The issue with sex, Kate Beckett decides as she sits on a plane to Toronto the next morning, is that it's addictive. Sex with Richard Castle - even more so.

It's not like she didn't have him begging in the shower last night (she did) and it's not like she didn't wake him up this morning by sliding down his body and taunting him with her mouth (oh yeah, she most definitely did). And yet sitting on the plane next to him, close but not close enough, is agony. Especially when he keeps giving her that goofy, happy smile, the one that crinkles his eyes and moves things inside her chest.

At one point he leans in close to watch the clouds in the window, the distant Canadian land spread beneath them. His warm breath skirts Kate's cheek, tingling; his shoulder presses heavily against hers and it's all she can do to keep her eyes from closing.

"Falling asleep on me, Beckett?"

Or not. Kate starts, her eyes flying open - damn - and she finds him looking at her with an amused, knowing smile.

He's doing it on purpose. He thinks this is funny.

Without thinking she shoots her hand down and cups him through his jeans, watching his eyes widen with a smirk. Not funny anymore, Castle? "I look asleep to you?" she husks.

So of course the next hour consists of Castle trying to convince her to join the Mile High Club ("It'll be fun, Beckett") and of her steadfastly resisting ("A tiny tiny bathroom isn't sexy, Castle, it's just uncomfortable"). She's relieved when they finally land in Toronto and get out of the plane, if only because it means there's more than five inches of tension-filled space between them.

The layover is only an hour and a half this time, so they go through customs and security and then grab sandwiches from one of those expensive airport places. They sit down and eat together in the terminal, keeping an ear out for an announcement about their flight, and of course when it's almost boarding time and Kate's about to suggest they head out to their gate, Castle decides he absolutely has to go to the bathroom.

She watches him hurry across the hall with a little sigh, starts gathering their things. It's not like they carry that much with them - they checked in their only suitcase - but still it's winter time and there are coats, scarves, her bag and his bag and did he really need to get his laptop out for fifteen minutes?

She shakes his head at him as she reaches for the computer, somewhat annoyed but also amused at the memory of his wide-eyed, little boy face ("Free Wi-Fi, Beckett! Why would you not use it?"). She closes the browser with a tight press of her lips that is really a smile in disguise, and she's in the middle of pulling his laptop shut when she pauses.

Wait. Those tabs he had up-

She only got a glimpse of them, enough to see his mailbox and twitter and whatever new social website he found his way to lately, but the last one...

No. Surely she's wrong. Why on earth would he - no. But she's already opening the computer again and pressing a finger to the space key, frowning as she waits for the screen to light up. When it does she pulls up the browser and goes to his history, clicking on the last handful of sites.

There's one - no, two, three - real estate websites in there, all of them with properties favorited, she sees as she looks into the first one. There's a modern-looking, luxurious condo on the Upper West Side, a restored brownstone with stunning woodwork, an absolutely lovely apartment in Greenwich Village that leaves her breathless.

What is he doing? Is he looking into buying something for Alexis? Kate wasn't aware that Castle's daughter was coming back to New York full time, but maybe-

"Hey, what are you doing? I thought you wanted to go to the gate-" Castle has come around their small table as he spoke and he stops at her shoulder, words and eyes arrested by the laptop screen. Kate arches an eyebrow at him.

"What is this for? You looking into buying a new place, Castle?" She's half-joking, hoping to tease the truth out of him, but he gives her a small, nervous smile.

"Right, about that. I was going to tell you about it," he says quickly, dropping to one knee so they're about even heights. "Once I found the right place. I just - wanted you to have the option, I guess, because honestly, who would want to live in a place where they were once recorded having sex by some kind of dangerous psychopath who later used those recordings to try and - I mean, I know I wouldn't. I don't even know that I want to stay there myself, honestly, after everything, so I figured maybe, you know, a clean start could be nice. Right? Just imagine - having a place of our own to make memories in." The words are coming faster and faster, his eyes pleading with her, and she's utterly speechless. "I mean, obviously, if you want to move in with me. I know we haven't - really settled that yet, so I understand, of course, if you don't-"

She cuts him off the only way she knows how, with her hand at his cheek and her mouth against his. She feels his soft sigh into her lips, the way he opens up for her, lazy and sweet, tentatively meeting her tongue with his; she nudges her nose to his and takes her time with the kiss, pours everything into it that she doesn't have the words for.

"Yes," she says when she lets him go, light-headed and yet somehow seeing it all so clearly, the path of their life together spread out before her eyes like a smooth, open road. "Yes, Castle. Yes."

He looks at her like he's holding his breath, like he can't quite believe her. "Yes?"

The hesitant light in his eyes, the tremulous smile make her feel like she's answering a completely different question.

And maybe, in a way, she is. "I'll move in with you," she promises with a stroke of her thumb over his lips, her fingertips timidly touching the joy that paints his face. "I want you too, Rick. Enough waiting." He opens his mouth but clearly she's left him wordless, because all he does is beam at her. She kisses him again, can't help it, those parted lips and all the beautiful words that she knows are stuck inside, but will find their way out in time. "Come on," she says with a smile. "We don't wanna miss our flight."

It's still winter in New York too, of course, but in comparison to Timmins it almost feels like spring to Castle. So he put on his favorite leather jacket this morning, a scarf that is so soft it probably doesn't contain any wool in it, and he resolutely ignored Kate's gentle warning that You're gonna get sick, Castle.

Now that they're walking out of the garage on 1st Avenue where they parked his car, he can feel the malignant chill of the February wind seeping into his (maybe) too-thin clothes, and okay, yeah, she might've been right. He's not going to admit it though. Instead he reaches for her hand and pulls her closer into his side, winds an arm around her waist to keep her there. His own private source of heat. The double meaning makes him chuckle, and he forgets for an instant the stark reality of their destination.

"What's so funny?" she asks, that lovely arch of question to her eyebrow.

He shrugs, not sure he can explain the detours of his mind, and he tugs her even closer, making her stagger and fall into him. She recovers her balance quickly, shaking her head at him, but the smile that lifts the corner of her mouth lets him know that he's forgiven - that she needs the comfort as much as he does.

They get to the bridge and start the slow climb up, cars and trucks roaring past, the rush of effort warming him. He's dropped his arm from her shoulders but he still has his fingers curled around hers, can feel her body warm and present at his side. The wind is harsher when they get to the top, Castle's eyes stinging with it, and he can't help tightening his grip on Kate. She's so slender, so light, and ever since they set foot on that damn bridge the picture that has been on replay at the back of his mind is that of her falling, falling, disappearing into darkness.

The walk is maybe not the only reason he's having trouble finding his breath.

It takes a while to get to the lift part of the bridge - the part that used to feature left, right and center in his nightmares - and they amble along in silence, each lost in their own thoughts. Or so he assumes until he looks over at Kate and finds her watching him, her eyes so rich and alive and attentive. He gathers a smile for her although he knows it won't be quite the real, genuine thing, and she smiles back softly in return, squeezes his hand.

He suddenly wonders which kind of personal ghosts she's facing right now, which memories she retains from that night. Was she conscious at all when she fell in the water? Did she try to fight off Tyson when he dragged her into the escape car that had to have been waiting for him?

"I don't remember much," she volunteers quietly, his questions probably written all over his face. "It's all a blur mostly. I remember the shock more than anything else, him hitting me and then falling and how - helpless it felt, I guess. And then intense cold, the water probably, clutching at me, wrapping around my bones. That's about it."

He nods stiffly, some tiny fragment of his distress from that night still lodged in his chest, making hard to breathe. Kate stops walking, pulling on his arm to make him still as well, and she wraps her arms around his waist, hugs him hard. He's a little surprised, but he's certainly not going to complain about it; instead he relaxes into her embrace, the close and steady reality of her in his arms. Her lips brush his neck.

"Here now," she reminds him, so strong, always. "Don't let it swallow you up, Castle."

Right. Right. He hugs her back, made stronger by her touch and her words, a faint echo of his conversation with Dr. Simmons resounding through him. He knew coming back here would be tough, and he's okay, he is. He just - has to learn how to breathe around it, how to build a life around the phantom of that night.

It takes them an extra ten minutes to get to the exact spot, the place where he spent hours waiting, waiting for back-up, waiting for the divers to resurface. Waiting for her to be found. He hasn't been here since that night but everything is still vivid, still raw and throbbing, and he rests both hands on the railing, finds his eyes drawn to the ceaseless flow of the river.

"Breathe, Castle," he hears Kate say at his side, and he releases an exhale he wasn't even aware he was holding.

Cars are still rushing past them unknowingly, each driver a perfect stranger with concerns of their own who might not even have noticed the man and the woman standing on Triborough Bridge on a grey February morning. Somehow the thought helps, makes it easier to keep sucking air in and out of his lungs. They're only tiny creatures, after all, little pieces of a much vaster universe, temporary, ephemeral. There will come a time when they're all gone and there will be no one to remember them, to remember that he or Kate or Tyson ever existed.

But whatever small time he has, whatever short segment of infinity - he gets to share it with her. Kate. And when it comes down to it, well, nothing else really matters.

"Give me that key," he says, holding up his open palm. She looks at him with a smile, proud and tender, her eyes so luminous in the morning light, and she reaches in her pocket for the locker key that Tyson sent her - ages ago it seems.

He takes it from her and in the same movement he lifts his arm and sends the key flying into the river, as far as he can. It draws an elegant arc before the water swallows it, the cars behind Castle covering any sound it might make, and he feels his whole body sag in relief.

Kate wouldn't let him throw the tapes in the river; audiotapes didn't biodegrade, she said, and Tyson had done enough harm as it was (which he had to grumblingly agree to). But she gave him this instead, gave him this moment on the bridge, and it's - he doesn't know how to put it into words, what it means to him.

In the end he does the next best thing: he curls a hand around her neck and tugs her up against him, brushes his mouth to hers, once, twice, and then a longer press that ends with a slow, deliberate slide of his tongue. She hums against him, their foreheads resting together for a few of his heartbeats, and he wants nothing more than this moment, wants to revel in her for the rest of his life.

"Home," Kate murmurs, her nose touching his. "Let's go home, Castle."

Beckett looks at her reflection in the mirror, smoothes a lock of hair, adjusts the strap of her dress over her shoulder. She likes that dress a lot, bought it last week on an impulse: the cut is perfect, the black fabric hugs her body like it was made for it, and the low, round neckline is both elegant and shows enough skin to keep Castle tantalized.

The heels will make her feet die a thousand deaths before the night is over, but they're worth it.

She exhales slowly, reaches for her eyeliner, changes her mind, slides the eyeliner back into her makeup case. Lipstick maybe? She's wearing a darker shade of pink that looks fairly natural on her, and it's really hard to tell whether or not it's wearing off.

She's still hesitating when Castle knocks on the ajar bathroom door.

"May I?" he says, his eyes meeting hers in the mirror. She smiles and opens the door wide, deliberately turning away from her image as she lets him in.

"Hey," she says, stepping into him and resting a hand over his chest. He's so warm and solid, and hers. "How's it going?"

"Good. Dinner's pretty much ready, table's set. I couldn't find my favorite wine glasses though, so we'll have to make do with the old ones."

"Hmm, have you looked in the 'kitchen' boxes?"

He smiles that wry, sexy half-smile, casually curling his hands at her hips. "I'm not sure you realize how many of those boxes I've packed already, Beckett. I looked into one and then gave up."

She huffs a laugh, inches a little closer to him. "Well, you're the one that got excited and had to start packing even though we're not moving for another month, Castle. I told you it was too early."

"It was not. It was in fact absolutely necessary to run outside and buy as many boxes as I could carry and then come back here to see how much stuff could fit into said boxes. It's called celebrating life, Kate. You should really try it. Also, have I mentioned how stunning you look tonight?"

She shakes her head at him but she can't contain her smile or the blush that heats her cheeks. "Thank you," she says softly, leaning in to kiss that beautiful mouth. He tastes like their dinner, a rich flavor of tomato with a hint of feta and maybe basil, and she's not sure what she's most hungry for - him or the food.

He nuzzles her cheek when they break apart, holding her close, and she winds both arms around his neck with a soft sigh. "You ready for this?" he asks, his voice a low rumble that coils her insides deliciously.

"Yes." Dinner tonight with Lanie and Esposito and Ryan and Jenny; she can do it. It'll be good, so good, seeing them after all this time. She's looking forward to it. "I am."

"Alexis's flying home tomorrow," he says, as if there's any chance she would forget that. She hums against his skin, lets her body sink into his. "You'd tell me if it was too much, yeah? If it gets to be too much, Kate."

"I'm fine," she sighs into his neck. "I promise."

He falls silent; there's only the lulling beat of his heart against hers, the smooth, rhythmical slide of his fingers in her hair, the quiet sounds of his breath. Kate closes her eyes for a moment, feeling like time has come to a halt, and of course that's when the knock comes at the door of the loft.

"That would be our guests," Castle says, and she hears the smile in his voice. So she untangles herself from him, keeping only his hand, theirs fingers entwined as she pulls him out of the bathroom and towards the rest of the world.

"Better not keep them waiting."