The sooty hairball spoke quickly, as if eager to convince Arthur of its story. As it spoke, it slowly unravelled, becoming less of a ball and more like a hairy, sooty slug. A very big hairy, sooty slug.

‘More than nine thousand years ago I was one of Grim Tuesday’s eyebrows, before I was wrenched from his forehead by an explosion of Nothing, down in the first, dark diggings of the Pit. I was lost there for centuries, next toNothing. Slowly the emanations ofNothing transformed me and I became a thinking, living creature. Neither a Denizen made by the Architect, nor a Nithling born out of Nothing. The true Nithlings despise me and the Denizens fear me. Both attempt to slay me at any opportunity.’

Suzy and Arthur looked at each other, then back at the hairy slug. It did resemble a vastly overgrown, animate eyebrow. A long, hairy crescent, caked in soot. It moved back a little under their combined stares, undulating sideways and making faint popping sounds.

‘I am still attuned to Grim Tuesday,’ declared the thing. ‘I know some of his mind and secrets.’

‘It does look like a huge eyebrow,’ said Suzy hesitantly. ‘And strange things do happen near lots of Nothing.’

‘What are you doing up here?’ asked Arthur. He wished he could consult the Atlas and check up on this . . . eyebrow . . . but it was too difficult in his present situation.

‘I’ve been trying to get in the Treasure Tower,’ said the thing. ‘I need to be near the treasures. I want to feel the weight of the gold, bathe in the reflected light of the paintings, embrace the statues. Once I get in, I shall never leave. That’s all I want – to get in the Treasure Tower!’

‘If you can’t get in yourself, how can you help us?’ asked Arthur.

‘I cannot get in by myself,’ said the blob, ‘but I can help you, and then you can help me. For example, I have a diamond to cut the glass.’

‘Show it to us, then,’ Suzy demanded.

The blob undulated backwards and forwards, popping unpleasantly, and opened its mouth wider than Arthur would have thought possible. A black, sticky-looking tongue slowly poked out. Coiled up in the end of the tongue was a diamond as big as Arthur’s thumbnail, sparkling in the light from the ceiling.

‘Where did you get that?’ asked Suzy.

‘I madth ith,’ the blob started to say, then it withdrew its tongue and continued. ‘I made it from Nothing. I told you, I know much that the Grim knows. I also have some of his talents. But my tongue is not strong enough to hold the diamond and cut the glass. I need a hand.’

‘What’s your name?’ asked Arthur. When the blob didn’t answer for a moment, he added, ‘What do you call yourself?’

‘I suppose you could call me . . . Soot,’ said the thing. ‘Yes . . . Soot. I have breathed it, lived in it, and eaten it for so long that it is a fitting name.’

‘Eaten it?’ asked Suzy. ‘Why eat soot?’

‘Boredom,’ said Soot. ‘The Overseers fire their steam-guns at me if I get too close. The Nithlings would eat me themselves. I have been unable to get into the Treasure Tower. What else has there been for me to do but brood upon the walls and ceiling of this realm and eat soot?’

‘If we help you get into the Treasure Tower,’ said Arthur, ‘you’ll have to swear to help us in every way you can against Grim Tuesday.’

‘Yes!’ cried Soot. It practically bounced off the ceiling in excitement. Arthur wished it hadn’t because he saw its belly, lined with lots of horrid-looking little suckers, like an octopus’s tentacle. That was what made the popping sound when it moved.

‘That story might be true, but I reckon that still makes it a Nithling,’ whispered Suzy, as she edged as close as she could to Arthur. ‘A clever one, so very dangerous. But we need that diamond.’

‘I’m sick of hanging upside down and getting smashed into . . . this stupid ceiling,’ Arthur whispered back. ‘Let’s accept its help for now.’

Suzy nodded reluctantly.

‘We accept your offer,’ said Arthur to Soot.

‘Fine! Fine!’ burbled Soot. ‘It’s a pleasure working with you. Whoever you are.’

‘I’m Arthur,’ said Arthur quickly, before Suzy could introduce him as Monday or the Master of the Lower House. ‘That’s Suzy.’

‘And you’ll be thieving just a few odds and ends from the Treasure Tower?’ asked Soot. His voice sounded slightly anxious and he clearly took it for granted that Arthur and Suzy were thieves.

‘We’ll be reclaiming stolen goods!’ snapped Suzy indignantly. ‘Goods as should have been returned to their rightful owner ten thousand –’

‘Suzy!’ interrupted Arthur. He didn’t want Soot to know too much. If the thing did have some strange connection with Grim Tuesday, it was possible that Grim Tuesday might have a connection with it, as well.

‘Reclamation,’ muttered Suzy. ‘Arthur only wants wot he’s supposed to have already –’

‘Suzy! Are you ready to do the stickit spell?’

‘Oh, stickit fingers, is it?’ asked Soot, peering with his silvery eyes atArthur’s hands. ‘Very nice workmanship.Not made by the Grim himself, but one of his better crafters.’

‘Stick by day and stick by night, stick for a minute each, left and right,’ Suzy recited to her hands, keeping herself propped on her elbows and forearms. As she said the words of the spell, the little finger puppet things on her fingers wriggled and squeaked and began to glow with a fuzzy green light.

Suzy braced against a wingbeat, then slapped both hands against the ceiling and pulled back. One hand stuck by the thumb and two fingers. Immediately Suzy used her other hand to grab both strings that hung around her neck. She pulled them. Wax seals cracked and her two wings instantly blew into a cloud of confetti that was whisked away by the breeze.

Suzy hung from the ceiling and turned to Arthur. She smiled, despite her two black eyes and a bruise on her chin, evidence of the damage done by being constantly beaten into the ceiling.

‘That’s a relief! I’ll be dropping in about forty seconds, so you jump now, Mister Soot, and make sure you keep your distance on the pyramid.’

Suzy punctuated her instruction by drawing the copper tube out of her belt.

Soot needed no encouragement.With a single flexing motion, accompanied by lots of tiny popping noises like exploding bubble wrap, it launched itself straight down. Caught a little by the breeze, it plopped onto the eastern face of the pyramid, about thirty feet below the apex.

‘Good luck, Arthur,’ said Suzy. She quickly thrust the copper tube back through her belt to leave her hand free. ‘I reckon you should –’

The stickits on her right hand suddenly stopped squeaking and sticking.

Arthur watched Suzy fall. He almost couldn’t bear to see her hit the pyramid, but she landed on her feet, then bounced and rolled down for a few seconds before she arrested her descent by slapping her sticky left hand on the glass.

She lay still for a few seconds, then rolled back and waved up at Arthur, shouting something he couldn’t hear, the words carried away by the breeze and the beat of his wings.

Arthur looked back up, stopped himself yet again from being pushed into the ceiling, and took a deep breath. Then, propping himself so his hands didn’t touch the ceiling, he spoke the words of the stickit finger spell.With the last word, he felt the ends of his fingers tingle, and the stickits on his left hand began to squeak.

Arthur used his right hand to pull the right string. He heard the wax crack, then confetti blew up past his ears. A second later, he began to fall, while his remaining wing beat harder and harder, trying to maintain its single-minded upwards thrust.

Arthur expected to corkscrew, but he didn’t. Instead his single wing threw him head over heels, which rapidly became a series of wild somersaults.

An eye-blink later, Arthur hit the glass face of the pyramid.

Very, very hard.

THIRTEEN

ARTHUR SCREAMED as he hit. There was an unbearable pain in his left leg, and he was sliding down the glass, faster and faster, while his single wing thrashed around his head so he couldn’t see anything.

Then he managed to slap his sticky hand on the glass and came to a sudden stop. He pulled the string and almost choked on a sudden mouthful of confetti as it shot up all around him.

Arthur started to slide again as his hand became unstuck. He slapped his other hand down and stopped again.He could hear Suzy shouting something, and Soot too, but couldn’t give themany attention.He had to see what was wrong with his leg. The pain was deep inside, but stabbing up into his body and down to his feet. He hardly dared to look.

But he made himself. Both his jeans and the pyjama-like trousers the Lieutenant Keeper had given him were ripped. He could see some blood and what he had feared – something protruding that could only be bone.

He’d broken his tibia or fibula, the bones in the lower leg.Maybe both of them, in a complex fracture. A bad one.

Arthur felt a terrible, sudden coldness sweep over him. He began to shiver. He tried to quell the shivers as he drew his leg up for a closer look. It made him feel sick to see his leg looking all lumpy and wrong, with that piece of bone thrust out through the skin.

Arthur gulped in a deep breath. He could feel his lungs tightening as panic set in.

I will not have an asthma attack, he told himself. I can’t have one. I’m in the House. Things are different here. Everything heals quickly. Even a broken bone will heal in time . . . but I haven’t got time . . . can’t stand the pain for long . . . I have to do something . . .

Hesitantly, he laid his hand lightly over his shin, only just touching the lumpy broken part. Even so, it sent another stab of pain up his leg and into his head. He almost blacked out.

‘By the power of . . . of the First Key . . . the power that remains in my hand,’ Arthur whispered. ‘Heal me. Fix the broken . . . bone.’

His hand stopped shaking, though the rest of his body didn’t. Then he felt it grow hot. As Arthur watched, the bone retreated back through the skin, which rejoined itself.

The pain remained for what seemed like several minutes but could only have been seconds, for it faded just as Arthur’s right hand lost its stickiness and he had to slap his left hand onto the glass.

His leg still felt very strange, but Arthur was able to look around and refocus on what was going on. A moment later Suzy slid down next to him, stopping herself a little short with her sticky hand. Soot watched from a distance, silver eyes twinkling amid its black hair.

‘What happened?’ asked Suzy. ‘Are you sorely hurt?’

Arthur shook his head. The shakes were slowly subsiding but it took an effort to find his voice.

‘I . . . I broke my leg. But I think I fixed it . . .’

Suzy raised her eyebrows and grimaced when it made her black eyes hurt.

‘Not bad. Don’t s’pose you could fix up my bruises while you’re at it?’

‘Uh, I don’t really know what I did,’ said Arthur. He lifted his leg and flexed it a few times. It felt stiff and clumsy, and Arthur experienced a stab of fear. The bone was healed all right, but his leg now looked and felt a bit crooked.

It hasn’t set straight, he thought. I’ll be lame. No running ever. No baseball. No soccer.

‘Uh-oh,’ said Suzy, interrupting Arthur’s thoughts. ‘Overseers.’

Arthur looked down and started to slip. Quickly he changed hands again and temporarily forgot about his leg. Suzy was pointing to a band of Overseers that had emerged out of the smog down below and were running towards the base of the pyramid.

‘Don’t think their steam-guns’ll reach us,’ said Suzy. ‘But they might have other weapons. We’d better start. It won’t be quick with the stickit fingers.’

‘Yes! Yes!’ called out Soot. It started undulating to the top of the pyramid. ‘We must get inside and join . . . see the treasures!’

Arthur nodded and pulled himself up as far as he could above his sticking hand and reached out to plant his other hand. Then he had to wait until it stuck, then repeat the process.

After ten minutes, they were still short of the top. Almost a thousand feet below and several hundred feet to the east, at the base of the pyramid, the group of Overseers was busy putting together something that looked suspiciously like a weapon. They had wheeled a steam engine in from somewhere out in the smoggy regions and were stoking it furiously, as other Overseers set up a long bronze barrel on a tripod mount and connected it to the engine by a hose of some silver-metal mesh.

‘Steam-cannon,’ said Soot, looking down from its perch on the very apex of the pyramid. ‘Hurry, before they blast us off!’

‘We are hurrying!’ saidArthur as he pulled back on one hand to see if it was sticking yet.He kept looking down, not at the Overseers, but at his leg. As far as he could tell, it worked fine, but froma point several inches below his knee the leg was definitely not straight and it felt weird.

Suzy reached the top before Arthur. Soot immediately held out the diamond in his tongue

‘Wait,’ said Suzy. ‘I’ll have to time my stickits carefully.’

She took out her pocket watch, left it hanging down the front of her apron, and waited till her stickit fingers swapped. Then she extracted a once-white handkerchief from her sleeve, used it to receive the gem, and gave it a good polish before she touched it.

‘Keep an eye on my watch,’ she instructed Arthur as he arrived. ‘I’ll cut till my stickit fingers are about to swap. Tell me when the second hand hits two.’

Arthur looked at the watch dangling on its silver-gilt chain. It kept spinning around, so the face was difficult to see. The second hand was ticking around steadily, but as it reached twelve Arthur was distracted by his own stickits swapping over.