'The trouble is, you see, that if you do know Right from Wrong you can't choose Wrong. You just can't do it and live. So... if I was a bad witch I could make Mister Salzella's muscles turn against his bones and break them where he stood... if I was bad. I could do things inside his head, change the shape he thinks he is, and he'd be down on what'd been his knees and begging to be turned into a frog... if I was bad. I could leave him with a mind like a scrambled egg, listening to colours and hearing smells... if I was bad. Oh, yes.' There was another sigh, deeper and more heartfelt. 'But I can't do none of that stuff: That wouldn't be Right.'

She gave a deprecating little chuckle. And if Nanny Ogg had been listening, she would have resolved as follows: that no maddened cackle from Black Aliss of infamous memory, no evil little giggle from some crazed vampyre whose morals were worse than his spelling, no side­splitting guffaw from the most inventive torturer, was quite so unnerving as a happy little chuckle from a Granny Weatherwax about to do what's best.

From the point of her hat Granny withdrew a paper‑thin mask. It was a simple face–smooth, white, basic. There were semi‑circular holes for the eyes. It was neither happy nor sad.

She turned it over in her hands. Walter seemed to stop breathing.

'Simple thing, ain't it?' said Granny. 'Looks beautiful, but it's really just a simple bit of stuff, just like any other mask. Wizards could poke at this for a year and still say there was nothing magic about it, eh? Which just shows how much they know, Walter Plinge. '

She tossed it to him. He caught it hungrily and pulled it over his face.

Then he stood up in one flowing movement, moving like a dancer.

'I don't know what you are when you're behind the mask,' said Granny, 'but "ghost" is just another word for "spirit" and "spirit" is just another word for "soul". Off you go, Walter Plinge.'

The masked figure did not move.

'I meant... off you go, Ghost. The show must go on.'

The mask nodded, and darted away.

Granny slapped her hands together like the crack of doom.

'Right! Let's do some good!' she said, to the universe at large.

Everyone was looking at her.

This was a moment in time, a little point between the past and future, when a second could stretch out and out...

Agnes felt the blush begin. It was heading for her face like the revenge of the volcano god. When it got there, she knew, it would be all over for her.

You'll apologize, Perdita jeered.

'Shut up!' shouted Agnes.

She strode forward before the echo had had time to come back from the further ends of the auditorium, and wrenched at the red mask.

The entire chorus came in on cue. This was opera, after all. The show had stopped, but opera con­tinued...

'Salzella!'

He grabbed Agnes, clamping his hand over her mouth. His other hand flew to his belt and drew his sword.

It wasn't a stage prop. The blade hissed through the air as he spun to face the chorus.

'Oh dear oh dear oh dear,' he said. 'How extremely operatic of me. And now, I fear, I shall have to take this poor girl hostage. It's the appropriate thing to do, isn't it?'

He looked around triumphantly. The audience watched in fascinated silence.

'Isn't anyone going to say "You won't get away with this"?' he said.

'You won't get away with this,' said André, from the wings.

'You have the place surrounded, I have no doubt?' said Salzella brightly.

'Yes, we have the place surrounded.'

Christine screamed and fainted.

Salzella smiled even more brightly.

'Ah, now there's someone operatic!' he said. 'But, you see, I am going to get away with it, because I don't think operatically. Myself and this young lady here are going to go down to the cellars where I may, possibly, leave her unharmed. I doubt very much that you have the cellars surrounded. Even I don't know everywhere they go, and believe me my knowledge is really rather extensive­'

He paused. Agnes tried to break free, but his grip tightened around her neck.

'By now,' he said, 'someone should have said: "But why, Salzella?" Honestly, do I have to do everything around here?'

Bucket realized he had his mouth open. 'That's what I was going to say!' he said.

'Ah, good. Well, in that case, I should say something like: Because I wanted to. Because I rather like money, you see. But more than that'‑ he took a deep breath–'I really hate opera. I don't want to get needlessly excited about this, but opera, I am afraid, really is dreadful. And I have had enough. So, while I have the stage, let me tell you what a wretched, selfadoring, totally unrealistic, worthless artform it is, what a terrible waste of fine music, what a–'

There was a whirr off on one side of the stage. The skirts of costumes began to flap. Dust flew up.

André looked around. Beside him, the wind machine had started up. The handle was turning by itself.

Salzella turned to see what everyone was staring at.

The Ghost had dropped lightly on to the stage. His opera cloak billowed around him... operatically.

He bowed slightly, and drew his sword.

'But you're dea–' Salzella began. 'Oh, yes! A ghost of a Ghost! Totally unbelievable and an offence against common sense, in the best operatic tradition! This was really too much to hope for!'

He thrust Agnes away, and nodded happily.

'That's what opera does to a man,' he said. 'It rots the brain, you see, and I doubt whether he had too much of that to begin with. It drives people mad. Mad, d'you hear me, mad!! Ahem. They act irrationally. Don't you think I've watched you, over the years? It's like a hothouse for insanity!! D'you hear me? Insanity!!'

He and the Ghost began to circle one another.

'You don't know what it has been like, I assure you, being the only sane man in this madhouse!! You believe anything!! You'd prefer to believe a ghost can be in two places at once than that there might simply be two people!! Even Pounder thought he could blackmail me!! Poking around in places that he shouldn't!! Well, of course, I had to kill him for his own good. This place sends even ratcatchers mad!! And Undershaft... well, why couldn't he have forgotten his glasses like he usually did, eh?'

He lashed out with his sword. The Ghost parried.

'And now I'll fight your Ghost,' he said, moving forward in a flurry of strokes, 'and you'll notice that our Ghost here doesn't actually know how to fence... because he only knows stage‑fencing, you see... where the whole point, of course, is simply to hit the other fellow's sword with a suitably impressive metallic noise... so that you can die very dramatically merely because he's carefully thrust his sword under your armpit...'

The Ghost was forced to retreat under the onslaught, until he fell backwards over the unconscious body of Christine.

'See?' said Salzella. 'That's what comes of believing in opera!!!'

He reached down quickly and tugged the mask off Walter Plinge's face.

'Really, Walter!!! You are a bad boy!!!!'

'Sorry Mr Salzella!'

'Look how everyone's staring!!!!'

'Sorry Mr Salzella!'

The mask crumpled in Salzella's fingers. He let the fragments tumble to the floor. Then he pulled Walter to his feet.

'See, company? This is your luck!!! This is your Ghost!!! Without his mask he's just an idiot who can hardly tie his shoelaces!!! Ahahaha!!!! Ahem. It's all your fault, Walter Plinge...'

'Yes Mr Salzella!'

'No .'

Salzella looked around.

'No one would believe Walter Plinge. Even Walter Plinge gets confused about the things Walter Plinge sees. Even his mother was afraid he might have murdered people. People could accept just about anything of a Walter Plinge.'