'Not in four dimensions,' said Unity. 'In eighteen, it's all perfectly clear.'

'And now, may I suggest you ladies leave by the back way?' said Lu-Tze. 'People are going to come running down here in a minute and it's all going to get very excitable. Probably best if you aren't around.'

'What will you do?' said Susan. 'Lie,' said Lu-Tze happily. 'It's amazing how often that works.' -ick Susan and Unity stepped out of a door in the rock. A path led through rhododendron groves out of the valley. The sun was touching the horizon and the air was warm, although there were snowfields quite close by. At the lip of the valley the water from the stream plunged over a cliff in a fall so long that it landed as a sort of rain. Susan pulled herself onto a rock, and settled down to wait. 'It is a long way to Ankh-Morpork,' said Unity. 'We'll have a lift,' said Susan. The first stars were already coming out. 'The stars are very pretty,' said Unity. 'Do you really think so?'

'I am learning to. Humans believe they are.'

'The thing is, I mean, there's times when you look at the universe and you think, “What about me?” and you can just hear the universe replying, “Well, what about you?”' Unity appeared to consider this. 'Well, what about you?' she said. Susan sighed. 'Exactly.' She sighed again. 'You can't think about just one person while you're saving the world. You have to be a cold, calculating bastard.'

'That sounded as if you were quoting somebody,' said Unity. 'Who said that?'

'Some total idiot,' said Susan. She tried to think of other things, and added, 'We didn't get all of them. There's still Auditors down there somewhere.'

'That will not matter,' said Unity calmly. 'Look at the sun.'

'Well?'

'It is setting.'

'And...?'

'That means time is flowing through the world. The body exacts its toll Susan. Soon my- my former colleagues, bewildered and fleeing, will become tired. They will have to sleep.'

'I follow you, but-'

'I am insane. I know this. But the first time it happened to me I found such horror that I cannot express it. Can you imagine what it is like? For an intellect a billion years old, in a body which is an ape on the back of a rat that grew out of a lizard? Can you imagine what comes out of the dark places, uncontrolled?'

'What are you telling me?'

'They will die in their dreams.' Susan thought about this. Millions and millions of years of thinking precise, logical thoughts - and then humanity's murky past drops all its terrors on you in one go. She could almost feel sorry for them. Almost. 'But you didn't,' she said. 'No. I think I must be... different. It is a terrible thing to be different, Susan. Did you have romantic hopes in connection with the boy?' The question came out of nowhere and there was no defence. Unity's face showed nothing but a kind of nervous concern. 'No,' said Susan. Unfortunately, Unity did not seem to have mastered some of the subtleties of human conversation, such as when a tone of voice means 'Stop this line of inquiry right now or may huge rats eat you by day and by night.'

'I confess to strange feelings regarding his... self that was the clockmaker. Sometimes, when he smiled, he was normal. I wanted to help him, because he seemed so closed in and sad.'

'You don't have to confess to things like that,' Susan snapped. 'How do you even know the word romantic, anyway?' she added. 'I found some books of poetry.' Unity actually looked embarrassed. 'Really? I've never trusted it,' said Susan. Huge, giant, hungry rats. 'I found it most curious. How can words on a page have a power like that? There is no doubt that being human is incredibly difficult and cannot be mastered in one lifetime,' said Unity sadly.

Susan felt a stab of guilt. It wasn't Unity's fault, after all. People learn things as they grow up, things that never get written down. And Unity had never grown up. 'What are you going to do now?' she said. 'I do have a rather human ambition,' said Unity. 'Well, if I can help in any way...' It was, she realized later, one of those phrases like 'How are you?' People were supposed to understand that it wasn't a real question. But Unity hadn't learned that, either. 'Thank you. You can indeed help.'

'Uh, fine, if-'

'I wish to die.' And, galloping out of the sunset, some riders were approaching. Tick Small fires burned in the rubble, brightening the night. Most of the houses had been completely destroyed, although, Soto considered, the word 'shredded' was much more accurate. He was sitting by the side of the street, watching carefully, with his begging bowl in front of him. There were of course far more interesting and complex ways for a History Monk to avoid being noticed, but he'd adopted the begging bowl method ever since Lu-Tze had shown him that people never see anyone who wants them to give him money. He'd watched the rescuers drag the bodies out of the house. Initially they'd thought that one of them had been hideously mutilated in the explosion, until it had sat up and explained that it was an Igor and in very good shape for an Igor, at that. The other he'd recognized as Dr Hopkins of the Guild of Clockmakers, who was miraculously unharmed. Soto did not believe in miracles, however. He was also suspicious about the fact that the ruined house was full of oranges, that Dr Hopkins was babbling about getting sunlight out of them, and that his sparkling little abacus was telling him that something enormous had happened. He decided to make a report and see what the boys at Oi Dong said. Soto picked up the bowl and set off through the network of alleys back to his base. He didn't bother much about concealment now; Lu-Tze's time in the city had been a process of accelerated education for many citizens of the lurking variety. The people of Ankh-Morpork knew all about Rule One. At least, they had known until now. Three figures lurched out of the dark, and one of them swung a heavy cleaver which would have connected with Soto's head if he hadn't ducked.

He was used to this sort of thing, of course. There was always the occasional slow learner, but they presented no peril that a neat slice couldn't handle. He straightened up, ready to ease his way out of there, and a thick lock of black hair fell onto his shoulder, slithered down his robe and flopped onto the ground. It made barely a sound, but the expression on his face as Soto looked down and then up at his attackers made them draw back. He could see, through the blood-red rage, that they all wore stained grey clothes and looked even crazier than the usual alley people; they looked like accountants gone mad. One of them reached out towards the begging bowl. Everyone has a conditional clause in their life, some little unspoken addition to the rules like 'except when I really need to' or 'unless no one is looking' or, indeed, 'unless the first one was nougat'. Soto had for centuries embraced a belief in the sanctity of all life and the ultimate uselessness of violence, but his personal conditional clause was 'but not the hair. No one touches the hair, okay?' Even so, everyone ought to have a chance. The attackers recoiled as he threw the bowl against the wall, where the hidden blades buried themselves in the woodwork. Then it began to tick. Solo ran back down the alley, skidded round the corner and then shouted, 'Duck!' Unfortunately for the Auditors, alas, he was just a tiny, tiny fraction of a second too late- Tick Lu-Tze was in his Garden of Five Surprises when the air sparkled and fragmented and swirled into a shape in front of him. He looked up from his ministrations to the yodelling stick insect, who'd been off its food. Lobsang stood on the path. The boy was wearing a black robe dotted with stars, which blew and rattled its rags around him on this windless morning as if he was standing in the centre of a gale. Which, Lu-Tze supposed, he more or less was. 'Back again, wonder boy?' said the sweeper. 'In a way, I never leave,' said Lobsang. 'Things have gone well with you?'

'Don't you know?'

'I could. But part of me has to do this the traditional way.'

'Well, the abbot is mighty suspicious and there's some amazing rumours flying around the place. I didn't say much. What do I know about anything? I'm just a sweeper.' With that, Lu-Tze turned his attention to the sick insect. He'd counted to four under his breath before Lobsang said: 'Please? I have to know. I believe that the fifth surprise is you. Am I right?' Lu-Tze cocked his head. A low noise, which he'd heard for so long he no longer consciously heard it, had changed its tone. 'The spinners are all winding out,' he said. 'They know you're here, lad.'

'I shall not be here long, Sweeper. Please?'

'You just want to know my little surprise?'

'Yes. I know nearly everything else,' said Lobsang. 'But you are Time. What I tell you in the future you'll know now, right?'

'But I'm partly human. I want to stay partly human. That means doings things the right way round. Please?' Lu-Tze sighed and looked for a while down the avenue of cherry blossom. 'When the pupil can beat the master, there is nothing the master cannot tell him,' he said. 'Remember?'

'Yes.'

'Very well. The Iron Dojo should be free.' Lobsang looked surprised. 'Uh, the Iron Dojo ... Isn't that the one with all the sharp spikes in the walls?'

'And the ceiling, yes. The one that's like being inside a giant porcupine turned inside out.' Lobsang looked horrified. 'But that's not for practice! The rules say-'

'That's the one,' said Lu-Tze. 'And I say we use it.'

'Oh.'

'Good. No argument,' said Lu-Tze. 'This way, lad.' Blossom cascaded from the trees as they passed. They entered the monastery, and took the same route they'd taken once before. This brought them into the Hall of the Mandala, and the sand rose like a dog welcoming its master and spiralled in the air far below Lobsang's sandals. Lu-Tze heard the shouts of the attendants behind him.

News like this spread throughout the valley like ink in water. Hundreds of monks, apprentices and sweepers were trailing the pair as they crossed the inner courtyards, like the tail of a comet. Above them, all the time, petals of cherry blossom fell like snow. At last Lu-Tze reached the high, round metal door of the Iron Dojo. The clasp of the door was fifteen feet up. No one who did not belong there was supposed to open the door of the dojo. The sweeper nodded at his former apprentice. 'You do it,' he said. I can't.' Lobsang glanced at him, and then looked up at the high clasp. Then he pressed a hand against the iron. Rust spread under his fingers. Red stains spread out across the ancient metal. The door began to creak, and then to crumble. Lu-Tze prodded it with an experimental finger, and a slab of biscuit-strong metal fell out and collapsed on the flagstones. 'Very impress-' he began. A squeaky rubber elephant bounced off his head. 'Bikkit!' The crowd parted. The chief acolyte ran forward, carrying the abbot. 'What is the wanna bikkit BIKKIT meaning of this? Who is wozza funny man this person, Sweeper? The spinners are dancing in their hall!' Lu-Tze bowed. 'He is Time, reverend one, as you have suspected,' he said. Still bent in the bow, he looked up and sideways at Lobsang. 'Bow!' he hissed. Lobsang looked puzzled. 'I should bow even now?' he said. 'Bow, you little stonga, or I shall teach you such discipline! Show deserved respect! You are still my apprentice until I give you leave!' Shocked, Lobsang bowed. 'And why do you visit us in our timeless valley?' said the abbot. Tell the abbot!' Lu-Tze snapped. 'I... I wish to learn the Fifth Surprise,' said Lobsang. '-reverend one-' said Lu-Tze.

'-reverend one,' Lobsang finished. 'You visit us just to learn of our clever sweeper's fancies?' said the abbot. 'Yes, er, reverend one.'

'Of all the things Time could be doing, you wish to see an old man's trick? Bikkit!'

'Yes, reverend one.' The monks stared at Lobsang. His robe still fluttered this way and that in the teeth of the intangible gale, the stars glinting when they caught the light. The abbot smiled a cherubic smile. 'So should we all,' he said. 'None of us has ever seen it, I believe. None of us has ever been able to wheedle it out of him. But... this is the Iron Dojo. It has rules! Two may walk in, but only one can walk out! This is no practice dojo! Wanna 'lephant! Do you understand?'