Melissande groaned. "Well, I'm sure. I'm sure I don't understand a word the two of you are saying. Now start talking Ottish or I swear I'll walk away and let Reg do her worst!"

"Sorry," Monk said, sheepish. "Basically, what it means is I seem to have proven the actual existence of a theoretical construct, which when you think about it is pretty b.l.o.o.d.y exciting, really, even if it's proving a trifle inconvenient, because-"

Melissande grabbed him by both ears and pulled his face towards hers until their noses were touching. "Dearest Monk, I don't care if it's the most exciting thing since the invention of expanding corsets. As far as I'm concerned this sprite of yours is nothing more than a pain in the bu-" She glanced at Reg, who'd perched herself on a handy low-slung palm branch, and smoothly changed tracks. "Nothing more than a huge inconvenience. Incidentally, is it alive?"

With enormous care, Monk disengaged her fingers from his ears then inched himself away from the Botchaki Silk Tree. "I suppose that depends on how you define 'alive'."

"Does it have thoughts? Feelings? Can it communicate?"

"Mel, I don't know," he said. "Honestly. It exists, I know that much. But until I can study it that's all I'm prepared to say."

"And how is it you're so sure we've got it?"

"Oh!" said Bibbie suddenly, and danced a little on the spot. "Of course! Great-uncle Throgmorton's ghost! The sprite's incompatible with our dimension's etheretic vibrations so it's causing physical manifestations on our plane. The housemaids being tossed out of bed and the exploding strawberry syllabub and-"

Monk nodded vigorously. "Exactly!"

"And the ink, Mel," Bibbie added, still dancing. "This explains your debacle with the tamper-proof ink!"

"What debacle with the tamper-proof ink?" said Monk.

Melissande sighed. "I tried to brew up some tamper-proof ink this morning," she muttered, cheeks heating. "And it went kablooey. Three times."

"But now we know it wasn't your fault!" said Bibbie.

"Perhaps if you could manage not to sound quite so surprised?" she said, teeth gritted again. "That would be nice."

"Heh," said Reg, flapping back to her shoulder. "Fat chance of that, ducky."

Bibbie ignored both of them. "It's the only explanation that makes sense. a.s.suming a sprite is an agitation of super-charged inverse etheretic particles with a cohesive substructure in direct reverse proportion to our dimension's thaumaturgical vibrations. Monk?"

"That's the idea, more or less," he said, nodding.

Bibbie slitted her eyes. "Can you come up with a better definition?"

"Ah..." He shook his head. "No."

"Right, then," said Bibbie, and dusted her hands. "That means the sprite's likely to have a particularly deleterious effect on any ambient thaumaturgic processes. In other words-the ink!"

"So I was right," said Monk, vastly relieved. "I knew you had the rotten thing because it's not in the house any more and it's not at work, either, and when I called Mother nothing untoward was happening there so it didn't go home with Dodsworth and the others."

"But why would it have left with us?" said Melissande.

"Well, if my theory on the nature of interdimensional sprites is correct, they're attracted to the corporeal essence of something substantial in their immediate vicinity."

Reg snorted. "Are you quite sure you don't want me to show you those b.u.t.tock-reducing exercises, ducky?"

"Amazing, Monk," said Bibbie, forestalling an imminent outbreak of hostilities. Her eyes were burning with a resurgence of thaumaturgical fervour. "And it's all because you accidentally shifted the polarities of your portable portal prototype."

"Precisely!"

Bibbie threw her arms around her brother and kissed him enthusiastically on both cheeks. "Monk, you're a genius!"

He hugged her back, laughing. "Yeah, well, I dunno-"

"You are, you are! This'll be your second article in The Golden Staff. Oh, I'm so proud of you!"

"Proud of him?" Reg snorted, and gave her tail feathers a peevish rattle. "He's a menace to society, that's what he is." More rattling of tail feathers, and a pointed glare. "And only you could fall a.r.s.e over teakettle for him, Princess Pushy. I'm starting to think you should've fallen for Gerald after all."

Melissande heaved another sigh. There was no point holding a grudge against the horrible bird: Reg made a warthog look thin-skinned. Besides, she had a point. Not about falling for Gerald, but about Monk.

I care for him a great deal, I truly do, but...

"It does sound as though you're playing with fire, you know," she told him. "You really ought to be more careful."

Sometimes he reminded her of a helium-filled balloon: impossible to repress for longer than a few moments. "Mel, trust me, it's perfectly safe," he insisted. "We're not in a skerrick of danger. Not from the sprite, and not from the portal opener. I promise."

How could she doubt him? He was a thaumaturgical genius, after all. "Fine. If you say so."

"I say so," he said, that anarchic grin lighting up his face.

"Yes, well," she muttered, trying in vain to smother her own answering smile. "Only the thing is, aren't you talking theoretically? I mean, I don't suppose you can actually prove any of it, can you? Because if you're right and this sprite creature did leave your place with us last night, I'd like to know for sure."

"And so would I," Bibbie added. "Because I've got some hexes to put together and I don't want them going kablooey."

"As a matter of fact I can prove it," said Monk. "Hold on." He rummaged in the nearby lush tropical undergrowth and pulled out a large, shabby carpetbag. "I threw this together over breakfast. It's a bit rough and ready but I'm pretty sure it'll do the trick."

Melissande frowned as he opened the bag and took out an eye-boggling contraption consisting of a metal rod wrapped in copper wire and attached to some kind of needle-and-gauge arrangement.

"What is it?" she said, suspicious.

His eyebrows shot up. "A portable etheretic sprite detector, of course."

Which he'd invented while eating scrambled eggs and bacon. Of course. She shook her head. "How does it work?"

Monk opened his mouth to answer, then closed it again. "Ah... do you really want me to explain or should I just show you?"

She sniffed. "Good point."

Flicking a switch, he pa.s.sed the wire-wrapped rod down his front. Nothing happened. "See?" he said, grinning again. So ridiculously pleased with himself. Take away his inventions and Monk would go into a decline, she was sure. Just like a baby deprived of its rattle. "No reaction. That means no sprite activity for the last ten hours at least."

Bibbie clapped her hands like a child at a party. "Ooooh, test me, test me!"

Her brother obliged. The needle flickered a couple of times, and the gauge emitted a squeak.

"Ha!" he said. "Contact... but only minimally. You've been in the vicinity of a sprite recently but you haven't had a significant encounter."

"All right then," said Melissande, bracing herself. "Test me."

As Monk ran the sprite detector over her the gauge screeched like a long-tailed cat in a roomful of rocking chairs. Reg let out a shriek and erupted into the humid air, shedding feathers and curses in equal measure.

"Bullseye!" Monk said, practically chortling with satisfaction. "That's excellent. It's always nice to see a theory proven out. You, Melissande, are covered in etheretic spores."

She took a step back. "Etheretic spores? What do you mean etheretic spores? What are etheretic spores?"

"Oh, you know," he said vaguely, checking the readings on the gauge. "Randomly excreted thaumaturgical particles."

Still squawking, Reg landed on a branch of the Botchaki Silk Tree and started a complicated little foot-wiping dance on its pale yellow bark. Horrified, Melissande stared at her outstretched hands.

"Monk, I don't like this!" she said, mortified to hear a quaver in her voice. "I don't like this at-"

"Oh, don't worry," he said blithely, glancing up from his equipment. "I'm pretty sure the spores are harmless."

"Pretty sure? Monk, you raving lunatic, you irresponsible bird brain, you-"

"Oy!" said Reg. "Mind who you're calling a bird brain, madam!"

Monk looked up, surprised. "You're fine, Mel. Really."

"Says you," she retorted. "Forgive me if I'd like a second opinion. After all, you're the one who thought sprites were mythical!"

His face split in another wide grin. "And now we know they're not! Isn't it great? I had no idea that humming three bars of descending cyclonic harmonics in B-flat minor while holding the portal key would get me into other dimensions! If I had I would've gone looking for the one with the voluptuous can-can girls!"

If she'd had a parasol handy she would have poked him in the b.u.t.tocks with it. "Monk Markham, I swear, either you start taking this seriously or-"

"I am taking this seriously!" he protested. "This is a major thaumaturgical breakthrough, Mel, and they don't come along every day. It's fantastic!"

"Fantastic?" Breathless with outrage, she came perilously close to s.n.a.t.c.hing up the carpetbag and throwing it at him. "It's not fantastic, you-you turnip, it's disgusting! I'm covered in interdimensional sprite s.h.i.t! Where's the nearest tap? Has anybody got a clean hanky? How much of the stuff is on me, I can't see a b.l.o.o.d.y thing!"

Monk stared at her, bemused. "Of course you can't. We're dealing with a basic visual incompatibility between dimensional vibrations, remember?"

"No, not really!" she shouted. "I'm a bit too busy being covered in interdimensional sprite s.h.i.t! Where's the wretched thing now, Monk? Is it in my hair?" She began frantically patting her head. "Oh, Saint Snodgress preserve me, don't let there be a sprite in my hair!"

He ran the sprite detector over her again. This time the volume was appreciably lower, more beeping than screeching. "It's okay, it's okay, it's not in your hair, Mel," he said, trying to appease. "It's not anywhere. You're one hundred percent sprite-free, I promise."

"And yet still covered in sprite s.h.i.t, yes?" she demanded.

"Um... well... yes. Sorry about that. But the rate of decay is accelerating," he added encouragingly. "That's good, isn't it?"

She goggled at him. "Decay? You mean I'm covered in decomposing sprite s.h.i.t? How is that good, Monk?"

"It's all right, Mel," said Bibbie, trying to be helpful. "We'll get you cleaned up somehow."

"We certainly will," said Reg from her safely distant tree branch. "The Department's bound to have a decontamination chamber they can spare for a week or two. In the meantime, Mad Miss Markham and I can mind the agency. She'll even remember to collect the mail without being reminded, won't you, ducky?"

"Absolutely," Bibbie agreed. "I promise."

Breathing heavily, Melissande glared at the pair of them. "Strange as it may seem, I don't consider that particularly comforting. In fact I won't be comfortable until we track down this inconvenient creature and send it back where it belongs!" She rounded on Monk. "So if it's not stuck on me, where is it?"

"Still at the agency," said Bibbie. "It must be."

Raising her eyebrows, Melissande flicked a glance at Monk's unhelpful sister. "Must it? How do we know it's not rampaging around town even as we speak?"

"Because there's nothing registering on the Department's monitors," said Monk. "Believe me, I've checked. Besides, if the sprite was loose in town we'd have heard about it by now. Exploding tamper-proof ink would be the least of our worries."

"Then what are you waiting for?" she demanded. "Let's get back to the office so you can catch the little b.u.g.g.e.r and send it packing!"

He winced. "Sorry. I'd love to, only I can't. I've got a secret briefing with Uncle Ralph. But after I invented the portable sprite detector I invented a sprite trap to catch it in. See?"

She stared as he opened the carpetbag again and pulled out what looked like a birdcage for a stunted canary. "It's not very big."

He shrugged. "Neither's the sprite."

"How do you know, Monk? The sprite's invisible!"

"I know," he insisted. "I'm a thaumaturgist, remember?" When she didn't say anything, he adopted a wounded expression. "What? Don't you trust me?"

She gave him an incendiary look. And to think he nagged Gerald for turning Tavistock into a lion... "Of course I do, Monk. When it comes to inventing new ways of getting into trouble I trust you implicitly."

Reg sn.i.g.g.e.red. "You tell him, ducky."

"And speaking of invisible," she added, "since we can't see this wretched sprite, how exactly are we supposed to catch it?"

"Easy," said Monk, so effortlessly confident. So completely unmoved by her righteous indignation. He was the most infuriating man... "There's an etheretic normaliser built into the trap. You activate it with this switch here, see?" He pointed. "If the sprite's within range the multi-phase thaumaturgic agitation will render it visible."

"For how long?"

"Long enough, I promise."

"And how do you define "within range"?"

"A few feet."

"Is that all?" she said, dismayed. "Monk-"

"I know, I know," he said, carelessly apologetic. Infuriating? He was impossible. "Sorry, Mel. What can I say? It was a rush job."

As solutions went it was far from perfect, but with time and circ.u.mstances against them it would have to do. "Fine. And what happens once we've caught our uninvited guest?"

"You can leave me a message at the Department and I'll drop by the agency and pick it up," said Monk. "Better yet, come to dinner tonight and bring it with you."

She stared at him. He was serious. He was actually, deadly, serious. If I wasn't in lo-quite fond of him, I really would punch him in the nose. "Monk-"

"Oh, save your breath, ducky," said Reg, and flapped down from the tree branch to take up her favoured shoulder-perch. "Let's just take care of this, shall we? I don't know about you but I want a bath!"

"One bath?" Melissande stared down at her invisible-sprite-s.h.i.t-covered self. "I won't be getting out of the tub for a week! I don't care how many times I have to tramp up and down those stairs with kettlefuls of hot water!"

"Does that mean you'll do it?" her infuriating, impossible young man asked hopefully.