She hurried off. Nanny heard her shoes clattering on the stairs.

Nanny looked down at Walter again, and held out her hand. "Up you get, Walter."

"Yes Mrs. Ogg!"

"I expect we'd better find somewhere for you to lie low, eh?"

"I know a hidden place Mrs. Ogg!"

"You do, do you?"

Walter lurched across the roof toward another trapdoor, and pointed to it proudly.

"That?" said Nanny. "That doesn't look very hidden to me, Walter."

Walter gave it a puzzled look, and then grinned in the way a scientist might after he'd solved a particularly difficult equation. "It's hidden where everyone can see it Mrs. Ogg!"

Nanny gave him a sharp look, but there was nothing but a slightly glazed innocence in Walter's eyes.

He lifted up the trapdoor and pointed politely downward. "You go down the ladder first so I will not see your drawers!"

"Very...kind of you," said Nanny. It was the first time anyone had ever said anything like that to her.

The man waited patiently until she had reached the bottom of the ladder, and then climbed laboriously down after her.

"This is just an old staircase, isn't it?" said Nanny, prodding at the darkness with her torch.

"Yes! It goes all the way down! Except at the bottom where it goes all the way up!"

"Anyone else know about it?"

"The Ghost Mrs. Ogg!" said Walter, climbing down.

"Oh, yes," said Nanny slowly. "And where's the Ghost now, Walter?"

"He ran away!"

She held up the torch. There was still nothing to be read in Walter's expression. "What does the Ghost do here, Walter?"

"He watches over the Opera!"

"That's very kind of him, I'm sure."

Nanny started downward, and as the shadows danced around her she heard Walter say: "You know she asked me a very silly question Mrs. Ogg! It was a silly question any fool knows the answer!"

"Oh, yes," said Nanny, peering at the walls. "About houses on fire, I expect..."

"Yes! What would I take out of our house if it was on fire!"

"I expect you were a good boy and said you'd take your mum," said Nanny.

"No! My mum would take herself!"

Nanny ran her hands over the nearest wall. Doors had been nailed shut when the staircase had been abandoned. Someone walking up and down here, with a keen pair of ears, could hear a lot of things...

"What would you take out then, Walter?" she said.

"The fire!"

Nanny stared unseeing at the wall, and then her face slowly broke into a grin.

"You're daft, Walter Plinge," she said.

"Daft as a broom Mrs. Ogg!" said Walter cheerfully.

But you ain't insane, she thought. You're daft but you're sane. That's what Esme would say. And there's worser things.

Greebo pounded along Broadway. He was suddenly not feeling very well. Muscles were twitching in odd ways. A tingling at the base of his spine indicated that his tail wanted to grow, and his ears definitely wanted to creep up the sides of his head, which is always embarra.s.sing when it happens in company.

In this case the company was about a hundred yards behind and apparently intent on moving his ears quite a long way from their current position, embarra.s.sment or not.

It was gaining, too. Greebo normally had a famous turn of speed, but not when his knees were trying to reverse direction every few seconds.

His normal plan when pursued was to jump onto the water-b.u.t.t behind Nanny Ogg's cottage and rake the pursuer across the nose with his claws when it came around the corner. Since this would now involve a five-hundred-mile dash, an alternative had to be sought.

There was a coach waiting outside one of the houses. He lurched over to it, pulled himself up, grabbed the reins and briefly turned his attention to the driver.

"Get orfff."

Greebo's teeth shone in the moonlight. The coachman, with great presence of mind and urgent absence of body, somersaulted backward into the night.

The horses reared, and tried to break into a gallop from a standing start. Animals are less capable of being fooled than are humans; they knew that what they had behind them was a very large cat, and the fact that it was man-shaped didn't make them any happier.

The coach lumbered off. Greebo looked over his twitching shoulder at the torchlit crowd and waved a paw derisively. The effect pleased him so much that he clambered onto the roof of the swaying coach and continued to jeer.

It is a catlike attribute to spit defiance at the enemy from a place of safety. In the circ.u.mstances it would have been better if catlike attributes had included the ability to steer.

A wheel hit the parapet of the Bra.s.s Bridge and sc.r.a.ped along it, the iron rim kicking up sparks. The shock knocked Greebo from his perch in midgesture. He landed on his feet in the middle of the road, while the terrified horses continued on with the coach rocking dangerously from side to side.

The pursuers stopped.

"What's he doing now?"

"He's just standing there."

"There's only one of him and there's lots of us, right? We could easily overpower him."

"Good idea. On the count of three, we'll all rush him, right? One...two...three..." Pause. "You didn't run."

"Well, nor did you."

"Yes, but I was the one saying 'one, two, three.'"

"Remember what he did to Mr. Pounder!"

"Yes, well, I never liked the man all that much..."

Greebo snarled. Ticklish things were happening to his body. He threw his head back and roared.

"Look, at worst he'd only be able to get one or two of us-"

"Oh, that's good, is it?"

"Here, why's he twisting around like that?"

"Maybe he hurt himself falling off the coach-"

"Let's get him!"

The mob closed in. Greebo, struggling against a morphogenic field swinging wildly between species, punched the first man in the face with a hand and clawed the shirt off another man with something more like a giant paw.

"Oh, shiiiooooo-"

Twenty hands grabbed him. And then, in the melee and the darkness, twenty hands were holding just cloth and emptiness. Vengeful boots connected with nothing more than air. Clubs that had been swung at a snarling face whirled through empty s.p.a.ce and returned to hit their owner on the ear.

"-ooooaaawwwwl!"

Quite unnoticed in the scrum, a flat-eared bullet of gray fur shot out from between the scuffling legs.

The kicking and punching stopped only when it became apparent that all the mob was attacking was itself. And, since the IQ of a mob is the IQ of its most stupid member divided by the number of mobsters, it was never very clear to anyone what had happened. Obviously they'd closed in on the Ghost, and he certainly couldn't have escaped. All that was left was a mask and some torn clothing. So, the mob reasoned, he must have ended up in the river. And good riddance, too.

Happy in the knowledge of a job well done, they adjourned to the nearest pub.

This left Sergeant Count de Tritus and Corporal the Count de n.o.bby n.o.bbs, who lurched to the middle of the bridge and regarded the few sc.r.a.ps of cloth.

"Commander Vimes isn't...isn't...isn't goin' to like dis," said Detritus. "You know he likes prisoners to be alive."

"Yeah, but this one would've been hung anyway," said n.o.bby, who was trying to stand upright. "This way was just a bit more...democratic. A great saving in terms of rope, not to mention wear and tear on locks and keys."

Detritus scratched his head. "Shouldn't there be some blood?" he ventured.

n.o.bby gave him a sour look. "He couldn't've got away," he said. "So don't go asking questions like that."

"Only, if humans is. .h.i.t hard enough, they leaks all over der place," said Detritus.

n.o.bby sighed. That was the caliber of people you got in the Watch these days. They had to make a mystery of things. In days gone by, when it had been just the old gang and an unofficial policy of lazy fair lazy fair, they'd have said a heartfelt "Well done, lads" to the vigilantes and turned in early. But now old Vimes had been promoted to Commander he seemed to be enrolling people who asked questions all the time. It was even affecting Detritus, considered by other trolls to be as dim as a dead glowworm.

Detritus reached down and picked up an eye patch.

"What d'you think, then?" said n.o.bby scornfully. "You think he turned into a bat and flew away?"

"Ha! I do not t'ink that 'cos it is in...consist...ent with modern policing," said Detritus.

"Well, I I think," said n.o.bby, "that when you have ruled out the impossible, what is left, however improbable, ain't worth hanging around on a cold night wonderin' about when you could be getting on the outside of a big drink. Come on. I want to try a leg of the elephant that bit me." think," said n.o.bby, "that when you have ruled out the impossible, what is left, however improbable, ain't worth hanging around on a cold night wonderin' about when you could be getting on the outside of a big drink. Come on. I want to try a leg of the elephant that bit me."

"Was dat irony?"

"That was metaphor."

Detritus, uneasy in what was technically his mind, prodded at the torn pieces of clothing.

Something brushed against his leg. It was a cat. It had tattered ears, one good eye, and a face like a fist with fur on it.

"h.e.l.lo, little cat," said Detritus.

The cat stretched and grinned. "Gerrt lorssst, coppuurrrr..."

Detritus blinked. There are no such things as troll cats, and Detritus had never seen a cat before he'd arrived in Ankh-Morpork and discovered that they were very, very hard to eat. And he'd never heard of them talking. On the other hand, he was very much aware of his reputation as the most stupid person in the city, and he wasn't going to draw attention to a talking cat if it were going to turn out that everybody except him knew that they talked all the time.

In the gutter, a few feet away, there was something white. He picked it up carefully. It looked like the mask the Ghost had worn.

This was probably a Clue.

He waved it urgently. "Hey, n.o.bby-"

"Thank you." Something dipped through the darkness, s.n.a.t.c.hed the mask from the troll's hand, and soared into the night.

Corporal n.o.bbs turned around. "Yes?" he said.

"Er...how big are birds? Normally?"

"Oh, blimey, I dunno. Some are small, some are big. Who cares?"

Detritus sucked his finger. "Oh, no reason," he said. "I am far too smart to be taken in by perfec'ly normal t'ings."

Something squelched underfoot.

"It's pretty damp down here, Walter," said Nanny.

And the air was stale and heavy and seemed to be squeezing the light from the torch. There was a dark edge to the flame.