The main door to the apartment building opened, and a flurry of snow preceded a figure stepping inside. Harrison, the guard on duty, looked up, a smile creasing his dark face. "Mr Castle. It's good to see you again."

Rick smiled, shaking his shoulders to remove the dusting of snow on his overcoat. "Hi."

"Were you here to see Mr Canfield? Only he's not at home."

"No, not business this time." Rick approached the desk, aware of the security cameras on the walls above him, covering every inch of the lobby. "This time it's purely pleasure. I was just impressed with the building," he said, leaning his elbow on the raised edge at the front of the desk. "I've been looking for somewhere else to live ... you know how it is, you get bored stuck in the same rooms after a while, and you need some place new, some place different. And I was wondering whether there were any vacancies here."

Harrison nodded slowly. "There's a couple. Not many people can afford the kind of rates that get charged, not in times like these, so there are two apartments I'm aware of, and Mrs Brannigan is talking about moving out to the Hamptons, to be closer to her sister. She's got Alzheimers."

"That's sad. I can't even imagine what I'd do if I began to lose my faculties."

"Me neither, but as a writer it would be worse for you. Not being able to imagine things."

"Exactly." Rick smiled and leaned over, patting the man on the arm. "Exactly, my friend."

"I can't let you up to see them, of course," Harrison went on. "The empty apartments, I mean. Not without the agent accompanying you."

"No, of course. And I wouldn't want to get you into any kind of trouble." He looked so open and honest, even the most sceptical of souls would have believed him.

"I can give you the name and telephone number, if you like."

"That would be good. But there are a couple of things you can answer for me, though."

"If I can."

Rick tapped the book in front of the guard. "You log everyone in?"

"Every single person, in and out," Harrison agreed. "Visitor, tenant, workman ... they all come through me and I write them down."

"You don't have it computerised?"

"No. That's the owner's choice, too. When I took the job I told them I could handle anything electronic, but they said that was too easy to alter. Hard copy, that's what they told me." He showed Rick, lifting the page. "See? It's carbonised, so there's always a duplicate. If I make a mistake, I can't just rub it out."

"But you don't make mistakes, do you?"

"No, sir, I don't. In my line of work, you can't afford to."

"Which is good for me," Rick said, explaining, "My mother lives with me. She's a dear, but almost an invalid, and I have to be out a lot, so I need to know she'd be safe." He sounded so sincere even he could almost see her, sitting in her wheelchair, martini in one hand, a silver fox by the collar in the other ...

"That's nice. That you look after your ma, that is. Too many folks nowadays don't know how to take care of the people who brought them into this world."

"Isn't that the case." He lowered his voice. "But then, I'm also a red-blooded male, and I do occasionally have ... ladies visit." He didn't quite wink. "And being something of a celebrity, there are some things I really don't want the press to find out." What, he couldn't quite imagine, although he was sure there were some dark things in his past that he didn't want the bright light of day shone on. If he was given a week or so to think about it.

"I don't understand."

Rick sighed inwardly. "There might be visitors I don't want noted. Or seen." He glanced up at the camera above the desk.

"Oh. Those kind."

"Yes. Those kind." At least he hadn't had to spell it out, although it was a close run thing.

Harrison looked contrite. "Well, if they come through the front, then they go in the book."

"Through the front. So there's another way in?"

"No, now, I didn't say that."

"Of course not." Rick paused. "So how are you liking my latest book?"

Harrison was confused by the apparent change of direction. "It's good. Great, so far. I'm about half way through."

"You know, I'm writing a new one. First in a series. A female main character."

"Nikki Heat." Harrison leaned forward. "I saw it on your website."

Rick had to grin. "I knew you were a fan."

"Always have been. I've got all your books. Storm Fall is the only one I've got signed, though." He chuckled. "I was going to go to one of your signings once, but I had to work, and by the time I got off, the store was closed."

"That wasn't fair."

"That's life."

"I suppose." Rick made like he was pondering something, then said, "You know, I have a spare set of first editions at my home. And if I do move, well, I might have to find somewhere else for them to live. Somewhere I'd know they'd be well-looked after. Particularly if they were individually signed to the person who was doing the looking after." He watched as the penny dropped.

"You'd do that?"

"I would. Besides, I'm always looking for characters for my novels. And this building is so unique, I wouldn't be surprised if it turned up in one. Along with its day guard."

It was too much. Harrison made sure nobody was listening, which wasn't difficult since the lobby was empty apart from them, and then said quietly, "There is another way in. It's meant to be a secret, but if the tenants ask, I have to tell them. And you're thinking of becoming one, so I suppose it won't harm that much."

"Of course it won't." Rick smiled. "So where is it?"

---

Kate was beginning to see double. Every time she looked at one of the employee files, the face would stare back and laugh at her. Or so it seemed. And then having to check them through the database ... she'd been right when she told Montgomery it was going to take a long time to account for them all, and there was still this prickling feeling at the back of her neck that something wasn't right.

Maybe it was because her shadow wasn't there. Wherever he'd gone, Castle still hadn't returned, and it was beginning to bug her. Not that she wanted him around, and it was worse if she was starting to feel odd when he wasn't, but ... there was always a 'but'. But she wanted to know where he was. But he made her think twice about some things she'd always taken for granted. But he could bring a fresh eye to the evidence, and suggest something so outrageous that it might just be true. And then make her feel like maybe it had been her idea in the first place.

He was wrong in this case, though. Canfield wasn't their man. He couldn't be. The only evidence against him was circumstantial, and what with the unshakeable alibi he had ... There it was, that prickling again.

She tossed the latest file on the finished stack and looked across at Esposito. "Anything?" she asked.

"Nada." He leaned back and stretched. "You?"

"Not a thing." She dropped her head between her shoulders, trying to rotate the ache out of them. "We'll get there."

He was impressed by her determination. "You think Ryan's doing any better?" His colleague was looking through hours of footage from various surveillance cameras, traffic cameras, any kind of camera that might give them an inkling as to what happened.

"I'm sure we'd hear if he had." Her phone rang, and she picked it up. "Beckett."

"It's Maggie Maguire." There was traffic noise in the background, and she sounded like she was slightly out of breath.

"Miss Maguire." Kate tried not to let any resentment show in her voice. "What can I do for you?"

"You can stop Rick doing something incredibly stupid."

"And what would that be?"

"Breaking into Merrick Canfield's apartment."

"What?"

"He's at Canfield's building, and he says he's going in to look around."

Kate closed her eyes. "Is he insane?"

"I don't know. I think, maybe a little. He's convinced Canfield is involved, and since you won't believe him, he –"

"It's not that I don't believe him," Kate interrupted, and realised, perhaps for the first time, that she just might. "We don't have the evidence."

"Well, he's not taking that as an answer." The traffic note changed, as if she'd entered a building. "He said something about the article being torn, not cut. Does that mean anything to you?"

"What art ... wait a minute." When Canfield had gone, she'd realised he'd left the New York Times article on Amanda Tyler in the interview room, and she'd picked it up, put it somewhere. "Hang on." She lifted up the files in her tray, finally snagging the one she wanted. Opening it, she saw the article, lying on top. Torn, as Rick had apparently noticed, not cut.

"Do you have it?" Maggie was asking.

"Yes. Just ..." She was seeing Canfield's apartment in her mind's eye, everything in its place, not a scrap of anything lying around. And she'd seen the look on Canfield's face when Rick had deliberately spilled coffee into the tray. "I'll call him. Make him leave, before he gets into too much trouble."

"Too much trouble? If he's right, he might get hurt, possibly even die!" Maggie was getting more and more upset. "And I don't want that. And I don't really think you want that to happen either."

"Miss Maguire -"

"Boss!" It was Ryan, sticking his head through the open door. "You need to see this."

She nodded, holding up one finger. Give me a minute, she was saying, even as she spoke into the phone again. "Miss Maguire ... Maggie ... thanks for telling me. Now go home and let me deal with this."

"No, I –"

Kate hung up and looked at Esposito. "Chase Canfield's history. Castle was right. The man we met at the apartment wouldn't have torn the article out. Something is very wrong. And try and get him on the phone."

"Who, Canfield?"

"No, Castle."

"You got it, boss."

She followed Ryan around to one of the other offices. "So what am I looking at?" she asked, peering at the screen in front of one of their techs. The image was of a street, something like a plaza, somewhere she thought she should know.

"CCTV footage from outside the Lincoln Centre the day Canfield said his bass was stolen. We don't get a perfect view, but …watch."

People passed to and fro, then a man appeared in the corner, hailing a cab.

"What the …" Kate leaned forward. "Back it up." The tech did as he was told. "Now slowly forward. And can you zoom in?"

"Some. The picture gets too grainy the closer I get, but …" He manipulated a roller ball. "How's that?"

The image enlarged, juddered enough to make the watchers feel a little seasick, then steadied.

"Perfect." Kate studied the picture. "Well, well. Merrick Canfield."

Ryan checked his notes. "In his statement he said he never left the building. Just went for something to eat, and when he came back the bass was gone. But that's not everything," he added, tapping the tech on the shoulder. "Brian, forward it."

Brian nodded, and the image zoomed out a little again, and the time clock in the corner of the screen began running forwards. A cab pulled up, and Merrick Canfield opened the door, about to get in.

"Hold it," Ryan ordered. He looked up at Kate. "See it?"

"See what?" Maggie asked from the doorway, her face flushed from running from the elevator. Apparently the building she'd entered was the precinct house.

"You shouldn't be in here," Brian, the tech, said, pointing to the sign. "It's off limits to -"

Maggie interrupted him. "What? What do you see?"

Kate straightened up slowly. "Merrick Canfield. Getting into a cab. With what looks suspiciously like a double bass case."

"The one he said was stolen," Ryan added.

Esposito ran in, pushing past Maggie. "Boss, you are not going to believe this. I just got the information on Canfield's background. He was a twin."

Kate stared at him. "What?"

"His brother was kidnapped, aged two. The parents paid the ransom, but the kid was never returned. Everyone assumed something had gone wrong, the boy was killed, and he was declared dead seven years later."

"More twins," Kate muttered.

"Oh, it gets better. The dead twin's name was Andrew."

"He's not dead," Maggie said, stepping forward. "It's the only thing that makes any sense. If Andrew is still alive, somehow he found Merrick ... and they've been playing everyone for fools."

"And Castle's walking right into the middle of it all." Kate hurried to her desk. "Call for a warrant. This should be enough if Judge Markoway isn't feeling too pedantic, then get someone to bring it to Canfield's building." She saw Ryan pick up the phone but was already taking her gun from the drawer and sliding it into its holster. "Did you get hold of Castle?"

Esposito shook his head even as he was shrugging into his jacket. "Only some kind of crazy recorded message."

"That was him," Maggie said tensely, her arms wrapped around herself. "He did it to me."

"Well he didn't answer when I spoke," Esposito said.

Kate grabbed her coat. "We'll try again on the way."

Maggie stepped forward. "I'm coming with you."

"Oh, no, you're not. You're a civilian. I can't let you –"

"Rick's a civilian! And he goes with you all the time!"

"He signed a waver. Besides, if ..." Kate stopped, picking up on the absolute and honest distress of the other woman. "Maggie, go home. Stay with Martha and Alexis. As soon as we know anything, I'll call. I promise."

"Warrant's on its way," Ryan called.

Kate put her hand on Maggie's arm. "Please. I can't be worrying about you too."

There was a tight silence for a moment, then Maggie nodded. "Call."

"I will." Kate nodded just once, the understanding between them clear as crystal, then ran out of the squad room.

---

Harrison had been right. The entrance to the back stairs, in the corner of the underground car park, looked like just the maintenance doorway it was posted up as. It was locked, of course, but that wasn't too much of a problem. Odd, that with all that security at the front, the builders only used a simple tumbler lock at the back. Even a child could get in. Well, a child with a set of professional lock picks. Rick smiled as he rolled the black velvet up and slid it back into his pocket, and mentally thanked the man who'd taught him several years ago.

"Now, Ricky, don't you go doing anything you shouldn't with it," Norman, aka 'Barney' Rubble had said. "I'm showing you this in good faith, just because I like you."

"And because I'm paying you."

"That too."

"It's research, Barney. If I don't get Derrick Storm out of the locked room, it's going to be a short book."

"Yeah, well. Just don't get caught being illegal."

He never had. Well, maybe borderline illegal, but nothing like he was doing now. And as far as he was concerned, this was justified. Checking the car park once more, Rick slid through the door and started up the stairs.

Damn, but he needed to take more exercise, he considered, as he puffed his way past the fifth floor. Playing all those games with Alexis apparently wasn't enough, nor was chasing Kate all over the city. Perhaps he should actually use the family gym membership he paid out for every month, instead of just hoping it worked like osmosis. The only times he'd been in there was during the first week, when he'd pulled something on the rowing machine. She was twenty-eight, brunette, and apparently wanting to get into acting.

He grinned, remembering that hot, tempestuous, passionate July weekend, and wondered if the hotel they'd stayed at had forgiven the broken nightstand yet.

Here it was. The penthouse. The little roll of picks did their work again, and he stepped through into Merrick Canfield's apartment.

It took a moment for him to orient himself, but then he realised he was in the kitchen area, looking towards the huge windows and the view of a snowy Manhattan. He listened for a moment, trying to gauge if anyone was around, but all he could hear was his own heartbeat slowly returning to normal and the slight hum of the heating system. And his phone ringing.

Tugging it from his pocket he glared at it, then pressed the button. "This is Richard Castle. I'm sorry, but I'm not available right now. But if you'd like to leave your name, number and vital statistics, I'll get back to you." He paused, then whistled a single, high tone.

"Castle? Damn it, Castle, are you there?" It was Esposito. "Look, if you are, don't do anything. We're coming to you. Just stay away from Canfield, okay? Castle? Shit." The phone went dead.

Rick had to smile. Maggie must have persuaded Kate he was right. The smile faded a little. Except Kate was going to be mad, and she would probably take that out on him by arresting him. And he could only rely on so many 'get out of jail free' cards from the Mayor. Better be looking around for the proof he needed.

Thumbing the phone to silent vibrate – something he had managed to figure out – Rick thrust it back into his pocket as he paced through the main living area, but once again nothing was out of place. There was no conveniently lipstick-stained cup in the sink, or illicit item of ladies lingerie peeking from under a cushion. He even scraped through the ashes of the fire, sending a faint smell of pine into the air, but there was no trace of anything untoward.

He took a deep breath and looked around. Ah. The master bedroom. That was a distinct possibility.

Standing just inside the door he let his eyes roam the room. Lots of brown leather, framed pictures ... in fact it was a lot like his own, and he made another mental note to redecorate. At least his didn't look like it had been created in one fell swoop, each individual item put in place because the designer decided, not because it was wanted or needed. No photos, either, not of family or friends. Tidy, of course. Exceptionally so. A place for everything and everything in its place. Totally what he'd expected.

Except for the large aquarium against the far wall. Small fish, some with big eyes and an almost human expression on their faces, swam silently backwards and forwards through the reeds, darting through the empty portholes of the sunken galleon in the corner, endlessly moving from left to right and back again.

Rick stared at them, almost hypnotised as he moved closer. He had no idea what puffer fish looked like, but he'd bet the entire proceeds from his next book those little bastards swimming around in the water were exactly that.

"See, Kate," he murmured. "Told you so."

Quelling the impulse to call her and gloat, he instead took a couple of photos with his cellphone, the flash making one of the small fish expand until he thought it was going to explode.

He grinned, making sure that one was in the frame of the last shot. "Gotcha."

An open doorway beckoned, and he walked through into the ensuite bathroom. Pulling the light cord, he wasn't surprised to see it spotless, but this time his interest lay in the cabinet over the sink. Shaving cream, a cut-throat razor – perhaps being a musician meant having a steady hand – next to an antiseptic wand. Okay, maybe not that steady. A box of condoms ... maybe he got lucky occasionally. And a bottle of pills.

Rick lifted them out, reading the label. 'Nitrados', it said, prescribed by an upmarket doctor and filled at a local pharmacy. 'One to be taken at night when required. Warning – do not take with alcohol. In case of overdose call 911.' He turned it a little, reading the active ingredient. Benzodiazipine.

He shook it, then checked inside. Almost empty, and the scrip had only been written two weeks before.

For a long moment Rick just stared at the plastic container. Here it was, everything Kate needed to go after Canfield, and yet none of it was hidden. It was as if the man knew the police didn't have the evidence for a search warrant, so he hadn't bothered to dispose of it. That spoke of a blinkered, controlled mind.

Once again he took a photo, just in case, then shuddered as something walked over his grave. Putting the bottle back, he closed the door, catching sight of his own reflection, his expression grim. He needed now to get outside into the fresh, cold air, to let it blow away the taste of death from his throat.

Turning off the light he glanced at the aquarium again, something niggling at him. One of the fish swam to the bottom, causing some of the sand to swirl up into a vortex before settling back again.

"It can't be that easy," Rick muttered. "It's a cliché ..."

He crossed to the fish tank, looking for and finding a small net hooked onto the side, probably for scooping out detritus and dead fish.

For a moment he could see, playing in his mind, Alexis, aged five, desperate for one of the goldfish at the carnival, and him spending more money than it was worth to win it for her. It hadn't survived beyond a week, and Alexis had cried for hours when it died, but they'd buried it in the park when no-one was looking, as he read a specially composed piece, and his daughter had taken flowers to the site for a long time after.

No. That was a memory for a better day, when he wasn't trying to catch a murderer.

Using the little net, he pushed around in the sand, then it caught, dragged. He lifted it out, the water running off something. Something the size of a quail's egg. More specifically, a diamond the size of a quail's egg.

"No imagination," he whispered to the fish, pulling the net back up and taking the gem from inside. Gaudy and vulgar ... yes. But also proof positive. He went to pick up the cellphone he'd put down next to the tank.

"Mr Castle."

Rick froze, the diamond in his hand dripping water back into the aquarium.

"That isn't yours."