Disclaimer: All things "Castle" belong to the powers that be at ABC.

Author's Note: Written after re-watching 7x16, "The Wrong Stuff." I wanted to explore when and why Castle and Beckett each applied to go to Mars.

Tomorrow's Adventures

April 2012

Castle sighed heavily, closing out of the window showing his Twitter account, and glancing at the time.

3:16 am.

He should go to bed.

Why bother, another part of his mind retorted. It wasn't like actually going to bed would make much of a difference. It was the choice between sitting up in his desk chair, awake, trying not to think about Beckett while wasting time on the Internet and feeling miserable or lying down in his bed, awake, trying not to think about Beckett and feeling miserable. Either way, he'd be awake and miserable.

Or he would manage to fall asleep and he'd dream. His dreams now alternated between happy dreams—dreams where he visited the future he'd hoped to have, all he'd ever wanted, dreams of Kate smiling at him, dreams of kissing Kate, of making love to Kate, of Kate saying she loved him… And the unhappy dreams sending him right back into the observation room, of hearing Kate spit out the words that had shattered his world—I was shot in the chest and I remember every second of it. The stark, shocking realization that she had lied to him—Kate Beckett, champion of truth and justice, had lied to him for almost a year. Lied to him and only revealed the truth to a suspect as an interrogation tactic. That moment when he'd realized just what a blind, stupidly-optimistic idiot he had been. She had known all this time that he loved her and she hadn't said a word, had disappeared for an entire summer knowing that he loved her and still not contacted him at all.

He always jerked awake with the same sick feeling in his chest, his heart hurting all over again, as he relived that moment, the knowledge that she didn't love him pounding into him. He wasn't stupid. Or at least, not usually. He could read between the lines of an unacknowledged, completely ignored—and lied about—declaration of love to know that she didn't feel the same, couldn't feel the same. He had thought they were getting closer in these past months and in a sense, they had been. They were friends, after all, and partners. But in all these months, these years, that was all they had been—and he knew now, that was all they would ever be. So close but no further. Friends and partners but nothing more, never anything more than that.

Castle slumped back in his chair, closing his eyes. He was so damn tired. Physically exhausted from not sleeping well—and he was frankly scared of falling asleep at all because his dreams tormented him and he couldn't decide whether the happy dreams were worse than the unhappy ones or not. He managed to stay asleep longer for the happy dreams, always fought the return of consciousness, but it made the waking to the bleak reality that Kate didn't love him, would never love him, all the worse.

But he could deal with insomnia. He'd never been one for very regular sleep hours, not in years since the time when he would awaken to check on Alexis throughout the night or in later years, when he would stay up and write, words flowing from his mind and out onto the page until his fingers were cramped, or more recently, when he had gotten used to being woken up at all hours of the night by his phone to hear that a body had dropped.

So it wasn't physical tiredness. It was the emotional tiredness. Tired of hurting, tired of not being able to so much as think about Beckett, let alone look at her, without pain, tired of pretending he was all right to keep his mother and Alexis from looking at him with so much concern and sympathy in their eyes.

Tired of everything around him reminding him of Beckett. Because everything did. She was everywhere, seemed to have permeated every inch of the loft, which was odd since it wasn't like she'd really spent all that much time there. But that didn't matter—his vivid imagination, both the blessing and the bane of his very existence, supplying images of her everywhere. Everything he'd ever dreamed of, the simple, mundane visions of a life with her, tormenting him with the images of all the dreams he'd had that would never come true. He pictured her coats hanging in the front hall closet, along with several pairs of those incredible heels of hers. He saw her relaxing on the couch, eating meals with him and his family at the table, drinking coffee in the kitchen. He saw her curled up in a chair, reading in his office. And he saw her lying in his bed at night.

He shook the mental images out of his head—god, he needed to stop torturing himself like this—opening up a new window in his Internet browser, seeking a distraction. Anything to get his mind off of Kate.

News about one of the latest sci-fi shows, some mention of Leonard Nimoy, leading to one of the millions of websites devoted to Star Trek, leading to a random decision to visit NASA's website, leading to…

Castle straightened up in his seat, feeling the first spark of real excitement that he'd felt in weeks.

Viggo Jansen, the billionaire entrepreneur, was launching a project called Mars 2018. And he was taking applications for people who were interested in being among the first group of humans to go to Mars.

Mars. Space. The final frontier.

Castle clicked to open up the application.

Mars. And maybe that could finally put enough distance between him and Beckett that he wouldn't think of her every minute, wouldn't see her everywhere he looked, wouldn't dream of being with her. Vegas hadn't been nearly far enough, hadn't done any good. But maybe, perhaps Mars would be far enough.

He let out a rather bitter little laugh. He'd sometimes thought that Kate Beckett seemed to exert a sort of gravitational pull, drawing him in, keeping him near her. Through bombs, snipers, near-drownings in the Hudson, CIA conspiracies, and endless summers spent apart, they'd always found their way back to each other. So maybe this was what he needed to do to break free of her—literally leave this planet and travel to another.

Mars should be far enough that he'd be able to begin to forget her and move on. Right?

July 2014

Being shot in the chest had hurt so much less.

Kate stared at Castle's picture on her makeshift murd—she flinched away from the word—story board on the shutters in her apartment. Castle's disappearance board. All the pictures, the little post-its of what she and Espo and Ryan had managed to find so far. All… next to nothing of it.

She stared at Castle's picture—his so-familiar face, the small smirk curving his lips—and she flattened her hand against her chest, just over her heart, over the scar of where she'd been shot, as if somehow that would make this hurt less.

Her scar hurt, burned, at times, until she could swear she was feeling the bullet hit her all over again.

It was psychosomatic, she told herself—or so Dr. Burke had told her. Her mind playing tricks on her to make her believe she was feeling again the worst physical pain she had ever felt in a weird echo to this worst emotional pain she'd ever felt.

A sob escaped her and she curled up in her chair, her chest heaving as she cried.

Oh Castle, Castle, Castle…

She was trying to be strong, to be extraordinary as he'd always said she was, but god, she sometimes thought that this, losing Castle, might finally be what broke her.

She missed him. She needed him. And if she'd ever doubted just how true that was in the past couple years since she'd finally acknowledged to herself—and then to him—just how she felt about him, she couldn't anymore. She needed him with her, needed his smile to brighten her day, needed his humor and his silliness to balance out her own seriousness, the darkness that was her job. She needed his steadfast faith in her to give her strength, needed his arms around her to give her peace. She needed his sharp intelligence and creative thinking for when her own mind seemed to be stuck going around in circles.

He was missing. He wasn't de—gone. Not forever. He couldn't be. She clung to that, told herself that with every hour, every day, that passed by with no word, no further news.

He was being held somewhere by someone. He hadn't left her.

He was alive and they would find him again.

She had to believe that. She had to.

But with every hour, every day, that went by, she found her hope flickering, fading, little by little.

It had been more than six weeks now. 6 weeks, 4 days, 17 hours since she'd spoken to him on the phone, heard his happy, excited voice. 6 weeks, 4 days, 17 hours since she'd really smiled or laughed.

The FBI had long since stopped their search, concluded that Castle was missing because he wanted to disappear.

Her eyes automatically went to the grainy, somewhat blurry picture of him dropping the money off in that dumpster, her mind automatically replaying the video of him doing so. The video that had broken her heart even as she couldn't quite believe what she was seeing.

No, no, no, there was something else going on. There had to be. Castle loved her. She knew that. She'd seen it in his eyes, felt it in his touch, heard it in his voice. He loved her—she heard his voice in her head, always—and blinked back yet more tears.

"Always," she whispered and the word was a promise, a vow, that seemed to linger in the empty room. And Kate felt somehow, irrationally, comforted, as if he could hear her. And she could certainly picture the look in his eyes, the curve of his lips, whenever she'd said the word to him.

She opened up the Internet browser, settling in for another long hour of searching—looking for anything, anything at all, that might lead to him. It was one of her rituals, every night, in the slow stretches in the middle of the night. Visiting his own website, first, and then his various fan-sites, glancing through the many posts from his fans of "Richard Castle sightings." She made notes of the ones—a very, very few of them—that seemed like they might potentially lead to something useful, something for her and the boys to look into the next day.

She stopped when her eyes started to blur, the very words on her computer screen seeming to run together, but she only leaned back in her chair and closed her eyes for a minute.

She was exhausted. She didn't think she'd slept a full night in weeks. Hadn't slept more than a couple hours at a time in 6 weeks, 4 days, and almost 19 hours now.

But she wouldn't go to bed, knew she wouldn't be able to sleep. And if she did, she would dream. Dream that he was back, holding her in his arms, smiling at her with that smile she only ever saw when he was with her or with Alexis. Or she would dream of finding his body.

She was trying, so hard, to keep hoping but with every hour, every day, that passed by without any word or sign, it got harder and harder to believe that she would ever see him again. She knew him, knew how smart he was, how resourceful he was. She knew that he would move heaven and earth to come back to her, to his family, and even if he couldn't escape himself, he would find some way of contacting them, to let them know he was alive.

But there had been nothing. Not the smallest indication that he was even still alive. And her rational self, the part of her that needed real, solid facts and evidence to back up anything, was finding it harder and harder to believe that Castle was still alive.

She shuddered and her eyes snapped open, sitting up. No, no, no, she wouldn't think like that. She couldn't think like that. She couldn't give up.

She skimmed through some news sites, CNN, others, for any mention of him—maybe the one benefit of Castle's fame was that his disappearance had made the news, made the likelihood that she would hear and find out any information much higher. He was famous—somewhat famous, an errant voice in her head inserted, and she bit back a sob at the memory of the times she'd teased him about that—surely someone, somewhere, would see him, would know something.

Her tired eyes caught on another famous name, a word. Sir Ian Rasher was looking for people to volunteer to go to Mars.

Mars. She felt a small, poignant smile curve her lips. The Castle that had taken up residence in her head gave an excited bounce—both painful and comforting at the same time, because it let her pretend he was still there with her, beside her—she knew how he would react to things, could guess what he would say or do.

A chance to go to Mars. Oh, yes, she knew how Castle would react. He would love it. She could just hear his voice, intoning the words, "Space, the final frontier… To boldly go where no one has gone before," imitating the opening monologue from Star Trek, the way he had whenever they had watched Star Trek together, the way he had when they had worked that case involving Nebula 9 at the Super Nova Con.

Oh, Castle would leap at the chance to go to Mars.

For the first time in weeks, she felt a small laugh escape her as she remembered his confession a few years back about how recently he had bought his property on the moon.

A chance to go to Mars—on a sudden impulse, Kate clicked to open up the application.

She would apply and in some small way, she felt… closer to him because she knew it was what he would do if he were here. She knew that, knew Castle wouldn't miss out on this chance.

She didn't really think she would be accepted or even if she were, that she would go—she couldn't leave without him and if Castle was still gone, she couldn't leave her father or Alexis and Martha—but she would apply because it was what he would do if he were here. She would apply because it was also the sort of thing she would do for herself if Castle were here, now that she was braver, now that Castle had made her stronger, opened her up to be silly again, to dream again. He had jokingly told her once that he would give her the moon if she wanted it—and (somewhat) more seriously, promised that he would add her name to the deed of his property on the moon. He might not have given her the actual moon but he had given her back her life, had given her back her sense of adventure. And there could be no bigger adventure than going to Mars.

She filled in the application form.

Because it was what he would do if he were here.

Because she knew the way the idea of going to Mars would make him light up with that childish excitement that was so much a part of him.

Because it was the sort of life he would still want her to have, unafraid of the future.

But when she was finished with the application, she covered her face with her hands and cried, again, sobs shaking her shoulders. Aware that no matter what she did, no matter how she was trying to stay strong and brave and unafraid of tomorrow, she was faking it.

All her defensive walls had crumbled; Castle had forced his way inside her walls and then helped her take them down, brick by brick, and made her hope again, believe again in love and happy endings, and now, without him, she was broken.

March 2015

Kate tore off a piece of the naan they had ordered that had just arrived and popped it into her mouth, chewing and then swallowing.

"Castle, when exactly did you apply to go to Mars?"

Castle had just taken a drink of water and he paused before setting the glass down, his expression abruptly sobering. "It was after the Boylan Plaza bombing a few years ago."

Oh. Kate sobered at the mention of those painful weeks. They had talked about it since then but it didn't make the memory of those weeks much easier to think about, those days when she'd thought he'd given up, when she'd believed that he didn't love her anymore. She hated to think of that time, of how close she'd come to losing him through her own cowardice and weakness and inability to talk about her feelings. And she knew the memory was just as painful for him, could see it in the way his eyes darkened, the bright blue dimming, whenever those weeks were mentioned.

He looked down at the table and then back up at her. "It was the middle of the night but I couldn't sleep and I saw the application for Mars 2018 and… at the time, I wanted to get away and I thought Mars might be far enough."

"Far enough for what?" she asked, although she had a feeling she already knew the answer.

"Far enough that I could begin to forget you," he answered honestly, reaching across the table to grasp her hand to soften the blow of the words.

"Oh." She laced her fingers with his, tightening her grip on his hand. It was ridiculous—she'd been expecting the answer and she knew he had never actually succeeded in forgetting her, but it still hurt to hear the words, to know he'd wanted to forget her, to think of how far he'd been willing to go to try to forget her.

"It wouldn't have worked," he told her with sudden intensity. "I knew that, even back then. I'd never be able to forget you." He paused and then added with a softening of his expression, "It's like our song says. 'You're in my veins and I cannot get you out.'"

She leaned across the table and dropped a quick kiss on the corner of his mouth for that.

She drew back, sobering. "It's almost funny. You applied to go to Mars to get away from me and I applied to go to Mars to feel closer to you."

He blinked and frowned. "Where was I that you wanted to—" he broke off abruptly and she knew he'd figured it out, saw it in the way his expression changed, in the sudden tension in his frame. "God, Kate, I'm so sorry."

"It's not your fault, Castle. You didn't choose to leave." He hadn't chosen to leave her, but she left that last part unsaid.

"It doesn't mean I'm not still sorry. I… I hurt you and I can't stand the thought of that."

"Ssh, Castle," she murmured, leaning over the table to brush her lips against his again, silencing him. "It's okay," she told him. And it really was. She still had the occasional nightmare about the time he was missing, still felt the fear rise up inside her, grip her heart, too quickly, whenever they were apart for any stretch of time. But then she would see him, would see his smile, the tenderness in his eyes, feel the warmth of his touch. She would see the ring on her finger, the ring on his finger. And the warmth, the happiness, would bubble up inside her again, banishing her fears, her doubts. "You came back; you're here now. And that's all that matters."

"You're amazing, you know that?" was all he said in response.

"You're biased," she retorted promptly, giving him a teasing quirk of her eyebrows, even as she felt her heart flutter a little at the look in his eyes. She didn't think she'd ever get over it, how he, who knew her so well, who knew her faults and her weaknesses, even after all these years, still looked at her with that touch of awe.

He shrugged a little. "Guilty as charged."

She hid a small smile at his easy admission of being biased in her favor.

"I applied because it would be an adventure," she admitted quietly, after a moment. "It would be an adventure and that feeling of not being afraid of adventures was what you taught me and I knew going to Mars was something you would want to do too."

"Kate…" he let out a shaky breath.

She forced a small, rather wobbly smile. "And I think part of me thought that… you'd come back because of it, because you'd never let me go to Mars alone. It was silly of me…"

"No, not silly," he interrupted, gently. "Human. People believe what they need to believe in order to get through hard times and if applying to go to Mars helped you to stay strong, then I'm glad. And you weren't wrong. I would go to Mars with you. I'd go anywhere with you."

"I know you would," she said simply. And she did know it. She would always be a skeptic and a cynic, quick to doubt in many things, but she trusted him, believed in him. She believed in his love and his loyalty the way she believed in her mother's memory and her legacy; it was the bedrock, the stable foundation of her life.

She managed a smile, wanting to lighten the mood, wanting to see him smile. "But I think I'm having second thoughts about going to Mars. Almost dying in the simulation took some of the charm out of the idea. Besides, it occurs to me that Mars might not be the best place to raise little kids."

His eyes shot to hers at the mention of kids. "Kids?" he almost croaked.

"I told you I've been thinking about it." She gave him a small grin that missed being insouciant by a mile. "I want little Castle babies."

"Kate," he breathed and then he leaned across the table to kiss her, rather more deeply than he normally would in such a public setting.

The sound of a throat clearing had them breaking apart to see that their waiter had returned with plates of their food and was carefully not looking at them.

Kate felt herself blushing as she hurriedly straightened up, scooting her chair a few inches away from Castle's, the better to avoid temptation. Because he was looking at her with those blue, blue eyes of his, gone dark with desire, and his lips were… She blinked and forcibly focused her gaze on the food. Dratted man, she couldn't take him anywhere—and how was it possible that even now she couldn't so much as look at him sometimes without simply wanting to climb into his lap, never mind that they were in public?

She bit her lower lip to keep her laugh from spilling out as she nudged Castle. "See what you did, now we're making a scene."

Castle narrowed his eyes at her but waited until after their waiter had put down their plates and left again before he huffed, "What I did? It's your fault. You can't say something about wanting to have my babies and expect me to keep my head."

She smirked at him. "Fine, then. All talk about babies will be reserved for when we're at home."

He pulled a face at her and pushed the curry dish closer to her, since he knew how she liked it while she passed him the rice dish. As usual, he proceeded to make a mess of his plate, mixing up all the different things they'd ordered. She sometimes thought that Castle had never outgrown the eating habits of a teenage boy with his penchant for mixing foods and eating outlandish combinations, his notorious s'morelette only one example out of many.

Unbidden, the thought darted into her mind that their kids, when they were going through the messy-eater phase of throwing food around, were going to be absolute nightmares, if Castle's grown-up example was any indication.

She froze for a fleeting second, her mind distracted by the mental image of a baby with Castle's blue eyes, grinning gleefully as he flung a spoonful of baby food to the floor.

She blinked, returning to the present to see that Castle had paused to lift his eyebrows at her.

"What is it, Beckett? You look a little funny."

"Careful, there, that's my face you're talking about," she quipped, automatically resorting to their usual fallback of teasing, before she admitted, "I just… I was picturing a baby," she admitted. Their baby. She'd been picturing their baby—and the sudden rush of emotion she'd felt surprised her. Yes, she'd been thinking about kids but it had until now been something a little… intellectual, hypothetical, involving planning and wondering and mentally debating with herself. Questions and doubts and fears, both practical and emotional. For her entire adult life, since the day she'd lost her mother, the thought of ever having kids of her own had been relegated to the status of a pipe dream, something that was simply not an option in her life so she'd never even allowed herself to think about it. It was only in the past couple years, only thanks to Castle, that she'd started to dream again, to let herself hope again. But even so, even with Castle, she hadn't seriously considered having kids—not while Bracken was still out there. The situation, everything involving Bracken, was unstable enough without throwing in the added factor of children, of some small, so-fragile, so-precious human being entirely dependent on her and Castle for everything. But now, she and Castle were married; more importantly, they were… happy, settled. Safe, with Bracken and even Jerry Tyson gone for good. The mental image of a baby, their baby, returned to her mind and oh… This, now, this was… sheer want. A surge of wanting, of longing, that was stronger than anything she'd ever felt before except for when she'd started picturing a life with Castle, marrying Castle.

He stilled, putting down his fork with preternatural care, and she hurriedly added, "Sorry. I know I said we'd save any talk about babies for when we're at home. This can wait. Let's just finish eating."

He caught her hand with his. "Oh, no, Kate, I couldn't possibly focus on food with something like that hanging in the air."

She glanced around, biting back the sudden urge to laugh. Oh god, were they really about to have this conversation in a crowded, loud Indian restaurant?

Well, they never really could do anything the normal way, could they?

She let out a breath, turning so she could face him directly. "I… I want to have kids with you. I think… I'm ready to have kids with you." He was silent and she hesitated, rushed on, "I mean, if you want… I don't…"

He cut her off by pressing a finger lightly against her lips before moving his hand to cup her cheek in one of his habitual tender gestures, his thumb softly brushing against her lower lip. "I want," he finally managed to say, his voice not quite steady, "God, Kate, of course I want kids with you."

She smiled, the extent of her relief, her joy, surprising her a little. "Okay, good," was all she managed to say, rather inanely.

He smirked and then he laughed out loud—damn, irritating, smug man. "Silly Kate, did you really think for a second that I would say no?"

She lifted one shoulder into a half-shrug, feeling a little sheepish. He'd made a few throwaway comments over the past couple years about kids but they'd never seriously talked about it, whether he wanted more kids, to go through the whole exhausting process of taking care of a baby all over again. Sure, they had taken care of little Benny in that case over the lottery but they'd both known that it was only a temporary thing and yes, she'd promised that if they ever had kids, she wouldn't let him do all of it alone, but that had been more than a year ago now. And then with his disappearance, his lost memories, that she knew still haunted him, she just hadn't been sure.

"Kate, I've been dreaming about having kids with you for at least three years now, probably longer."

She felt her heart flutter a little, the way it usually did whenever he so casually referenced just how long he'd loved her, how easily he admitted now how certain he'd always been of his feelings for her and the depth of his commitment to her, to their relationship.

"Three years, Castle, really?"

"Don't give me that skeptical look, Beckett," he returned lightly. "Just because I didn't mention it to you back then doesn't mean it isn't true. But I figured walking up to you one day in the precinct and telling you that I wanted to raise a family with you would be a quick way of ensuring that you'd run away so fast that you'd have been a blurry speck on the horizon before I could blink."

He spoke teasingly but she felt a small pinch of guilt at how true the words were, the reminder of how long she'd made him wait. Oh, she really, really did not deserve this man and his devotion, his patience, his love. Her throat was suddenly tight with emotion but she swallowed it back—this wasn't the time or the place for it—and instead quirked her eyebrows at him teasingly. "Are you sure you don't mean dreaming about the act of making said babies?"

"Kate Beckett, get your mind out of the gutter," he huffed in mock disapproval before he waggled his eyebrows at her. "You know perfectly well that I've been dreaming about doing that act with you since the moment we met so that's been part of my dreams for much longer than only three years."

She had to laugh, as she knew he wanted her to, before she sobered. "So you don't mind if we… start trying?"

He gave her an exaggerated leer. "I'd be up for trying to make a baby with you right now if you wanted to."

She laughed, blushed, and nudged his shoulder. "Behave, Castle, we're in public." She glanced around, making sure the noise level in the restaurant would drown out her words, and then leaned towards him, lowering her voice. "But when we get home, I'll throw out my pills and we can start trying."

He groaned softly and then blurted out, "Eat fast."

She laughed again but she did start to eat again, as did he, although he retained his grip on her hand.

She let her mind wander a little, more visions of a baby, their baby, crowding into her head. Castle, holding their baby protectively against his broad chest the same way he cradled little Sarah Grace Ryan whenever they saw her. Castle, hanging over a crib to watch their baby sleep. Castle and her marveling over their baby together.

And she smiled.

Going to Mars would be an adventure but Kate was suddenly sure that having a baby with Rick Castle, raising a family with him, would end up being the best and greatest adventure of her life.

~The End~

A/N 2: Obviously, the song Castle quotes is "In my Veins" by Andrew Belle.

I didn't intend for this fic to turn into a conversation about babies but it just ended up happening.

Happy Passover/Easter, to those who celebrate. Thanks for reading and please review!