wizards lost interest in any sentence that went on past twenty words. `For one thing, he'd know.'

`We could bop him on the head,' said the Dean. `Or put a 'fluence on him. Yes, that'd be a good idea,' he said, because it was his. `We could sit him in a comfy chair and read out the right book to him. He'd wake up back home and think he's made it all up.'

`But he wouldn't have been there,' said Ponder. He waved a hand. In the air overhead, a little ball of multicoloured light appeared. It looked like a tangle of glowing strings, or the mating of rainbows.

`Oh, we could sort that out,' said the Dean airily. `Stick some sand in his boots, a few finch feathers in his pocket ... we are wizards, after all.'

`That would be unethical, Dean,' said Ridcully. `Why? We're the Good Guys, aren't we?'

`Yes, but that rather hinges on doing certain things and not doing others, sir,' said Ponder. `Playing around with people's heads against their will is almost certainly one of the nots. You should get ready to move quickly, sir.'

`What are you doing, Stibbons?'

`I've got Hex to cast a thaumatic glyph in conditional Darwin space,' said Ponder. `But to resolve it properly Hex will have to run the thaumic reactor a little higher than usual.'

`How much higher?' said the Dean suspiciously. `About 200 per cent, sir.'

`Is that safe?'

`Absolutely not, sir. Hex, glyphic resolution in twenty seconds. Dean, run! Run, sir!'

From the direction of the Old Squash Court came a sound that had been there all the time, unheeded, and was now growing louder. It was the whum whum of dying thaums, each one yielding up its intrinsic magic ...

Wizards have a wonderful turn of speed.

Ponder and the Dean reached the Great Hall in twelve seconds, the Dean slightly in the lead. The ball of rainbows had got there before them, though, and hung high over the black and white flagstones of the floor.

The hall was packed with wizards. Teams had been sent out to the furthest corners of the university, which were pretty far. Space and time had long ago been warped by the ancient magical stones, and there were wizards at UU who had happily occupied nooks and corners for decades or longer, regarding the Great Hall and surrounding buildings as the colonists on some faraway continent might regard the ancient mother country. Distant studies had been broken into and their occupants dragged out or, in some unfortunate cases, swept up. Wizards that Ponder had never seen before were in the throng, blinking in the light of common day.

Panting slightly, Ponder hurried over to Ridcully.

`You said you wanted a map, sir,' he said.

`Yes, Stibbons. Can't plan a campaign without a map!'

`Then look up now, sir! Here it comes!'

The air wavered for a moment, and then the mated rainbows gave birth. Frozen streamers of light looped through the hazy air of the hall. They twisted and tangled and curved in ways that suggested more than the everyday four dimensions were involved.

`Looks very pretty,' said the Archchancellor, blinking. 'Er ...'

`I thought it would help us sort out further nodalities,' said Ponder.

`Ah yes, good idea,' said Ridcully. `No one wants unsorted nodalities.' The other senior wizards nodded sagely.

`By which I mean,' Ponder added, `it will show us those points where our intervention will have been going to be was essential, if I can put it that way.'

`Oh,' said the Archchancellor. `Er ... what does the coloured line mean, exactly?'

`Which one, sir?'

`All of them, man!'

`Well, the points of intervention that require a human show up as red circles. Those that can be left to Hex are white. The blue lines represent the author of, ahem, The Ology, the yellow lines is the optimum path for the author of The Origin, and the green line represent slippage between futures. Known thaumic occlusions are purple, but I expect you worked that out already.'