Chapter 1

Poliad, Beckett knew, wasn't actually a word from Ancient Greek, but she didn't have a better one. After all, there were naiads, dryads, and oreads. Why shouldn't there be poliads? Okay, it was a bastardised word, but what else could you call the spirits belonging to cities?

Anyway. Whatever you called it, she was one. Part of the fabric of New York. She had to admit, it was pretty helpful. She could fade back into the walls of the buildings, or sink into the subway system. She could hear the rhythm of Manhattan, pulsing in time with her heartbeat. Yes, she had a heart, and blood pumping around her body. It was just a little more, um, flexible than humans were, which was generally helpful as a cop. A number of bullets, knives, punches and so on had been dodged with the assistance of inhuman reflexes and sinking just a fraction into walls.

A number of cases had been assisted (or something like that) by listening to the city's whispers. All totally provable in court, of course: there wouldn't be any point in not having a solid case for the DA, but knowing where to look speeded up matters amazingly.

Everything had been just fine. For detectives, Ryan and Esposito were remarkably blind to any indications that she might be faster or stronger than perhaps she should be; and took her deductive abilities at face value, never suspecting her enhancements. It was probably best that they didn't. Quite how she could explain that she was…what she was…No. Anyway, even Ryan, the closest thing to a leprechaun that the totally human race could produce, wouldn't believe in poliads. (Should it be polisads? Nope. That sounded too much like palisades, and she wasn't a yard fence.)

They'd done just fine for years. Nobody had looked too closely, because everybody, especially Captain Montgomery, just loved their solve stats. Oh yes. Since everything stacked up, every procedural i dotted and t crossed, everything squeaky clean and shining white, with perfect accuracy…nobody ever asked a thing. Nobody looked over their – her – shoulder.

Right up till they got saddled with Richard-asshole-Castle, who wanted to observe. And did. Closely. Very closely, though he'd like to observe more closely still, right down to the surface of her skin, and beneath. She couldn't get rid of him. He stayed as close as a rash, though his company was less desirable than the nastiest, itchiest rash in medical history. (So she told herself, and ignored the answering heat deep in her body.)

Not only was he infuriatingly close all the goddamned time, not only did he ask endless questions, but he thought he knew about the city. And he showed off his knowledge all the time and expected her to be impressed.

She wasn't. She knew more about the city by waving her little finger or just shutting up and listening, which he never ever did, than he would in a million years. At least a million years. No matter what she did or said, he smiled that infuriating smirk and kept on following her and observing.

And talking, and talking and talking. Couldn't the man ever be quiet? Even a few moments of peace would have been welcome. He was worse than the legendary, definitely mythical Dionysus in the middle of an orgy. (And no, she wouldn't want an orgy with him. Definitely not.)

And she couldn't get rid of him. Orders. Montgomery had put his Captain's foot down and told her straight, "He stays, Beckett. No more arguing." So she had to put up with him.

So, on a wet Wednesday in April, here he was in her unit, talking. Babbling nonsense, as usual. She wasn't listening, as usual. Until –

"So I don't get how that guy missed you. I mean, sure you dodged fast but I calculated the angles and no way should he have missed."

Oh, shit. She'd faded into the wall just slightly: enough for the punch to go wide. "So you're a math genius? I guess it makes up for your writing."

"Ouch. Especially as I know you've read all my books." He smiled sweetly. "But yes, I got an A in math."

"Then it's worn off. He missed me. So your calculations were all wrong." She bared teeth. "I guess you're not a math genius either."

Castle regarded her balefully, but subsided into silence, which Beckett regarded as a major win, all the way to the crime scene.

At the scene: a grimy alley in a dubious area of town, Castle had, just for once, remained quiet. Beckett listened to the whispers of the sidewalk outside the alley, and the emanations of the bricks in the walls, by the simple method of standing on the sidewalk (shoes were no barrier) and leaning casually on the wall. Touch was touch, and she only needed a little of it for everything to become plain.

"Any cameras?" she asked, prodding at the greasy ground.

"Yeah, but the angle's not great."

"Pull the footage anyway." She considered, though she already knew. "Lanie said time of death was between six and ten, yeah?"

"Yo."

"Okay, that's our window." She prodded the ground again. "There's a footprint here." There was now. "Let's get photos, and if there's a footprint, let's see if our killer was dumb enough to lean on the wall here." He had been. "There might be fibres or even a partial print."

"How do you know?" Castle asked from behind her.

She jumped. "How do I know what?"

"That he stood there."

"Footprint," she snapped. "See it?"

"But he might just have walked. How do you know he stood there?"

"I don't. And I didn't say he did." She hadn't. She had been extremely careful with her wording, as she always was. "I said if there was a footprint, he might have leaned on the wall. That's hardly a statement of fact. It's a possibility. CSU'll tell us if it's likely."

"But that footprint wasn't there five minutes ago."

"Do you need an eye test? Of course it was. Footprints don't just appear from nowhere. You missed it."

"I'm a trained observer!" Castle said indignantly. "I don't miss things. It wasn't there."

"You must be smoking illegal substances. It was there. You can see it. Footprints don't appear out of nowhere."

Castle griped and grumbled and groused, all of which Beckett completely ignored. When CSU found some fibres and a print, she smirked. "Told you so."

"That footprint wasn't there," Castle muttered.

Beckett ignored him. The memory of the footprint had been there, all she'd needed to do was recall it to the sidewalk's surface. It wasn't like she'd invented it – that would be wholly wrong, and she would never falsify evidence. She was merely recovering it, as a good cop should. A slightly way-out version of CSU, really.

Castle remained quiet all the way back to the precinct, where, annoyingly, he followed Beckett to her desk and perched in a chair that he'd found somewhere. "It wasn't there," he insisted. "I was looking right at that patch, and there weren't any marks at all."

"Then I suggest you go get your eyes tested, instead of annoying me," Beckett snarked. Castle harrumphed. "Anyway, nothing more is going to happen till CSU tell me if they found anything. Ryan," she called, "you got that request for street cam footage in yet?"

"Yes, Beckett," Ryan said patiently. "I did it as soon as we got back."

"Okay. Lanie's got the body, CSU have the scene, so Espo, what did the run on our vic show?"

Esposito slouched over. "Darren Calver. A few misdemeanours – disorderly conduct, that sort of thing." He paused. "And five years for home invasion. No weapon, disturbed before he took or damaged anything."

"I see. When'd he get out?"

"Three weeks ago."

"He sure got into trouble quick," Ryan said.

"Yeah. Wonder what he was up to?"

"Maybe his mom would know," Espo suggested. "She's next of kin."

"Mm. Ryan, you try and find some friends in his phone. I'll go talk to his mom." She stood up, followed instantly by Castle.

"Field trip," he said happily.

Beckett favoured him with a glare. "Informing next of kin isn't a jaunt," she chided. "Telling his mother that her son is dead isn't a cheerful conversation. She deserves some respect."

Castle subsided. Sadly, he wasn't squashed for long, and as soon as they were in her unit and travelling to Calver's mother's home, in New Jersey, he began to chatter again. "Maybe the victim swindled his killer out of the proceeds of the home invasion," he theorised. "The killer wanted to know where he'd hidden them and killed him before – no, once – he found out. He's in a grimy, dark warehouse right now recovering his loot."

"I don't think so," Beckett said, based wholly on the whispers of the sidewalk and the wall on which her perp had leant. He'd gone skiting off as soon as he'd realised he'd hit too hard. Later, she'd go back, and trace his path. After Castle was well out of the way. Once she'd done that, she'd get street cam footage based on the direction he'd taken. Everything had to be evidenced…but no harm in using her talents to direct the search for evidence where it would do most good.

Calver's mother proved to be a hard-faced bottle blonde of around fifty, who regarded them with weary contempt. "What's he done?" she said, before Beckett could open her mouth. "'Cause I ain't bailing him out again."

"Mrs Calver, I'm sorry to tell you that Darren was found dead earlier this morning."

"Dead?" she shuddered, face grey. "How?"

"He was murdered."

"Murdered?" She staggered, catching herself on the doorpost.

"May we come in?"

"Yes…." She reeled inside, to a small family room, half-falling on to a shabby sofa. "Dead? I don't…why?"

"We were hoping you could help with that," Beckett said. "Can you tell us where he was living?"

"Once he got out, you mean?" his mother said bitterly. "Here. When he bothered to come home at all."

"Where did he go?"

"Hanging out with his no-good friends in the city. They got him into trouble."

"Mmm," Beckett hummed, which certainly wasn't agreement but could be taken as such. "Who?"

Mrs Calver provided four names and her best guess at their addresses, which was fairly poor. Still, Beckett would be able to find them, one way or another.

"Is there anything else you can tell me?" she asked.

"No. I can't think of anything more. He'd promised me he'd go straight…" Finally, tears gathered in her eyes.

"I'm sorry," Beckett said. "If you do think of anything, call me."

Mrs Calver showed them out.

"Now what?" Castle asked.

"Back to the precinct to try to follow up these friends. I have enough here to be able to start."

"Oooh, investigations," Castle bounced. "I can help."

"How?" Beckett inquired tartly as she pulled away from the kerb.

"Fuzzy logic," he offered up.

"Fuzzy, I'll give you. All your theories are fuzzy. Logic – that'll be a first. You're never logical. Fuzzy or otherwise. The only thing that's fuzzier than your thinking is a Malamute puppy, which has the huge advantage over you of being cute and lovable."

"Very mean," Castle said lazily. "Fuzzy logic means looking at the shades of grey rather than strict black or white."

"I'm perfectly well aware of what fuzzy logic means. If I want definitions, I'll look up Websters. That still doesn't explain why you think you can help." Her tone suggested that she didn't think it was possible, which was exactly what she intended. Her irritating shadow was even more irritating when she wanted him gone for the day. Her investigation wasn't going to finish with the databases and an address book. Now that she had names, another dive into the undercurrents of the city would provide her with a shadowy vision of the owners of those names.

If, that was, she could only have some peace and quiet. Castle chattered all the way back to the precinct, until she was tempted to push him out of the car.

"Will you just shut up!" she snapped. "I can't think with you blathering" –

"Ooohhhh, lovely word!"

"Be quiet! I want to think and you're getting in my way."

"Is there a problem here, Detective Beckett?" Montgomery oozed up behind her.

"I'm trying to investigate a murder, sir. Castle is trying to distract me."

"I'm not trying," Castle said indignantly. "I'm succeeding."

"That isn't the winning argument you think it is," Beckett snipped.

"You're deliberately stopping my detective solving murders?" Montgomery asked. "I don't think that was the deal I made with you." An edge of irritation had crept into his tone.

"I'm not stopping her. I'm trying to point out some alternative addresses that she might try searching."

"You are not," Beckett argued.

"I am. Look." He passed a sheet of paper across the desk, on which were scribbled eight to ten street names.

"Why couldn't you have done it quietly?"

"It seems that Castle's been helping, Beckett. I think you owe him an apology."

She stared incredulously at her captain. "I what?"

"Apologise, Beckett."

"I'm sorry if you were upset."

Castle's face said that was more than he'd expected. Montgomery's pinched lips said that was considerably less than a fulsome effort. Beckett's face said that's all you're getting, swiftly followed by get the hell out of here before I shoot you both. Montgomery slid off, his spine radiating smugness.

Castle grinned widely, but, as she reached threateningly towards her hip, bounced out of his chair, calling, "Till tomorrow, Beckett," as he hurried to the elevator, still grinning in an offensively overpowering manner. She wanted to shoot him, but that would be unprofessional. However…

Castle tripped, and only just caught himself. He looked confusedly at the floor. "It moved!" he said.

"Don't be dumb. Floors don't move." They didn't. But the linoleum did. Just a little. It was petty and mean – and served that irritating so-and-so right. She didn't feel one bit guilty. If he'd actually fallen over, she might have, but since she'd noticed that however klutzy he pretended to be, he never hurt himself or suffered any damage, she'd taken the chance. She felt better already.

Castle reached the elevator without any more incidents, betook himself home, and then gave himself up to think furiously. He was sure there hadn't been a footprint – oh. Oh, oh, ooohhhhhh. He'd taken a couple of snaps. That would prove it hadn't been there. And then he would have a talk with Beckett. Oh, yes, they would talk.

He flicked through the photos on his phone, all neatly timestamped (a holdover from his million or so pictures of Alexis) and regarded them closely, in chronological order. There was the sidewalk – and no – he punched the air – there had been no footprint. Five minutes later – there was a footprint.

That was…weird. Utterly crazy. Footprints didn't just appear from nowhere. At least, they didn't if you were a human cop. And how exactly had Beckett known it would be there when it wasn't there?

Clearly, Beckett had a secret. Kate Beckett, realist extraordinaire, sceptic, cynic, and puncturer of all known forms of supernatural speculation, had a supernatural secret of her own.

And he, Richard Castle, Master of the Macabre, was going to discover it. Because he had one talent that Beckett certainly did not know about.

Beckett announced to the bullpen that, since there was nothing more to be gained that evening, she was leaving. It being a mere two hours or so after the end of her shift, that caused nobody any surprises. She swung out, and without delay arrived at the scene of her murder. She let herself slip into the currents beneath the physical surfaces of sidewalk, walls, and kerbstones; listening to the whispers beneath the sounds of vehicles and horns; chatter and bustle; the rattle of the subway below. Gradually, the picture became clearer – faded from earlier, but still good enough. She began to walk, following the trail of her murderer, keeping a note of the route so that she could request footage from cameras along the way.

Unsurprisingly, the trail led down into the subway. That…wasn't a problem. Beckett carried right on, listening to the rails zing as she stood in the station; absorbing the atmosphere through the tiled walls, gently, imperceptibly, fading into the surface until she had entirely disappeared. In Manhattan, nobody would notice. Nobody noticed anything in subway stations, as long as there wasn't noise and fuss.

The walls, a little wistfulness in their tone as they realised she wouldn't stay for long, told her incorporeal form that her suspect had taken the uptown train at around ten that morning. It was enough, for now. She reassembled herself, and made for home, where there would be pizza, a glass of wine, and a nice hot, bubbly bath. (And no, absolutely no, irritating shadows with blue eyes, broad chests, and considerable heat in their appreciative gazes.)

All three items arrived without a hitch, and, beautifully refreshed, Beckett settled herself on her couch to read and watch easy TV shows, for which no brain or concentration would be required. She snuggled into her heavy, silky robe; wiggled her toes happily in their warm slippers; and let the world wash over her, soothed by the gentle susurrations of the city around her apartment. The lullaby of Broadway wasn't just a song from an old musical. For Kate Beckett, it was the background to her life, there as long as she could remember. Tonight, as for the last few nights, the city was soft and somehow plaintive, drifting around her as if seeking something.

Her comfortable reverie was rudely interrupted by a banging on the door. She peeped through the spyhole, and realised that it was only Castle, whom she did not at all want to see. Bad enough that he plagued her all day; she didn't want him plaguing her off-duty as well – and how had he known her address? She certainly hadn't given him it. She thought hopefully of not opening the door, and then thought that he would surely call her phone, which would prove her to be there and hiding from him.

"What?" she said coldly.

"I can prove there wasn't a footprint there!" Castle said, pushing in past her. "I had photos."

"Photos?" Oh shit oh shit oh shit. How was she going to get out of this one? What was he doing taking photos anyway?

"Yes, photos. And they show that there wasn't a footprint there one minute, and the next minute there was." He scowled. "They're time-stamped."

"How odd," Beckett said. "Are you sure they're time-stamped correctly? Footprints can fade."

"Yes, I'm sure." He regarded her carefully. "How did you do it?"

Beckett had been waiting for that since she'd looked through the peephole. "Do what?" she said calmly.

"Make the footprint appear."

"People can't make footprints appear," she pointed out. "That's ridiculous."

"It would be, except that you also evaded that punch when there was no way you could have done that short of merging with the wall."

"That really is ridiculous," Beckett snapped. "You've been sniffing something. Or brewing up herbs. Or maybe smoking funny cigarettes. People don't merge into walls, footprints don't appear out of nowhere and the most likely explanation is that you've gone crazy."

Castle snapped his fingers, and the world changed.

Thank you to all readers and reviewers.

My entry for the Hallowe'en Bash, on the basis that it's vaguely supernatural. Chapters 4 and 5 (of 5) will be M-rated. Usual schedule: Thu/Sun/Tue.

It wouldn't be me if I didn't remind you of my original books: the Casey & Carval series: available from Amazon. Search SR Garrae.