"You want mother," said the tall girl. "Mother! There's a gentleman!"

A distant muttering became a closer muttering, and then Mrs. Cake appeared around the side of her daughter like a small moon emerging from planetary shadow.

"What d'yew want?" said Mrs. Cake.

Windle took a step backwards. Unlike her daughter, Mrs. Cake was quite short, and almost perfectly circular. And still unlike her daughter, whose whole stance was dedicated to making herself look small, she loomed tremendously. This was largely because of her hat, which he later learned she wore at all times with the dedication of a wizard. It was huge and black and had things on it, like bird wings and wax cherries and hatpins; Carmen Miranda could have worn that hat to the funeral of a continent. Mrs. Cake travelled underneath it as the basket travels under a balloon.

People often found themselves talking to her hat.

"Mrs. Cake?" said Windle, fascinated.

"Oim down 'ere," said a reproachful voice.

Windle lowered his gaze.

"That's 'oo I am, " said Mrs. Cake.

"Am I addressing Mrs. Cake?" said Windle.

"Yes, oi, know," said Mrs. Cake.

"My name's Windle Poons."

"Oi knew that, too."

"I'm a wizard, yoysee -"

"All right, but see you wipes your feet."

"May I come in?"

Windle Poons paused. He replayed the last few lines of conversation in the clicking control room of his brain. And then he smiled.

"That's right, " said Mrs. Cake.

"Are you by any chance a natural clairvoyant?"

"About ten seconds usually, Mr. Poons. "

Windle hesitated.

"You gotta ask the question," said Mrs. Cake quickly. "I gets a migraine if people goes and viciously not asks questions after I've already foreseen 'em and answered 'em."

"How far into the future can you see, Mrs. Cake?"

She nodded.

"Roight, then," she said, apparently mollified, and led the way through the hall into a tiny sitting-room.

"And the bogey can come in, only he's got to leave 'is door outside and go in the cellar. I don't hold with bogeys wanderin' around the house."

"Gosh, it's ages since I've been in a proper cellar," said Schleppel.

"It's got spiders in it," said Mrs. Cake.

"Wow!"

"And you'd like a cup of tea," said Mrs. Cake to Windle. Someone else might have said "I expect you'd like a cup of tea", or "Do you want a cup of tea?" But this was a statement.

"Yes, please, " said Windle. "I'd love a cup of tea."

"You shouldn't," said Mrs. Cake. "That stuff rots your teeth."

Windle worked this one out.

"Two sugars, please," he said.

"It's all right."

"This is a nice place you have here, Mrs. Cake," said Windle, his mind racing. Mrs. Cake's habit of answering questions while they were still forming in your mind taxed the most active brain.

"He's been dead for ten years," she said.

"Er," said Windle, but the question was already there in his larynx, "I trust Mr. Cake is in good health?"

"It's OK. Oi speaks to him occasional," said Mrs. Cake.

"I'm sorry to hear that," said Windle.

"All right, if it makes you feel any better."

"Um, Mrs. Cake? I'm finding it a little confusing. Could you... switch off... your precognition... ?"

She nodded.

"Sorry. Oi gets into the habit of leavin' it on," she said, "what with there only bein' me an' Ludmilla and One-Man-Bucket. He's a ghost," she added. "Oi knew you was goin' to ask that."

"Yes, I had heard that mediums have native spirit guides," said Windle.

" 'Im 'E 's not a guide, "e's a sort of odd-job ghost," said Mrs. Cake. "I don't hold with all that stuff with cards and trumpets and Oo-jar boards, mind you. An' I think ectoplasm's disgustin'. Oi won't have it in the 'ouse. Oi won't. You can't get it out of the carpets, you know. Not even with vinegar."

"My word, " said Windle Poons.

"Or wailin'. I don't hold with it. Or messin' around with the supernatural. It's unnatural, the supernatural. I won't have it."

"Um," said Windle cautiously. "There are those who might think that being a medium is a bit... you know... supernatural?"

"What? What? Nothing supernatural about dead people. Load of nonsense. Everyone dies sooner or later."

"I do hope so, Mrs. Cake."

"So what is it you'd be wanting, Mr. Poons? I'm not precognitin', so you have to tell me."

"I want to know what's happening, Mrs. Cake."

There was a muted thump from under their feet and the faint, happy sound of Schleppel.

"Oh, wow! Rats, too!"

"I went up and tried to tell you wizards," said Mrs. Cake, primly. "An' no-one listened. I knew they weren't going to, but I 'ad to try, otherwise I wouldn't 'ave known."

"Who did you speak to?"

"The big one with the red dress and a moustache like he's trying to swallow a cat."

"Ah. The Archchancellor, " said Windle, positively.

"And there was a huge fat one. Walks like a duck."

"He does, doesn't he? That was the Dean," said Windle.

"They called me their good woman, " said Mrs. Cake. "They told me to be about my business. Don't see why I should go around helpin' wizards who call me a good woman when I was only trying to help."

"I'm afraid wizards don't often listen," said Windle. "I never listened for one hundred and thirty years."

"Why not?"

"In case I heard what rubbish I was saying, I expect. What's happening, Mrs. Cake? You can tell me. I may be a wizard, but I'm a dead one. Schleppel told me it was all due to life force."

"It's buildin' up, see?"

"What does that mean?"

"There's more'f it than there should be. You get" - she waved her hands vaguely ¨C "when things are like in a scales only not the same on both sides..."

"Imbalance?"

Mrs. Cake, who looked as though she was reading a distant script, nodded.

"One of them things, yeah... see, sometimes it just happens a little bit, and you get ghosts, because the life is not in the body any more but it hasn't gone... and you get less of it in the winter, because it sort of drains away, and it comes back in the spring... and some things concentrate it..."

Modo the University gardener hummed a little tune as he wheeled the strange trolley into his private little area between the Library and the High Energy Magic building, with a load of weeds bound for composthood.

There seemed to be a lot of excitement around at the moment. It was certainly interesting, working with all these wizards.

Teamwork, that's what it was. They looked after the cosmic balance, the universal harmonies and the dimensional equilibriums, and he saw to it that the aphids stayed off the roses.

There was a metallic tinkle. He peered over the top of the heap of weeds.

"Another one?"

A gleaming metal wire basket on little wheels sat on the path.

Maybe the wizards had bought it for him? The first one was quite useful, although it was a little bit hard to steer; the little wheels seemed to want to go in different directions. There was probably a knack.

Well, this one would be handy for carrying seed trays in. He pushed the second trolley aside and heard, behind him, a sound which, if it had to be written down, and if he could write, he would probably have written down as: glop.

He turned around, saw the biggest of the compost heaps pulsating in the dark, and said, "Look what I brought you for your tea!"

And then he saw that it was moving.

"Some places, too... " said Mrs. Cake.

"But why should it build up?" said Windle.

"It's like a thunderstorm, see? You know how you get that prickly feelin' before a storm? That's what's happening now."

"Yes, but why, Mrs. Cake?"

"Well... One-Man-Bucket says nothing's dying."

"What?"

"Daft, isn't it? He says lots of lives are ending, but not going away. They're just staying here."

"What, like ghosts?"

"Not just ghosts. Just - it's like puddles. When you get a lot of puddles, it's like the sea. Anyway, you only get ghosts from things like people. You don't get ghosts of cabbages."

Windle Poons sat back in his chair. He had a vision of a vast pool of life, a lake being fed by a million short-lived tributaries as living things came to the end of their span. And life force was leaking out as the pressure built up. Leaking out wherever it could.

"Do you think I could have a word with One ¨C" he began, and then stopped.

He got up and lurched over to Mrs. Cake's mantel-piece.

"How long have you had this, Mrs. Cake?" he demanded, picking up a familiar glassy object.

"That? Bought it yesterday. Pretty, ain't it?"

Windle shook the globe. It was almost identical to the ones under his floorboards. Snowflakes whirled up and settled on an exquisite model of Unseen University.

It reminded him strongly of something. Well, the building obviously reminded him of the University, but the shape of the whole thing, there was a hint of, it made him think of...

... breakfast?

"Why is it happening?" he said, half to himself. "These damn things are turning up everywhere."

The wizards ran down the corridor.

"How can you kill ghosts?"

"How should I know? The question doesn't usually arise!"

"You exorcise them, I think."

"What? Jumpin' up and down, runnin' on the spot, that kind of thing?"

The Dean had been ready for this. "It's spelled with an "O", Archchancellor. I don't think one is expected to subject them to, er, physical exertion."

"Should think not, man. We don't want a lot of healthy ghosts buzzin' around."

There was a blood-curdling scream. It echoed around the dark pillars and arches, and was suddenly cut off.

The Archchancellor stopped abruptly. The wizards cannoned into him.

"Sounded like a blood-curdlin' scream," he said. "Follow me!"

He ran around the corner.

There was a metallic crash, and a lot of swearing.

Something small and striped red and yellow, with tiny dripping fangs and three pairs of wings, flew around the corner and shot over the Dean's head making a noise like a miniature buzzsaw.

"Anyone know what that was?" said the Bursar, faintly. The thing orbited the wizards and then disappeared into the darkness of the roof. "And I wish he wouldn't swear so."

"Come on," said the Dean. 'We'd better see what's happened to him."

"Must we?" said the Senior Wrangler.

They peered around the corner. The Archchancellor was sitting up, rubbing his ankle.

"What idiot left this here?" he said.

"Left what?" said the Dean.

"This blasted wire baskety wheely thing," said the Archchancellor. Beside him, a tiny purple spider-like creature materialised out of the air and scuttled towards a crevice. The wizards didn't notice it.

"What wire baskety wheely thing?" said the wizards, in unison.

Ridcully looked around him.

"I could have sworn ¨C" he began.

There was another scream.

Ridcully scrambled to his feet.

"Come on, you fellows!" he said, limping heroically onwards.

"Why does everyone run towards a blood-curdling scream?" mumbled the Senior Wrangler. "It's contrary to all sense."

They trotted out through the cloisters and into the quadrangle.

A rounded, dark shape was squatting in the middle of the ancient lawn. Steam was coming out of it in little, noisome wisps.

"What is it?"

"It can't be a compost heap in the middle of the lawn, can it?"

"Modo will be very upset."

The Dean peered closer. "Er... especially because, I do believe, that's his feet poking out from under it..."

The heap swivelled towards the wizards and made a glop, glop noise.

Then it moved.

"Right, then," said Ridcully, rubbing his hands together hopefully, "which of you fellows has got a spell about them at the moment?"

The wizards patted their pockets in an embarrassed fashion.

"Then I shall attract its attention while the Bursar and the Dean try to pull Modo out," said Ridcully.

"Oh, good, " said the Dean faintly.

"How can you attract a compost heap's attention?" said the Senior Wrangler. "I shouldn't think it's even got one."

Ridcully removed his hat and stepped gingerly forward.

"Load of rubbish!" he roared.

The Senior Wrangler groaned and put his hand over his eyes.

Ridcully flapped his hat in front of the heap.

"Biodegradable garbage!"

"Poor green trash?" said the Lecturer in Recent Runes helpfully.

"That's the ticket," said the Archchancellor. "Try to infuriate the bugger. " (Behind him, a slightly different variety of mad waspy creature popped out of the air and buzzed away.)

The heap lunged at the hat.

"Midden!" said Ridcully.

"Oh, I say," said the Lecturer in Recent Runes, shocked.

The Dean and the Bursar crept forward, grabbed a gardener's foot each, and pulled. Modo slid out of the heap.

"It's eaten through his clothes!" said the Dean.

"But is he all right?"

"He's still breathing," said the Bursar.

"And if he's lucky, he's lost his sense of smell, " said the Dean.

The heap snapped at Ridcully's hat. There was a glop. The point of the hat had vanished.

"Hey, there was still almost half a bottle in there!" Ridcully roared. The Senior Wrangler grabbed his arm.

"Come on, Archchancellor!"

The heap swivelled and lunged towards the Bursar.

The wizards backed away.

"It can't be intelligent, can it?" said the Bursar.

"All it's doing is moving around slowly and eating things, " said the Dean.

"Put a pointy hat on it and it'd be a faculty member," said the Archchancellor.

The heap came after them.

"I wouldn't call that moving slowly," said the Dean.

They looked expectantly at the Archchancellor.

"Run!"

Portly though most of the faculty were, they hit a fair turn of speed up the cloisters, fought one another through the door, slammed it behind them and leaned on it. Very soon afterwards, there was a damp, heavy thud on the far side.

"We're well out of that," said the Bursar.

The Dean looked down.

"I think it's coming through the door, Archchancellor," he said, in a tiny voice.

"Don't be daft, man, we're all leanin' on it."

"I didn't mean through, I mean... through..."

The Archchancellor sniffed.

"What's burnin'?"

"Your boots, Archchancellor," said the Dean.

Ridcully looked down. A greenish-yellow puddle was spreading under the door. The wood was charring, the flagstones were hissing, and the leather soles of his boots were definitely in trouble. He could feel himself getting lower.

He fumbled with the laces, and then took a standing jump on to a dry flagstone.

"Bursar!"

"Yes, Archchancellor?"

"Give me your boots!"

"What?"

"Dammit, man, I command you to give me your blasted boots!"

This time, a long creature with four pairs of wings, two at each end, and three eyes, popped into existence over Ridcully's head and dropped on to his hat.

"But -"

"I am your Archchancellor!"

"Yes, but -"

"I think the hinges are going," said the Lecturer in Recent Runes.

Ridcully looked around desperately.

"We'll regroup in the Great Hall," he said. "We'll... strategically withdraw to previously prepared positions."

"Who prepared them?" said the Dean.

"We'll prepare them when we get there," said the Archchancellor through gritted teeth. "Bursar! Your boots! Now!"

They reached the double doors of the Great Hall just as the door behind them half-collapsed, half-dissolved. The Great Hall's doors were much sturdier.

Bolts and bars were dragged into place.

"Clear the tables and pile them up in front of the door," snapped Ridcully

"But it eats through wood, " said the Dean.

There was a moan from the small body of Modo, which had been propped against a chair. He opened his eyes.

"Quick!" said Ridcully. 'How can we kill a compost heap?"

"Um. I don't think you can, Mr. Ridcully, sir," said the gardener.

"How about fire? I could probably manage a small fireball, " said the Dean.

"It wouldn't work. Too soggy," said Ridcully.

"It's right outside! It's eating away at the door! It's eating away at the door," sang the Lecturer in Recent Runes.

The wizards backed further away down the length of the hall.

"I hope it doesn't eat too much wood," said the dazed Modo, radiating genuine concern. "They're a devil, excuse my Klatchian, if you get too much carbon in them. It's far too heating."

"You know, this is exactly the right time for a lecture on the dynamics of compost making, Modo," said the Dean.

Dwarfs do not know the meaning of the word "irony".

"Well, all right. Ahem. The correct balance of materials, correctly layered according to -"

"There goes the door," said the Lecturer in Recent Runes, lumbering towards the rest of them.

The mound of furniture started to move forward.

The Archchancellor stared desperately around the hall, at a loss. Then his eyes were drawn to a familiar, heavy bottle on one of the sideboards.

"Carbon," he said. 'That's like charcoal, isn't it?"

"How should I know? I'm not an alchemist," sniffed the Dean.

The compost heap emerged from the debris. Steam poured off it.

The Archchancellor looked longingly at the bottle of Wow-Wow Sauce. He uncorked it. He took a deep sniff.

"The cooks here just can't make it properly, you know," he said. "It'll be weeks before I can get any more from home."

He tossed the bottle towards the advancing heap.

It vanished into the seething mass.

"Stinging nettles are always useful," said Modo, behind him. 'They add iron. And comfrey, well, you can never get enough comfrey. For the minerals, you know. Myself, I've always reckoned that a small quantity of wild yarrow -"

The wizards peered over the top of an overturned table.

The heap had stopped moving.

"Is it just me, or is it getting bigger?" said the Senior Wrangler.

"And looking happier," said the Dean.

"It smells awful," said the Bursar.

"Oh, well. And that was nearly a full bottle of sauce, too," said the Archchancellor sadly. "I'd hardly opened it."

"Nature's a wonderful thing, when you come to think about it," said the Senior Wrangler. "You don't all have to glare at me like that, you know. I was only passing a remark."

"There are times when -' Ridcully began, and then the compost heap exploded.

It wasn't a bang or a boom. It was the dampest, most corpulent eruption in the history of terminal flatulence. Dark red flame, fringed with black, roared up to the ceiling. Pieces of heap rocketed across the hall and slapped wetly into the walls.

The wizards peered out from their barricade, which was now thick with tea-leaves.

A cabbage stalk dropped softly on to the Dean's head.

He looked at a small, bubbling patch on the flagstones.

His face split slowly into a grin.

"Wow," he said.

The other wizards unfolded themselves. Adrenaline backwash worked its seductive spell. They grinned, too, and started playfully punching one another on the shoulder.

"Eat hot sauce!" roared the Archchancellor. 'Up against the hedge, fermented rubbish!"

"Can we kick ass, or can we kick ass?" burbled the Dean happily.

"You mean can't the second time, not can. And I'm not sure that a compost heap can be said to have an -' the Senior Wrangler began, but the tide of excitement was flowing against him.

"That's one heap that won't mess with wizards again," said the Dean, who was getting carried away.

"We're keen and mean and -"

"There's three more of them out there, Modo says," said the Bursar.

They fell silent.

"We could go and pick up our staffs, couldn't we?" said the Dean.

The Archchancellor prodded a piece of exploded heap with the toe of his boot.

"Dead things coming alive," he murmured. "I don't like that. What's next? Walking statues?"

The wizards looked up at the statues of dead Archchancellors that lined the Great Hall and, indeed, most of the corridors of the University. The University had been in existence for thousands of years and the average Archchancellor remained in office for about eleven months, so there were plenty of statues.

"You know, I really wish you hadn't said that, " said the Lecturer in Recent Runes.

"It was just a thought," said Ridcully. "Come on, let's have a look at the rest of those heaps."

"Yeah!" said the Dean, now in the grip of a wild, unwizardly machismo. "We're mean! Yeah! Are we mean?"

The Archchancellor raised his eyebrows, and then turned to the rest of the wizards.

"Are we mean?" he said.

"Er. I'm feeling reasonably mean," said the Lecturer in Recent Runes.