"I'm flattered and, really, I'm intimidated. But come on guys, you're dealing with a damned soul here." A pause and a sickening smirk. "I'm not saying your good cop, bad cop thing is lame, but you have to admit it's hard to compete with the sufferings of Hades. Do your worst. I'm not saying anything!" The speaker laughed.

"We don't want you to talk, Knox. In fact, stop talking." Angel was tensed, as enraged as Spike had ever seen him. His fists clenched.

Knox. The weasel beamed at them, all little boy and cute-as-you-like. Spike had already thought of several inventive ways to wipe that smile away. He wished there weren't bars separating them. For someone who'd been taken from hell's torments, Knox wasn't too grateful or cooperative. No way was he going to be getting these Duracells of Blue's. But then, she hadn't arrived yet to ask him nicely.

"Hey, I aim to please." Smiler made a zipping motion across his lips. Bastard.

Trying to maintain a cold expression, Spike stepped outside, dragging Angel with him. In the corridor he allowed his attempt at a sinister sneer to slip. Hopeless. They weren't going to get any anywhere like this. A good job they had an ace. Or a queen. Or a king. Spike shrugged, dismissing the fruitless encounter. "He'll soon change his tune when Blue gets here."

Angel's fists relaxed a little. Just a little. "What makes you say that?" There was an atmosphere of violence and stillness in the air. An echo of the old days.

"He's her Kwa Ha what's-it. He worships her."

"Qwa'ha Xahn. Qwa'ha. Wes said it was sort of a glottal stop." Angel gazed at the corridor's exit, eager to get away by the looks of it. Could be he was feeling the demon inside growing restless. "Knox wouldn't want to see Illyria put back in her box. He sacrificed everything to get her, it, out of the Well." His brow lowering, Angel glanced to one side. "And we were doing good cop, bad cop?"

"Well, yeah. I thought you knew."

"I'm the bad cop, right?"

"I'm the bad cop." As bad as they come. "You know, this would have been much easier back in the day. Nina in LA yet?"

Surprise showed itself on the other vampire's face. "Last week. Why?"

"She's almost due for her monthlies. We could make Knox and her cellmates." Spike felt himself grin, not-too-soulfully. "Just a thought."

The boss gave him a look that was hard to read. "We can't torture him, Spike. It's not even an emergency."

Torture? It was all relative. Not much of a leap from harsh language to the thumbscrews. "No torture. Just put the fear of God into him. Give me a few minutes."

Now Angel smiled, not very differently from the way Angelus used to. "I'll be in my office if you need me." And off he went, hands washed clean.

Fair enough. Spike opened the door and went back into the cells. "Just you and me, then," he told Knox. "Nice and cosy." Leaning back against the wall, he folded his arms and tried to match the man's repugnantly cheerful expression. "Up the close and down the stair."

Knox's eyes twinkled boyishly. "Huh?"

"In the house with Burke and Hare."

Amazed laughter from Smiler now. Self-consciously amazed laughter. "What does that mean? Are you trying to scare me?" He shook his head and wagged a finger. "Uh uh. I know all about you, Spike."

"Do you, now?"

The happy mask slipped a bit, showed up some of the rottenness beneath. "Yes. I do. You're a soul man. You won't hurt a human. Really? It's pathetic." He opened his mouth to say something else, but stopped when the bad cop produced an object from his duster. Spike dropped this item. It hit the floor with a dull, metallic bang.

"First of all, Knox, you aren't human. Don't flatter yourself." Spike removed another object and let it fall. The sound stabbed through the small room. "Second, you're dead, anyway. I'm thinking that makes you fair game." A final object joined the others on the ground. "Third…" What was third? After a moment's consideration, he said simply, "You're a wanker."

For the first time, Knox looked scared. All that talk of the sufferings of Hades must be a bluff. He was probably on the fast track down there, playing with brimstone in his chemistry set. "What are those?"

"Looks like you don't know me all that well." The railroad spikes were brutally real in the half-light of the cells. Smiler wasn't smiling now. Even for a dead man, he looked pale. This was going to be easier than Spike had thought. It felt good to see so much fear, to know he was the cause. Wait a minute, why was Knox looking at something to the left? Spike span around, amazed he hadn't heard the door open or close.

"Hi, Knoxy," Illyria said. She didn't look like Illyria. Brown hair and eyes, peaches and cream skin, glasses, lab coat – every inch the nerdy science girl. If Wes was here he would have been panting. Grinning, quirky, she took a step forward, not quite impulsive. Blue had really got good at this. You had to wonder just how much of it was an act. That was the question these days, wasn't it?

"I trusted you, Knox. I thought you were nice."

Knox gaped at her.

"It was slow and it hurt. It hurt so much." The grin fell and, almost violently, her appearance changed to blue and black. A dawning look of relief on Knox's face vanished as Illyria wrenched the cell door out of its frame and grabbed him by the throat. "You condemned me to live in this shell, diminished, in this place."

He started to splutter. "Hey! Sorry!"

"Wesley has been in agony. It is your doing." Her grip tightened.

There was some bafflement in Knox's eyes. He probably wondered why she cared what Wes was feeling. But he didn't say anything. Couldn't, not with that much pressure on his windpipe.

It might be an idea to cool this down. Spike laughed, a little nervously. "Look, love-"

Her face darted in his direction, eyes like frozen suns. "I do not want your cocoa." Maybe that should have been funny, but it wasn't. Weird talk of hot beverages aside, she was frightening now. Really frightening. Turning back to Knox, she relaxed her fingers slightly. "You will retrieve my sacraments, Qwa'ha Xahn."

After sucking in a breath, Knox started spluttering again. "No! That's what they want. The vampires, the humans, the demon. They'll use the sacraments against you."

"They are my allies." A horrible gentleness crept into her tone. "For now I confer mercy, but if you presume to debate with me I will see to it that you pay for what you have done. In full. Your screams will be panicked birds taking wing in the dark forest of your anguish. I will shape a misery for you that knows no limitations. I will-"

The theme music to The Simpsons drifted across the room.

Illyria and Knox stared at Spike. He closed his eyes, pinched the bridge of his nose between thumb and finger, and then reached into a pocket for his cell phone. That ring tone had to go. The phone's screen had the words "FOREHEAD BOY" on it.

Spike punched a button to receive the call and brought the phone to his mouth. "Guess what? I'm in the middle of something."

"Quiet," Angel hissed.

That sounded bad. Hushing himself to a level that even Blue might have trouble hearing, Spike said as casually as he could, "Alright."

Angel's voice was urgent. "Illyria."

She still stared, still with one hand around Knox's throat. Spike turned his back on her. "She's here. You want me to put her on?"

The other vampire groaned softly. "I'm coming down there. Keep her the hell away from Knox."

Risking a quick glance over his shoulder – Knox was being half-throttled – Spike tried to sound innocent. "Why?"

Corridor chatter formed a background of noise on the phone. Angel must be moving through the building. "I just got a call from the mind-enhancement clinic. According to the security cameras, Illyria was there all last night. It looks like she killed Sparrow."

"Looks like?"

"No one's been able to ID what she left behind."

Hell. A psycho god on the loose. That was nice news for a Wednesday evening. After what he'd seen her do, it was no surprise to Spike that she could reduce a human body to jam. Even so… "Teeth? Fingerprints?"

The door opened, and Angel rushed into the room, pocketing his phone. "There's just a mess. Let him go." He aimed this latter comment at Illyria.

"I will not." She was as serene as a breeze.

After entering the cell, Angel brought his face to within a few inches of hers. Pushing his luck. "Let him go and back off."

Had Spike thought she was scary? She bared her teeth – now she was scary. It seemed like she was going to have it out with Angel right there. But then something inside her gained control. Her fingers slipped from Knox and she became tranquil again. "I would not harm him, not when he is of use to me."

A mocking expression formed on Angel's features. "Is that why you murdered Sparrow, because he wasn't of use?"

Unfazed, she gestured to something. It might have been the room, the world, or the universe. "I brought about what had to be. The slaughter of monsters is your business, is it not?"

"Yes, but…" A patient sigh from Angel. "We've been through this. A human can be redeemed. I'd be the first to admit Sparrow was slime, but he was human."

Illyria did that almost smile of hers. "It degrades humanity to label him such. Angel, would you also call the deadly ice life-giving water?"

Not bad. That was worth writing down.

"Wait," said Knox. "You killed Sparrow?"

"Shut up, Knox." Angel seemed affected by Illyria's words. Maybe he was just surprised she'd used his name. His eyes locked with hers, searching. "Who am I really talking to, here?"

Apparently losing interest, Illyria looked at Knox again. "Wrong, right – this morality does not apply. There is only necessity. Serve me, Qwa'ha Xahn. We are journeying to the repository of your shell." She gripped his arm and led him from the room.

Staring after them, Angel frowned slightly. He looked more pensive than angry, and he'd definitely had the self-righteousness knocked out of him. The latest crisis was over, apparently. A few seconds passed and then he motioned toward Illyria's and Knox's retreating backs. "Go with them."

Rolling his eyes in resignation, Spike followed the Old One and her priest. Nursemaid duty again.

- - -

4.6692016091029906718532038…

Papers were strewn around Fred's apartment, an outward sign of Wesley's perplexity. One number, the value of the quantity δ, appeared frequently in Illyria's article. It was pivotal in many equations and was the "delta constant" so often referred to in the accompanying text. After calculating it to twenty-five decimal places, Wes had stopped. Quite probably the number was transcendental, and the places extended to infinity.

Wesley put down the page he'd been reading and made yet another circuit of the apartment. Among the framed pictures on the walls were some of Fred's favourite equations, also framed. She'd told him she liked to see them because they were certain and ordered. They even brought chaos under their control.

In the article, δ played an important role in the bifurcation – the dividing into two halves – of atomic energy states. What that exact role was, however, was difficult to determine. The ideas presented were so far-reaching that Wes had problems grasping them for long enough to reach a final understanding. Whenever the eureka moment began, it ran away from his comprehension once more. The article was a mongrel born of different, and sometimes competing, models. It contained various interpretations of quantum mechanics, chaos, superstrings, supergravity, and supersymmetry.

"Give me a clue, Fred," Wesley whispered. In desperation he went to the personal effects from her office at Wolfram & Hart. Perhaps there was a note scrawled somewhere on a post-it, a writing pad, the Dixie Chicks poster, anything. Squatting, opening the box containing her things, he was immediately overwhelmed with emotion. He allowed himself a moment to experience it. His fingers moved lovingly over her glasses, and he wondered if he would see her wearing them soon. They were the only things that had gone to Pylea and back with her. He examined them. No scratches or marks.

Her toy rabbit wore glasses of its own; this for some reason made Wes pick it up. He smiled, playing with the floppy ears. It was a handsome little chap. As Wesley turned it over in his hands, he caught a trace of Fred's perfume and involuntarily brought the toy closer to his face. That was when he noticed some letters, almost faded away, on a label sticking out from the rabbit's leg. The handwriting was unformed and lacked the character it would later take on – a child's writing – but it was unmistakably Fred's. "Feigenbaum," it said.

That was the name she'd called out in her pain and fear. So it was this, obviously a cherished childhood toy, that she'd desperately needed. It might have comforted her, as his reading from A Little Princess had done. Wes put the rabbit down. Standing, he took several slow, deep breaths before he moved to a corner of the room. There was, perhaps, one more thing he could try.

While the PC booted, Wesley sat and considered his dwindling options. He'd already checked every file on Fred's hard drive, and nothing new had turned up. There was just the internet left. After going online, he typed the first six digits of δ into Google and pressed Enter, expecting nothing. There were three hundred and forty-two hits. He straightened, scanning the summaries of the first ten results. Feigenbaum was mentioned five times. Sliding forward so suddenly he almost fell from his chair, Wesley opened another two browser windows and began to investigate more seriously, cross-referencing Boolean search terms. A few minutes later, he knew Feigenbaum's life story. He even had his email address.

Mitchell Feigenbaum was a professor at the Rockefeller University. He was known as a mathematician, primarily a chaos theoretician, but he personally saw no distinction between mathematics and physics, as if the science of the abstract and the science of the physical were one and the same. Although Feigenbaum considered chaos to be erratic and unpredictable, he posited chaotic motion as lying within an intricate subspace, known as a complex set or strange attractor, where its various possibilities were limited and its true nature hidden. The only way such systems could be studied was through methods of observation that built up complex details. Fractals, in other words.

Opening a source book, Wes said, "All published works by Mitchell Feigenbaum, with references to bifurcation and the delta constant highlighted, annotated to include commentary by secondary sources." He began to speed-read.

The delta constant had first appeared in print in 1979. Fred would have been four or five years old. Transcendental and also known as the Feigenbaum constant and the Feigenbaum number, it was the ratio between successive bifurcations in the Mandelbrot fractal set. But it had taken on more significance than this. Some careful searching of the annotations revealed that the constant had been used in equations describing the transition of electrons from one atomic shell to another. So the constant could be a sort of bridge between deterministic chaos theory and non-deterministic quantum mechanics.

The mists weren't parted so much as blown aside by a gale of knowledge. In Wesley's mind, the seemingly disparate elements of Illyria's article slotted laterally together into a shape that was both logical and sublime. Perhaps this was why he'd sensed Fred's presence in it all along; one had to think like her to understand it. Wes now realised that the entire paper was a single, elegant calculation. Energised, he started making sense of its sequences.

Trees. Trees and singing.

He blinked. No. This had to be solved in a specific way, and he couldn't do it alone. Rising and going to the telephone, Wesley lifted the receiver and punched a button. "Yes, Angel, it's me," he said. "I know what we have to do."

- - -

A vampire crept among the tombstones, as intangible as smoke. Most wouldn't know it was there, not until it was upon them. Spike had smelt it a mile off, reeking of death and its last feed – a leech's smell. Dirty bugger. Personal hygiene didn't cost much.

It approached a nearby mausoleum and reached for the door handle. Then it stopped and faced them. "Hi."

"Evening," Spike said.

The vamp looked the mausoleum up and down, shaking its head. "The rents in this town are criminal, just criminal."

"Tell me about it," Knox began jovially. "My old condo-" Illyria's gaze silenced him.

"Resume digging," she said.

The vampire smiled dryly, glancing from one to the other. "You're up and about late."

No doubt about that. Morning was in the air, in the first hints of moisture on every blade of grass. "No rest for the wicked, as they say."

"True," the vamp laughed. "See you at work, then."

"See you, Vic." Waving a hand, Spike watched Vic enter the mausoleum and close the door. He should really get a place with a shower.

Knox, meanwhile, was making a meal out of grave digging. He had it all wrong, lifting a clod here, another there. Sniffing the air, calculating exactly how long it was to sunrise, Spike began to suspect the man was stalling for time. Either that, or he'd never had a spade in his hand before. A bit of friendly advice, then. "Not like that. Dig a trench at one end and widen it. And use that shovel to clear out the spoil."

Turning, Knox held out the spade. His bonhomie had momentarily left the building. "You want to do it? Just so you know, we're digging down, not up."

Spike moved to snatch the spade from him, but was knocked out of the way as Illyria pushed both of them aside.

She exhaled impatiently. "I weary of this." Dropping to the ground, she attacked the grave with her hands, scooping out double armfuls of earth. Soon she was at the bottom of a sizable hole. Blue didn't bother digging through the last foot and a half; she just sank her arm into the ground and pulled a coffin out. Something inside it thumped against the lid as it was thrown from the grave. After climbing from the hole, she stabbed her fingers into the coffin's side and tore the lid off, spraying a few splinters around. Tentatively, Knox moved beside her and glanced into the box. Spike stood at her other side.

It had been months since Knox's death, and so he was a bit the worse for wear. Skin shrivelled and yellowed, teeth exposed and grinning, eyes gone. That was probably what looked nastiest to the other, upright, Knox. Robbing his own grave; that went a long way beyond irony. Poor bloke.

But Knox only hesitated an instant when Blue told him to get the sacraments, and was soon squatting and fumbling inside the shirt his cadaver wore. After a bit of cursing, he rose to his feet. He held half a dozen crystals, like the ones on Illyria's sarcophagus. Spike saw her eyes narrow in concentration. Her head cocked twice. A milky light in six different colours grew from the crystals in Knox's hand. It was a magical luminosity shinning there inside them, and yet it looked completely normal and a part of the world. With a shout, Knox dropped the sacraments.

Illyria lowered her eyes to where they lay and then raised her head to stare impassively at him.

"Sorry," he said. "I've never felt their power before." Then he gasped. "My king…" He laughed disbelievingly. "You're bleeding."

It was true. She'd yanked the coffin lid off so aggressively that a splinter of it was sticking into her cheek. Her hand brushed the splinter away. Holding the hand in front of her, she looked at the blood there. "Yes, Knoxy. If you prick us, do we not bleed?"

Faster than it was possible to see, her arm shot forward, fingers smashing into Knox's chest up to the knuckles. She was going to rip him in two. And her face – it had gone from frightening to bloody terrifying, gruesome. That answered a question, anyway. Illyria must be the only one pulling the levers at the moment. Fred would never be a party to this. Would she?

Before Spike could react, however, Blue had calmly removed her hand and now used it to point at the fallen crystals. "Pick them up."

A bleak, not shocked, expression on his face, Knox stooped and did as he was told.

"Now place them, Qwa'ha Xahn. Place them close to your heart."

Knox pushed the glowing crystals, one by one, into his chest. If this caused him any pain, he didn't show it; but he wasn't a happy boy, that much was certain. Maybe Angel was right, and the man was seeing his life's work and dream about to flush away. A shame, that.

Another fifty minutes until the sun. They were cutting it close, but there'd be time enough to get back to the car and its necro-tempered windows. They had the sacraments, they were on schedule, and Knox was still in one piece. So, two out of three. It was time to do this, time to hope.

I believe in fairies, Spike thought.