Mort hurried out after him. The ancient ancestor watched them go with a critical expression, its jowls rhythmically chewing.

'That was what they call a demon around here?' it said. 'Offler rot this country of dampness, even their demons are third-rate, not a patch on the demons we had in the Old Country.'

The wife placed a small bowl of rice in the folded middle pair of hands of the Offler statue (it would be gone in the morning) and stood back.

'Husband did say that last month at the Curry Gardens he served a creature who was not there,' she said. 'He was impressed.'

Ten minutes later the man returned and, in solemn silence, placed a small heap of gold coins on the table. They represented enough wealth to purchase quite a large part of the city.

'He had a bag of them,' he said.

The family stared at the money for some time. The wife sighed.

'Riches bring many problems,' she said. 'What are we to do?'

'We return to Klatch,' said the husband firmly, 'where our children can grow up in a proper country, true to the glorious traditions of our ancient race and men do not need to work as waiters for wicked masters but can stand tall and proud. And we must leave right now, fragrant blossom of the date palm.'

'Why so soon, O hard-working son of the desert?'

'Because,' said the man, 'I have just sold the Patrician's champion racehorse.'

The horse wasn't as fine or as fast as Binky, but it swept the miles away under its hooves and easily outdistanced a few mounted guards who, for some reason, appeared anxious to talk to Mort. Soon the shanty suburbs of Morpork were left behind and the road ran out into rich black earth country of the Sto plain, constructed over eons by the periodic flooding of the great slow Ankh that brought to the region prosperity, security and chronic arthritis.

It was also extremely boring. As the light distilled from silver to gold Mort galloped across a flat, chilly landscape, chequered with cabbage fields from edge to edge. There are many things to be said about cabbages. One may talk at length about their high vitamin content, their vital iron contribution, the valuable roughage and commendable food value. In the mass, however, they lack a certain something; despite their claim to immense nutritional and moral superiority over, say, daffodils, they have never been a sight to inspire the poet's muse. Unless he was hungry, of course. It was only twenty miles to Sto Lat, but in terms of meaningless human experience it seemed like two thousand.

There were guards on the gates of Sto Lat, although compared to the ones that patrolled Ankh they had a sheepish, amateurish look. Mort trotted past and one of them, feeling a bit of a fool, asked him who went there.

'I'm afraid I can't stop,' said Mort.

The guard was new to the job, and quite keen. Guarding wasn't what he'd been led to expect. Standing around all day in chain mail with an axe on a long pole wasn't what he'd volunteered for; he'd expected excitement and challenge and a crossbow and a uniform that didn't go rusty in the rain.

He stepped forward, ready to defend the city against people who didn't respect commands given by duly authorised civic employees. Mort considered the pike blade hovering a few inches from his face. There was getting to be too much of this.

'On the other hand,' he said calmly, 'how would you like it if I made yon a present of this rather fine horse?'

It wasn't hard to find the entrance to the castle. There were guards there, too, and they had crossbows and a considerably more unsympathetic outlook on life and, in any case, Mort had run out of horses. He loitered a bit until they started paying him a generous amount of attention, and then wandered disconsolately away into the streets of the little city, feeling stupid.

After all this, after miles of brassicas and a backside that now felt like a block of wood, he didn't even know why he was there. So she'd seen him even when he was invisible? Did it mean anything? Of course it didn't. Only he kept seeing her face, and the flicker of hope in her eyes. He wanted to tell her that everything was going to be all right. He wanted to tell her about himself and everything he wanted to be. He wanted to find out which was her room in the castle and watch it all night until the light went out. And so on.

A little later a blacksmith, whose business was in one of the narrow streets that looked out on to the castle walls, glanced up from his work to see a tall, gangling young man, rather red in the face, who kept trying to walk through the walls.

Rather later than that a young man with a few superficial bruises on his head called in at one of the city's taverns and asked for directions to the nearest wizard.

And it was later still that Mort turned up outside a peeling plaster house which announced itself on a blackened brass plaque to be the abode of Igneous Cutwell, DM (Unseen), Marster of the Infinit, Illuminartus, Wyzard to Princes, Gardian of the Sacred Portalls, If Out leave Maile with Mrs Nugent Next Door.

Suitably impressed despite his pounding heart, Mort lifted the heavy knocker, which was in the shape of a repulsive gargoyle with a heavy iron ring in its mouth, and knocked twice.

There was a brief commotion from within, the series of hasty domestic sounds that might, in a less exalted house, have been made by, say, someone shovelling the lunch plates into the sink and tidying the laundry out of sight.

Eventually the door swung open, slowly and mysteriously.

'You'd fbetter pretend to be impreffed,' said the doorknocker conversationally, but hampered somewhat by the ring. 'He does it with pulleys and a bit of ftring. No good at opening-fpells, fee?'

Mort looked at the grinning metal face. I work for a skeleton who can walk through walls, he told himself. Who am I to be surprised at anything?

'Thank you,' he said.

'You're welcome. Wipe your feet on the doormat, it's the bootfcraper's day off.'

The big low room inside was dark and shadowy and smelled mainly of incense but slightly of boiled cabbage arid elderly laundry and the kind of person who throws all his socks at the wall and wears the ones that don't stick. There was a large crystal ball with a crack in it, an astrolabe with several bits missing, a rather scuffed octogram on the floor, and a stuffed alligator hanging from the ceiling. A stuffed alligator is absolutely standard equipment in any properly-run magical establishment. This one looked as though it hadn't enjoyed it much.

A bead curtain on the far wall was flung aside with a dramatic gesture and a hooded figure stood revealed.

'Beneficent constellations shine on the hour of our meeting!' it boomed.

'Which ones?' said Mort.

There was a sudden worried silence.

'Pardon?'

'Which constellations would these be?' said Mort.

'Beneficent ones,' said the figure, uncertainly. It rallied. 'Why do you trouble Igneous Cutwell, Holder of the Eight Keys, Traveller in the Dungeon Dimensions, Supreme Mage of —'

'Excuse me,' said Mort, 'are you really?'

'Really what?'

'Master of the thingy, Lord High Wossname of the Sacred Dungeons?'

Cutwell pushed back his hood with an annoyed flourish. Instead of the grey-bearded mystic Mort had expected he saw a round, rather plump face, pink and white like a pork pie, which it somewhat resembled in other respects. For example, like most pork pies, it didn't have a beard and, like most pork pies, it looked basically good-humoured.

'In a figurative sense,' he said.

'What does that mean?'

'Well, it means no,' said Cutwell.

'But you said —'

'That was advertising,' said the wizard. 'It's a kind of magic I've been working on. What was it you were wanting, anyway?' He leered suggestively. 'A love philtre, yes? Something to encourage the young ladies?'

'Is it possible to walk through walls?' said Mort desperately. Cutwell paused with his hand already halfway to a large bottle full of sticky liquid.

'Using magic?'

'Um,' said Mort, 'I don't think so.'

Then pick very thin walls,' said Cutwell. 'Better still, use the door. The one over there would be favourite, if you've just come here to waste my time.'

Mort hesitated, and then put the bag of gold coins on the table. The wizard glanced at them, made a little whinnying noise in the back of his throat, and reached out, Mort's hand shot across and grabbed his wrist.

'I've walked through walls,' he said, slowly and deliberately.

'Of course you have, of course you have,' mumbled Cutwell, not taking his eyes off the bag. He flicked the cork out of the bottle of blue liquid and took an absent-minded swig.

'Only before I did it I didn't know that I could, and when I was doing it I didn't know I was, and now I've done it I can't remember how it was done. And I want to do it again.'

'Why?'

'Because,' said Mort, 'if I could walk through walls I could do anything.'

'Very deep,' agreed Cutwell. 'Philosophical. And the name of the young lady on the other side of this wall?'

'She's —' Mort swallowed. 'I don't know her name. Even if there is a girl,' he added haughtily, 'and I'm not saying there is.'

'Right,' said Cutwell. He took another swig, and shuddered. 'Fine. How to walk through walls. I'll do some research. It might be expensive, though.'

Mort carefully picked up the bag and pulled out one small gold coin.

'A down payment,' he said, putting it on the table.

Cutwell picked up the coin as if he expected it to go bang or evaporate, and examined it carefully.

'I've never seen this sort of coin before,' he said accusingly. 'What's all this curly writing?'

'It's gold, though, isn't it?' said Mort. 'I mean, you don't have to accept it —'

'Sure, sure, it's gold,' said Cutwell hurriedly. 'It's gold all right. I just wondered where it had come from, that's all.'

'You wouldn't believe me,' said Mort. 'What time's sunset around here?'

'We normally manage to fit it in between night and day,' said Cutwell, still staring at the coin and taking little sips from the blue bottle. 'About now.'

Mort glanced out of the window. The street outside already had a twilight look to it.

'I'll be back,' he muttered, and made for the door. He heard the wizard call out something, but Mort was heading down the street at a dead run.

He started to panic. Death would be waiting for him forty miles away. There would be a row. There would be a terrible —

AH, BOY.

A familiar figure stepped out from the flare around a jellied eel stall, holding a plate of winkles.

THE VINEGAR IS PARTICULARLY PIQUANT. HELP YOURSELF, I HAVE AN EXTRA PIN.

But, of course, just because he was forty miles away didn't mean he wasn't here as well. . . .

And in his untidy room Cutwell turned the gold coin over and over in his fingers, muttering 'walls' to himself, and draining the bottle.

He appeared to notice what he was doing only when there was no more to drink, at which point his eyes focused on the bottle and, through a rising pink mist, read the label which said 'Granny Weatherwax's Ramrub Invigoratore and Passion's Philtre, Onne Spoonful Onlie before bed and that Smalle'.

'By myself?' said Mort.

CERTAINLY. I HAVE EVERY FAITH IN YOU.

'Gosh!'

The suggestion put everything else out of Mort's mind, and he was rather surprised to find that he didn't feel particularly squeamish. He'd seen quite a few deaths in the last week or so, and all the horror went out of it when you knew you'd be speaking to the victim afterwards. Most of them were relieved, one or two of them were angry, but they were all glad of a few helpful words.

THINK YOU CAN DO IT?

'Well, sir. Yes. I think.'

THAT'S THE SPIRIT. I'VE LEFT BlNKY BY THE HORSETROUGH ROUND THE CORNER. TAKE HIM STRAIGHT HOME WHEN YOU'VE FINISHED.