'Will you stop talking about jam and be sensible for a moment!'

Rincewind lowered the sandwich. 'Good grief, I hope not,' he said. 'I'm sitting in a cave in a country where everything bites you and it never rains and I'm talking, no offence, to a herbivore that smells of a carpet in a house where there are a lot of excitable puppies, and I've suddenly got this talent for finding jam sandwiches and inexplicable fairy cakes in unexpected places, and I've been shown something very odd in a picture on some old cave wall, and suddenly said kangaroo tells me time and space are all wrong and wants me to be sensible? What, when you get right down to it, is in it for me?'

'Look, this place wasn't finished, right? It wasn't fitted in... turned around...' The kangaroo looked at Rincewind as if reading his mind, which was the case. 'You know like with a jigsaw puzzle? The last piece is the right shape but you have to turn it round to fit? Right? Now think of the piece as a bloody big continent that's got to be turned around through about nine dimensions and you're home and...'

'Dry?' said Rincewind.

'Bloody right!'

'Er... I know this may seem like a foolish question,' said Rincewind, trying to dislodge a gooseberry pip from a tooth cavity, 'but why me?'

'It's your fault. You arrived here and suddenly things had always been wrong.'

Rincewind looked back towards the wall. The earth trembled again.

'Can you hop that past me again?' he said.

'Something went wrong in the past.'

The kangaroo looked at Rincewind's blank, jam-smeared expression, and tried again.

'Your arrival caused a wrong note,' it ventured.

'What in?'

The creature waved a paw vaguely.

'All this,' it said. 'You could call it a bloody multi-dimensional knuckle of localized phase space, or maybe you could just call it the song.'

Rincewind shrugged. 'I don't mind putting my hand up to killing a few spiders,' he said. 'But it was me or them. I mean some of those come at you at head height—'

'You changed history.'

'Oh, come on, a few spiders don't make that much difference, some of them were using their webs as trampolines, it was a case of "boing" and next moment—'

'No, not history from now on, history that's already happened,' said the kangaroo.

'I've changed things that already happened long ago?'

'Right.'

'By arriving here I changed what's already happened!'

'Yep. Look, time isn't as straightforward as you think—'

'I never thought it was,' said Rincewind. 'And I've been round it a few times...'

The kangaroo waved a paw expansively. 'It's not just that things in the future can affect things in the past,' he said. 'Things that didn't happen but might have happened can... affect things that really happened. Even things that happened and shouldn't have happened and were removed still have, oh, call 'em shadows in time, things left over which interfere with what's going on. Between you and me,' it went on, waggling its ears, 'it's all just held together by spit now. No one's ever got round to tidying it up. I'm always amazed when tomorrow follows today, and that's the truth.'

'Me too,' said Rincewind. 'Oh, me too.'

'Still, no worries, eh?'

'I think I'll lay off the jam,' said Rincewind. He put the sandwich down. 'Why me?'

The kangaroo scratched its nose, ' 's got to be someone,' it said.

'And what'm I supposed to do?' said Rincewind.

'Wind it into the world.'

'There's a key?'

'Might be. Depends.'

Rincewind turned and looked at the rock pictures again, the pictures that hadn't been there a few weeks ago and then suddenly had always been there.

Figures holding long sticks. Figures in long robes. The artist had done a pretty good job of drawing something quite unfamiliar. And in case there was any doubt, you only had to look at what was on their heads.

'Yeah. We call them The Pointy-Heads,' said the kangaroo.

'He's started catching fish,' said the Senior Wrangler. 'That means he'll come over all smug and start asking what plans we've got for making a boat at any minute, you know what he's like.'

The Dean looked at some sketches he'd made on a rock.

'How hard can it be to build a boat?' he said.

'People with bones in their noses build boats. And we are the end product of thousands of years of enlightenment. Building a boat is not beyond men like us, Senior Wrangler.'

'Quite, Dean.'

'All we have to do is search this island until we find a book with a title like Practical Boat-building for Beginners.'

'Exactly. It'll be plain sailing after that, Dean. Ahaha.'

He glanced up, and swallowed hard. Mrs Whitlow was sitting on a log in the shade, fanning herself with a large leaf.

The sight stirred things in the Senior Wrangler. He was not at all sure what they were, but little details like the way something creaked when she moved twanged bits of the Senior Wrangler as well.

'You all right, Senior Wrangler? You look as if the heat is getting to you.'

'Just a little... warm, Dean.'

The Dean looked past him as he loosened his collar. 'Well, they haven't been long,' he said.

The other wizards were walking down the beach. One advantage of a long wizarding robe is that it can be held like an apron, and the Chair of Indefinite Studies was bulging at the front even more than usual.

'Found anything to eat?' said the Senior Wrangler.

'Er... yes.'

'Fruit and nuts, I suppose,' grumbled the Dean.

'Er... yes, and then again, no,' said the Lecturer in Recent Runes. 'Um... it's rather odd...'

The Chair of Indefinite Studies let his burden spill out on to the sand. There were coconuts, other nuts of various sizes, and assorted hairy or knobbly vegetable things.

'All rather primitive,' said the Dean. 'And probably poisonous.'

'Well, the Bursar's been eating things like there's no tomorrow,' said the Lecturer in Recent Runes. The Bursar burped happily.

'That doesn't mean there will be,' said the Dean. 'What's up with you fellows? You keep looking at one another.'

'Er... we've tasted a few things too, Dean,' said the Lecturer in Recent Runes.

'Ah, I see the gatherers have returned!' roared Ridcully happily, walking towards them. He waved three fish on a string. 'Anything resembling potatoes in there, chaps?'

'You're not going to believe any of this,' mumbled the Lecturer in Recent Runes. 'You're going to accuse us of trickery.'

'What are you talking about?' said the Dean. 'They don't look very tricky to me.'

The Chair of Indefinite Studies gave a sigh. 'Have a coconut,' he said.

'Do they go off bang or something?'

'No, nothing like that at all.'

The Dean picked up a nut, gave it a suspicious look, and banged it on a stone. It fell into two exact halves.

There was no milk to spill out. Inside the husk was a brown inner shell, full of soft white fibres.

Ridcully picked up a bit of it and sniffed. 'I don't believe this,' he said. 'That's not natural.'

'So?' said the Dean. 'It's a coconut full of coconut. What's odd about that?'

The Archchancellor broke off a piece of the shell and handed it over. It was soft and slightly crumbly.

The Dean tasted it. 'Chocolate?' he said.

Ridcully nodded. 'Dairy milk, by the taste of it. With a creamy coconut filling.'

That's nod poffible,' said the Dean, his cheeks bulging.

'Spit it out, then.'

'I think I might perhaps try a little more,' said the Dean, swallowing. 'In a spirit of enquiry, you understand.'

The Senior Wrangler picked up a knobbly bluish nut about the size of a fist and tapped it experimentally. It shattered but was held together because of the gooey contents.