Rick was bored. They might have a dead body, but with no identification, no idea of cause of death and no suspects, there was very little he could do. Apart from annoy Kate, of course.

But even that wasn't happening. Kate was taking the opportunity to catch up on some paperwork while waiting for Ryan to come up with something from his trawl through the missing persons files, while Esposito was completing his neighbourhood canvas. She was effectively ignoring him, no matter what he said or did.

In fact, Rick was so bored he was on the verge of going home and annoying Maggie instead, except one glance at the clock told him she'd be at her meeting right now, probably telling whoever would listen exactly what she thought of them. Tiredness, plus irritation and Maggie's occasional natural pig-headedness was not a combination to be taken lightly. And being accused of plagiarism wasn't going to improve matters.

Plagiarism. Honestly. What kind of idiot would accuse Maggie of that? Her novels were so carefully worked out, so meticulous in their research ... of course they were original. Oh, there'd be the odd details that might be similar to something someone else somewhere had written, but it was pretty much in the realms of a hundred monkeys on a hundred typewriters eventually writing Hamlet, or something like that. There were only a finite number of stories in the world, and in the realm of crime there were bound to be similarities here and there.

For one thing there were only a certain number of ways to kill someone – shooting, stabbing, poison, suffocation, maybe a couple more, and a limited pool of suspects – husband, wife, lover, child, business partner, fan, even someone totally unknown to the victim. No, the skill came in the combination of who, what, when, where, how and why. And although Maggie may have been inspired, even influenced by other writers, she'd never steal. So it all had to be about money. Filthy lucre. Thirty pieces of ...

Kate's voice brought him back.

"You're very quiet."

He looked at her, but she was still studying the file in front of her. "Am I?"

"Yes."

"Is that so unusual?"

"Pretty much. I'll have to make a note of it in my diary."

He sat up. "You keep a diary? Can I read it?"

She threw him a glare. "No."

"To the keeping or the reading?"

"Either. Both."

He scrutinised her closely, his eyes narrowed. "Nope. I don't think you do. Not now. But I bet you did when you were young."

"Really." She sat back, tapping her pen on her bottom lip.

"Mmn." He smiled. "Alexis does."

"Has she let you read hers?"

"Yes."

"Really."

It was the tone in the second 'really' that somehow had him ... thinking. "What?"

"Oh, nothing."

"No. It's not. It's definitely something. What?"

"She let you read her diary."

"Yes."

"I imagine it was pretty vanilla."

"Snow's darker," he agreed, obviously proud that his occasional tendency to ride naked through Central Park hadn't been passed to his daughter.

Kate nodded. "Of course." Her lips twitched.

Now Rick was concerned. "What? Kate –"

"A ringer."

"What?"

"You say 'what' once more and I'll begin to think you're going deaf."

"Kate ..."

She took pity on him, a little. "She's got two diaries. She lets you read the one that's ... ordinary. Talks about the films she's seen, her school work." She could see his mind working, could almost hear the thoughts in his head. "Then there's the other one." She had to stop the lip twitch becoming a grin at his expression.

"You mean ... are you saying ..." He couldn't finish, closing his jaw with an audible snap of his teeth.

"It hadn't occurred to you that she just might be as sneaky as you are?"

"No."

For once Rick didn't pick up on the suggestion he was sneaky, and Kate felt a prick of guilt. Instead he looked worried, imaging all sorts of things that a pretty, vivacious sixteen year old could get up to.

Okay. Maybe this was just a little bit too cruel. "Castle, I'm sure she doesn't have anything bad to write anyway."

"Right."

"She's Alexis. She's the sensible one."

He took a breath. "True. But she's intelligent, too. It wouldn't take much for her to be able to ..." He swallowed. "Was yours ..."

For just a split second she wondered whether to tell him the truth, but instead went with, "No, Castle. Mine was pretty much wishful thinking."

She could see him relax, just a notch.

"So it was all about whoever you were crushing on?"

"Mmn."

"And who was that?"

"Nobody I intend to tell you about."

"Teacher, student or film star?"

"Castle ..."

"Come on, for Nikki Heat."

He was back to normal, and she tried not to shake her head. He was so easy to distract sometimes.

"Even for Nikki Heat. Use that supposed huge imagination of yours."

"Not the only thing that's huge," he joked, then quickly went on before she could comment, "Besides, I might be wrong."

"You? Never."

"Are you being facetious?"

"Me?" She glanced down at the heap of files still waiting on her desk to be reviewed and initialled, and felt an urge to be sidetracked herself. "So, did you and Alexis have a good time?" she asked.

"At the Guggenheim?"

"Yes."

"Of course. I always have a good time with my daughter. I'm a good time kind of guy." He waggled his eyebrows at her, and the urge to be distracted vanished like the morning mist.

She sighed, but luckily the words that were about to cut the author down to size were put on the back burner as the phone went. She picked it up. "Beckett." There was a pause, then she said, "We'll be right there." Hanging up she looked at Rick. "Lanie has an identification. And something she didn't want to tell us over the phone."

That was more like it. "Sounds suspicious." He stood up. "Do you think he's a spy? Poisoned by some rare and almost undetectable venom from a South American snake that only lives in the upper regions of the Amazon?"

Kate got to her feet, taking her leather jacket from the back of her chair. "We won't find out if we don't get there."

---

"Poison?" Rick asked, his eyes bright and hopeful as he stood with Kate in the ME's lab, a shrouded body in front of them, only the face on view.

Lanie Parrish shook her head. "Caisson Disease."

"What?" Kate looked confused.

Rick almost bounced on his feet. "You're kidding."

"Am I missing something here?" Kate asked.

"Decompression sickness," Rick explained before Lanie could get in.

"Decomp ..." Kate looked from her partner to her friend. "Don't only for divers get that?"

"Not exclusively. People flying in unpressurised aircraft can get it, as can extra-vehicular activity from a spacecraft."

"Are you saying he's an astronaut?"

"Or an alien?" Rick put in, but both women ignored him.

"No, in this case I can say pretty categorically he was a diver. From the damage to his joints, I'd say he dived on a regular basis." Lanie drew the sheet back so they could look at the body. She lifted one of his hands and they could see his wrist was swollen, the tendons gnarled like old wood. "And it's how he died."

"Lanie, he's not exactly close to the river."

"It can take hours for the symptoms to appear," Rick said. "If he came up too quickly, nitrogen bubbles develop in the bloodstream and can cause pain in the joints, headaches, vertigo ..."

"There's a whole host of symptoms," Lanie agreed.

"But not usually death."

"It happens, particularly when the diver's got underlying medical conditions." She picked up her board. "Patent foramen ovale."

"Bless you," Rick said.

"Which is?" Kate asked, glaring at him.

"It's a hole between the atrial chambers of the heart. Probably born with it." Lanie looked down at the body. "He shouldn't have been diving at all, since the pressure forced the bubbles into his arterial system. They were then trapped in his joints, causing extreme pain. Technically, though, he died of myocardial infarction."

"A heart attack. So you're saying this was natural causes."

"A bubble travelled to his heart, so that's cause of death. But I don't think it's the whole story." She looked at Rick. "Give me a hand."

The author was surprised. "What?"

"A hand. I pulled a muscle a couple of days ago in my back and I don't want to strain it."

"That's why you were ... less than polite this morning?"

"Just help." She moved the sheet back to reveal the dead man's torso, pale and clammy looking. "We need to turn him."

"But I'm not wearing gloves."

"Castle!"

"Fine, fine," he muttered, suitably chastised. "But if I catch something fatal, Alexis will sue."

"She can't," Kate pointed out. "You signed your life away. Remember?"

He glared at her, but gingerly put his hands where Lanie indicated, and between them they rolled the body onto its right side.

"There," the ME said, indicating a dark line just above the corpse's waist that ran for maybe a hand's width. It gaped a little, showing whiteness beneath.

Kate moved closer, peering intently. "Knife wound?"

"It ran along the rib. From the directionality, I'd say the assailant was aiming for his spine."

"There wasn't any blood visible at the scene."

Lanie shrugged elegantly. "He managed to dress it, or someone did it for him. His t-shirt was stained, but not soaked."

"So he was diving, came up too fast, managed to deal with the cut, then ... what, staggered some distance to where he was found?" Rick asked.

"Or drove. Or caught a cab. I'll get the boys checking," Kate said, still gazing at the knife wound. "This wouldn't have been debilitating?"

"No, Just painful," Lanie confirmed.

"Was he cut in or out of the water?" Rick wanted to know.

It was a good question, but Kate wasn't about to say so. "Lanie?" she asked instead.

The ME half-twisted, and only Rick noticed the slight wince on her face. She picked up a glass vial, a sliver of something black resting at the bottom. "Probably in," she said, turning it so it caught the light. "I found this in the wound – it's neoprene."

"A wetsuit." Rick looked at Kate. "Which explains why his underwear was damp. He gets attacked during or just after a dive, before he's had a chance to change. He gets away somehow, grabs his clothes and dresses without bothering to dry off first, finds a first aid kit to deal with the cut, then drives – or takes a cab – to where he was found." He paused. "But why go to that particular building?"

"Decompression sickness can affect the brain," Lanie said. "Confusion, memory loss ... it's possible he was planning to head home but just got lost."

"Which comes down to the other question." Kate stood upright. "You said you had an ID."

"Yeah." Lanie glanced down at the corpse's face, calm now she'd smoothed out the death throes. "He's in the system for half a dozen driving offences and a little weed smoking in college. Oliver Stanford." She handed over the copy of a rap sheet.

Kate took it, compared the image and the body in front of her, his short brown hair pushed back from his forehead instead of flopping forward, but undoubtedly the same. She scanned the details. "He's only twenty-five."

"Well, he's not going to reach twenty-six. There's an address in the Village," Lanie went on.

"We'll go take a look, see what might have got him killed." Kate smiled at her friend. "Thanks, Lanie."

"I'm still waiting on a few results, but if I find out anything else, I'll let you know."

Kate thanked her once more before she and Rick went back outside into the fresh air.

"That place always makes me light-headed," he commented as they walked towards the car. "All that formaldehyde." He grinned slightly. "Not that I mind. It reminds me of my youth." At her look he added quickly, "Chem class."

Her expression changed to one of yeah, right. "You could've stayed. I'm sure Lanie has a nice, cold, steel drawer all ready for you. It probably has your name on it."

He leaned on the roof, watching her as she undid the driver's door. "How can you be so cruel?" he complained.

"Proximity." She smiled and slid inside.

He growled under his breath, but got in next to her. "Actually, I was wondering how come we're still involved in this."

Kate turned the key, hearing the engine start immediately. "What is it, Castle? Don't want to look into the case of a man who died of the Bends on dry land? I thought you'd be all over this."

"Oh, I'm interested. I'm very interested. But technically he wasn't murdered."

"Not for want of someone trying, according to Lanie." Kate pulled the car out into traffic. "I think it's close enough that the Captain will allow us a bit of leeway."

Rick sat back, a smirk on his lips. "Good. Because I get the feeling this could be fun."

"Murder isn't meant to be fun."

"Maybe not. But that doesn't mean it isn't."

"Castle."

Just the one word and he wanted to sit back on his ass and beg for treats. Or a fondle around the ears. Or other parts. But mindful of those other parts being tweaked, pinched, punched or shot, he decided to shut up, so he just smiled at her and settled back into his seat, watching the world and the New York traffic go by.

Not that he could keep his lips sealed for long. "You haven't asked," he said conversationally as they drew up by a tall brownstone, flanked on the pavement by trees not yet showing the green mist of spring.

"Asked what?"

"About why it's called Caisson Disease."

She sighed. "If I shoot you now, will it stop you?"

"Probably not," Rick admitted. "I'd probably haunt you, whispering the answer in your ear as you slept."

"Then I suppose I'd better get it over with." The car safely against the sidewalk, she turned the engine off and twisted in her seat enough so she could face him. "So tell me, Castle. Why do they call it Caisson Disease?"

He was more than happy to oblige. "When they were constructing tunnels or bridges like the Brooklyn Bridge, they had to work below the water table, so they erected chambers, or caissons, which were sunk through the water to the river bed where they were able to dig the foundations without drowning. The caissons were kept under pressure to stop water flooding in, but the workers didn't know they couldn't just go straight outside. Fifteen men died building Eads Bridge from a mystery illness that they eventually realised was due to the high pressure inside the caissons, thus Caisson Disease." He waited for her to comment, but all she did was slide her eyes away from him and climb from the car.

Rick couldn't help the grin as he followed her, but he wiped it quickly from his face as he sidestepped a small poodle with a large woman on the end of a lead and joined her at the bottom of the steps. "Nice building," he commented, looking upwards.

"Are you going to give me chapter and verse on the architecture here as well?" she asked, one eyebrow raised slightly.

"Just saying."

"Well, don't." She turned on her heel and started up towards the front door in a swirl of leather jacket and the scent of cherries, knowing he was going to be right behind her.