Alternate Universe, set somewhere in Season Three. If everyone else knows it's not if Castle and Beckett will get together but when, then why can't they figure it out too?

Rick knows what the look on her face means. He knows why her eyebrows gather over eyes that are wet without her permission. He understands why she swallows heavily and then chews her bottom lip. He even understands why her breathing is slower because it's shaky, trembling the way her hands are as she types out the report. The tap tap of her fingers on the keyboard fills the silence they haven't broken since she tried and failed to plug Damon Sutton's carotid artery.

Right now, she's not the Beckett he works with every day. She's the Beckett he's not supposed to see but does anyway, in rare glimpses that escape like winter underneath a doorway. He wants to hold her and rock her the way he used to rock Alexis when she was scared. At least then he'll feel like he's doing something.

She clears her throat as if she can force away the emotion that's clogging it. Her attempt to maintain some semblance of detachment after the day they've just had makes him acutely aware of the injustice of the world. Kate Beckett has had more than her fair share of tragedy. She shouldn't have to face any more.

He opens his mouth to tell her to stop trying so hard to hold it together, but she speaks first.

"I'm tired," she says softly. She pushes her hair away from her eyes. She doesn't look at him. "I'm going to finish this tomorrow."

She stands slowly and Rick gets to his feet too. "Let's get a drink," he suggests, though he already knows the answer.

She pulls her coat off the back of her chair and gives him a polite smile. "I'm tired."

"Let me take you home," he tries again, reaching out to help her put on her coat.

She lets him help her. "I can get home on my own, Castle."

"But what about ninja assassins?" She gives him the incredulous look he was hoping for. "They lurk the streets of New York," he explains. "Undercover ninja rings. Like poker." She rolls her eyes. "There's aliens too," he continues. "They'll beam you up and put a tracking device in your neck. You have a lovely neck, why ruin it?"

"I'm armed. I'll take my chances."

"But they have ray guns," he protests. He's really hoping she'll smile, even if it's at his expense. "And sticky fingers that suck out your life juices." He spreads his fingers out wide in a number five gesture and then pretends to suck out her life juices, complete with sound effects.

She finally smiles, but it's not the smile he wants to see. It's dim and forced. The smile he wants is nothing but bright and free.

"Good night, Castle," she says. She brushes past him and toward the elevator. He watches her go. When she's out of sight he sinks into her chair. He spins in it for a while, examining the precinct from Beckett's point of view. Eventually, he fishes his phone out of his pocket and hits the first speed dial. It goes straight to voicemail.

Hi guys, its Alexis. I can't come to the phone right now, but…

Date, he remembers belatedly. She's on a date. He sighs and hangs up. He thinks about calling Gina. He's planning what to say when he's caught off guard by the sight of something on the corner of Beckett's desk. He leans forward and pushes her standard-issue desk lamp out of the way.

The nesting dolls he bought in that little Russian shop ages ago during the baby-swapping case are lined up at the back of her desk. He's never seen them there before. Have they been there since he bought them? Has she kept them all this time? Usually when he's near her desk it's because she's there, and he's too busy focusing on her to pay attention to her desk. But she's not here now and there they sit, staring at him.

His thumb hovers over his phone, ready to dial, but he can't. He's frozen in Beckett's chair, staring at the nesting dolls and thinking about Damon Sutton's blood all over one of her favorite blouses. He's haunted by the look on her face when Damon stopped twitching; what it must have been like to feel his heartbeat under her fingers one second, and then nothing the next.

Permanently engraved in his memory is the breathless shock of witnessing death firsthand, followed closely by the shock of Beckett reaching for him. With her hands covered in blood and tears sitting in her eyes, she clutched his arm and shuddered. He did the only thing he could. He wrapped an arm around her shoulders and pulled her against his chest. When she buried her face in his shoulder, he kissed the top of her head.

He leans forward and grabs the smallest nesting doll. He knows what he has to do.

X-X-X-X-X

He's standing in front of Beckett's apartment door, his fingers wrapped around the nesting doll in his pocket. He isn't sure this is the best idea. She's tired and upset and so is he, enough that he might do something stupid and she might reciprocate. They're both in relationships, and while he doesn't know much about hers, he knows his is a goddamn rollercoaster.

There are moments with Gina when he remembers why he fell in love with her. Why he still loves her, though it's different and less intense than when they were married. It's different because of Beckett. He knows that and so does Gina.

The fights remind him of why he fell out of love with her. The roller coaster of love and hate never seems to end with Gina. Standing in front of Beckett's apartment door makes him realize that he's on a roller coaster with her, too. But it's a different roller coaster. The good kind of different. Good enough that he always ends up outside of her door, literally and figuratively.

He knocks. As he waits, he fiddles with the nesting doll in his pocket. For a brief, absurd moment, he imagines that the doll is Beckett. When she opens the door his breath catches in his throat. He isn't prepared to see her like this.

In his daydreams, he sometimes fantasizes about Beckett opening her door in a tight red teddy. Sometimes it's black leather, right after a ride on her bike. Other times it's nothing but a towel and wet hair, which falls in perfect waves around her bare shoulders.

She doesn't look like the Beckett of his daydreams.

All her clothes are too big for her. She's thin anyway, but since everything she's wearing is oversized, she looks small and vulnerable standing half behind her front door. The gray crew neck sweatshirt with NYPD written across the chest in faded blue lettering hangs down to the middle of her thighs. Her shorts are white, with a small black knit Nike swoosh just above the hemline, which is well past her knees. They have to be men's shorts.

Rick looks up at her face in surprise only to realize he has to look down, because barefoot she's much shorter than she is in power stilettos. Her hair is gathered into a messy ponytail. He stops short when he sees that there's a very thin rim of black underneath her eyes, as if she's been swiping at tears and her mascara is collateral damage.

"Castle," she says. She's surprised, but the tone of her voice tells him she's a little bothered too. He wonders if it's because he can tell she's been crying.

"You could wear that as a dress," he tells her.

She frowns. "What?"

"That sweatshirt is too big for you."

She ignores him. "What are you doing here?"

"I can buy you one that fits, you know. I can buy you a dozen that fit."

"I can buy my own clothes."

"Obviously not if you're getting sizes eight times too-"

"It's not mine," she interrupts. The second she says it she looks like she regrets it.

"Whose is it?"

"Royce," she answers after a pause. The surprise he feels must have flitted across his face, because she lifts her chin like she's daring him to be brave enough to ask how she got it. He isn't.

"Those his shorts too?"

She looks down at the shorts, and then back up. "No. Josh."

They stare at each other for a long moment. It usually doesn't happen like this. Mentions of Josh usually don't make the atmosphere tense, because they've got an unspoken understanding. Gina is his girlfriend and Josh is her boyfriend, but that doesn't change them. Whatever they are.

"Note to self to keep an eye on my clothes."

He's rewarded with a small, amused smile that is more than he could have hoped for and exactly what he wanted. He knows that the grin he returns is probably goofy and idiotic but he doesn't care.

"Is Josh here?" he asks, because whether he needs her or not, he won't interrupt.

Beckett shakes her head. She leans against the door, resting her temple on the wood. "I'm alone."

He smiles. "Me too."

She doesn't say anything, and that's when he hears the TV. "I'll take Shakespearean Kings for 200, Alex."

"What are you doing here?" she asks, unaware of the TV.

"'My kingdom for a horse'," Trebek reads.

"Who is Richard III," Rick answers.

"What?" Beckett says, her forehead creasing into a frown.

Rick nods over her shoulder. She turns toward the inside of her apartment just as a contestant says, "Who is Richard III?"

"That's correct," Trebek says.

Beckett turns back toward him. "Show off."

Rick smiles. "I thought Jeopardy was on at 7:30?"

"It's a marathon on the Game Show Network. What are you doing here?"

"I wanted to challenge you to a Jeopardy duel. You should know in advance that you have no chance of winning."

She lifts an eyebrow. There's a long pause.

"I thought you might need me," he tries again.

Now both her eyebrows lift. There's another long pause.

He exhales slowly. "Other way around," he admits honestly. "I need you."

That must catch her off guard, because her eyebrows fall and she presses her lips together. He's thinking about Damon Sutton again and he knows she is too. She swings the door open.

"You want to come in?" she murmurs.

She doesn't have to ask twice. As she closes the door behind him he takes stock of her apartment. Jeopardy is still playing on the TV, and there's a bottle of wine on the coffee table in front of the couch. A nearly empty glass is next to the bottle along with three cartons of Chinese food and a pair of chopsticks. There's a blanket crumpled on the corner of the couch. Rick imagines what she looked like before he knocked on the door; curled up under the blanket, alternating between chopsticks and the glass of wine while she shouted Jeopardy answers at the TV.

"I wasn't expecting company," she says. When he turns his head toward her voice he sees that she's standing next to him, also staring at the couch.

"Do you want me to go?"

She looks at him. "Did I say that?"

"I'm trying to be considerate."

"Since when?"

He puts his hand over his heart. "That stings a little."

"Only a little?"

"I bounce back quickly. How else do you think I've survived all this time with you?"

She snorts. She's standing close to him, close enough that he feels the attraction vibrating underneath his skin. They're not at work, so there's no buffer.

"Do you want some wine?" she asks.

"Yeah. Please."

She walks around the couch and plucks the bottle and her glass off of the table. He follows her into the kitchen and watches her stand on her toes to reach into the cupboard. She pours until the glass is half full of crimson liquid and then holds it out to him. He takes it from her and sips slowly.

She moves to the other side of the kitchen, maybe to put some distance between them. Maybe she felt whatever was thrumming in the air too. She's watching him, her eyes trailing over his face. When he leans against the edge of her counter and meets her eyes, she takes a sip from her own glass. He sees that she's got her hands inside the sleeves of her sweatshirt, so that only her fingertips are peeking out. Something about it reminds him of a child, and it only makes her seem more vulnerable. Smaller.

"What's wrong?" she asks him.

"You."

"Me?"

"You're not okay. Not after today."

"You came here to tell me I'm not okay?"

"I came here to tell you I'm not okay either. And because I thought we could be not okay together."

She tilts her head sympathetically. "How not okay are you?" she asks him softly.

Rick feels his throat tightening. He contemplates how honest he wants to be with her, and realizes that if he wants honesty from her, he better give it to her first.

"When you shot Coonan it was the first time I'd watched someone die. But I was so worried about you, and I hated him so much, that I don't think it really hit me."

His throat is still tight, and suddenly he can't look her in the eye.

"Damon Sutton hit you," Beckett finishes for him.

Rick nods, relieved that she knew what he was trying to say. He still can't look at her. "I must've written about death a hundred times. But I never imagined that's what it was like."

There's a long pause, and then Beckett crosses the kitchen to stand next to him. She finishes the rest of her wine, and sets her glass in the sink. Then she puts her hands on the counter and leans over them, her head bent as if she's staring down into the drain. Rick looks back down into his wine glass.

"The first time I killed someone I was still a beat cop," she starts quietly. "Royce and I got called in as backup for a shootout. We got separated right off the bat by gunfire. A little while later, when I came around a corner on the second floor, I saw Royce on his knees. Some thug had a gun to his head. I had to shoot."

Rick looks over at her. She hasn't moved.

"So I did. I don't think I'll ever forget the look on his face as he died."

She stares into the drain for a little while, as if she can see the man's face again. Finally, she lifts her head to look at him.

"How'd you deal with it?" he asks.

"About the same way you are. I showed up at Royce's apartment at three in the morning drenched because I walked there in a storm." She smirks at him and pulls at her sweatshirt. "That's how I got this, by the way."

"I didn't ask."

"You didn't have to."

They share a smile, and then Rick sobers again. "What did Royce say?"

She turns her body toward him, leaning her hip on the counter. Her eyebrows gather in thought as she crosses her arms over her chest. "He poured me a glass of scotch and told me about the first time he killed someone."

Their eyes meet, and for a while all Rick can think about is the sound of her voice when she said I was in love with you to Royce on the phone.

"I don't know how you do it," he practically whispers, as if talking any louder will break the intimate bubble that's surrounding them.

"Do my job?" she asks.

He nods. "For me, there's the consolation that if I had to, if I couldn't take it anymore, I could walk away. But you can't do that. Or won't."

"Or both," she adds.

He nods. The wine glass feels heavy in his hand, but he doesn't put it down. "Does it ever get easier?"

She laughs humorlessly. "I hope not. Because if it does, then I'm more like one of them than I ever wanted to be."

She's breaking his heart, the way she's talking so softly and leaning against the counter like it's holding her up. She always seems so much larger than life, so invincible, but in her dimly lit kitchen with clothes that are too big and dark circles under her eyes, she's never looked so human. So fragile.

"So how do you do it?"

"Compartmentalize," she says with a shrug. "I have days where it hits me like it's hitting you."

"How often?"

"Every now and then." She looks at the sink again, back down into the drain, but her body is still facing him. "Sometimes I feel like I'm pushing this massive boulder up a mountain. And when I finally get to the top and I'm about to rest, it rolls down the other side. So I go down, and I start pushing again. But when I get it back up to the top, it just rolls down again."

Rick stares at her until she finally looks at him. "I could push it for you."

She smiles sadly. "It's not your boulder to push."

Rick moves closer to her, and she tenses the second he invades her personal space. "I worry about you sometimes."

"You shouldn't."

"Someone should."

"Not you."

He stares at her, wants to ask her so badly why not him, but he doesn't. Partly because he knows the answer, but mostly because she looks so terrified that he can't bring himself to say it. The second he makes the decision to let the moment pass, he reevaluates it. So what if she's scared? He is too. He's fucking petrified, and that's how he knows it's right. He's never had to be better, never had to be the best he's capable of. Never until Kate Beckett. There's a reason he's here and not somewhere else, and after today he's not sure he can ignore that any more. Maybe Damon Sutton is just another murder victim, but maybe he's something else, too.

"You were shaking," Rick says. "Before the paramedics and the boys got there, after Damon died. When you let me hug you. You were shaking."

"So were you."

Rick swallows carefully around the lump in his throat. "I didn't want to let you go."

He hears his words come back to his ears and is stunned by how scared he sounds. Maybe he should be worried that he's not coming off incredibly manly, but he's not.

She bites her lip. That drives him crazy, it always has, and before he knows it he's reaching up to run his thumb along her lips so lightly he can barely feel her under his fingertip. After staring at him for a moment she turns her face away.

"You shouldn't be here," she says quietly.

He lowers his hand. "Where else would I be?"

"With Gina."

He lets her words hang in the air for a moment. He looks down at his wine, rotates the glass and watches the crimson liquid swirl. "You want to know why I'm here and not with her?"

When she doesn't answer, he looks up at her. He can't read the look on her face. He tells her anyway.

"You make everything quiet."

Now he can read the look on her face, because it's pure confusion. He sets his glass down on the counter beside him and holds his hands up on either side of his head.

"There's so much noise in here," he explains. "And everything is always moving so fast. It's fast and it's loud and that's not good if I don't have something quiet too. Something still. Alexis is growing up and soon she'll be gone and Gina…she can't give me that."

"And I can?"

"You already do."

She takes a slow, deep breath. "When traumatic things happen like what happened today, it's a little like being drunk. Everything gets fuzzy and you say and do things you wouldn't normally do."

She's explaining it to him like he's a child. That makes him angry, because she's being guarded. She's letting her defense mechanisms win.

"Maybe that's the problem," he tells her resolutely. Her eyebrows lift a little at his tone. "Maybe the problem is that we don't normally say what we should. Maybe instead of being fuzzy everything is suddenly clear."

She sighs quietly, and points to herself. "Square peg," she says. She prods him in the chest with her index finger. "Round hole."

He captures her finger in his hand. "Is that really what you think?"

"It's what I have to think."

"Why?"

She tugs her finger out of his grasp. "Castle, if we were supposed to be together, don't you think we would be by now?"

"No."

"No?"

"Why does it always have to be immediate? Why does falling in love have to be declarations and ultimatums?" He reaches for her hand, but has to make do with holding it through her sleeve. "Can't two people fall in love without knowing it?"

She doesn't pull her hand from his, and Rick decides that's a good sign. He feels even better when she smiles a little. "They'd have to be pretty stupid."

"Or brilliant," he argues. She arches an eyebrow and he shrugs. "It's like feeling your way around a dark room. You have to get to know everything in a different way than you're used to. But when the lights finally come on, you're ahead of the game."

"You've thought this out," she observes. There's still a hint of a smile on her lips.

He smiles too. "That's not even my best analogy."

"Oh?"

"I think we're the irresistible force paradox too."

She laughs at that. "How?"

"Well, it's the idea that-"

"I know what it is," she interrupts. There isn't any annoyance in her voice. "I just don't know what it has to do with us."

"You're an immovable object," he explains. "You're stubborn as hell. You're indestructible. And me…I'm like a super powered freight train. Irresistible force that just keeps going and going, constantly in motion."

He stops and takes a deep breath. He hadn't realized how worked up he was getting. Beckett eyes him carefully, as if she's evaluating him as much as his words.

"Sooner or later we collide," he tells her quietly.

"Collide?"

"We're on a collision course." He lets go of her hand so he can show her. He makes one of his hands into a fist, and the other into a flat plane, the closest thing to a train he can make. "It's bound to happen. You're here." He holds up the fist. "And I'm coming." He moves the other hand toward the fist. "And we're going to hit head on."

He looks up at her in time to see her lick her lips and swallow. Someday she's going to make him implode.

"And then what?"

"I don't know," he admits. "But I don't think we're supposed to."

"And this right now," she says, gesturing between their bodies, "this is the collision?"

He shakes his head. "No. There's still track between us. There's still unfinished business in other places and growing up to be done."

"Maybe on your end," she teases.

He smiles. "You haven't let me all the way in yet."

Her smile disappears. After staring at the floor for a minute, she shakes her head. "No, I haven't."

She looks so small, and he can't stop thinking about the way she's got her hands pulled inside the sleeves of that huge sweatshirt. She looks up to meet and hold his gaze. He reaches for her slowly, not wanting to scare her because she's as skittish as they come when it comes to sudden physical contact. Her body stiffens visibly, but she doesn't move. He puts a hand on the side of her face, brushing his thumb over her cheek like he's wiping away tears. She tilts her head just barely into his hand, and that's enough permission for him.

He leans forward and kisses her, his lips barely brushing hers. She moves, her hand clutching his wrist as he holds her face. Rick makes no attempt to deepen the kiss, no move to touch any part of her except her face, and she doesn't move either. When he pulls away and opens his eyes, hers are still closed. He watches as they flutter open. When she pulls her bottom lip between her teeth, he smiles. Her hand tightens on his wrist. That propels him forward, brings his lips to her forehead, her cheeks, her eyelids that have fluttered closed again. He presses his cheek to hers, his mouth by her ear.

"You don't always have to be so strong," he whispers in her ear.

She tilts her head closer to his. "You know I do," she murmurs back. Her breath is warm against his ear.

He finally pulls her forward, his arms wrapping around her waist. She grasps the back of his shirt, and he swears he feels a shiver race through her.

"I want to keep you, Kate," he confides, his voice barely audible. "That's what happens after the collision. I keep you. That's why we haven't collided yet, because we both know it'll be for keeps and neither of us is ready."

She moves her head upward and nudges him with her nose. He knows what she wants and finds her lips again. This time he does deepen the kiss, and she kisses him back. Her hands are the ones on his face now, holding him to her even though he has no intention of letting her go.

"Keep me," she whispers against his lips. "Someday."

She kisses him more insistently and something starts building around them, inside of them, and Rick suddenly understands how silence can be deafening, how stillness can move.

And then Kate steps away.

Rick stares at her. She's Kate now, and she's beautiful. She smiles at him, shyly, and his heart turns violently inside of his chest.

"We've got more ground to cover before this," she whispers.

He curls his fingers into fists so he won't reach for her. "Yes."

"We're still in the dark," she says, and Rick thinks he hears a hint of a laugh in her voice.

"Yes," he agrees again. "That was just..."

They smile at each other like teenagers, reveling in the beauty of determined patience despite their new knowledge. "Lightning," she supplies.

He likes her choice of words. "A brief flash. Signaling what's to come."

"The collision."

He makes himself break eye contact, because otherwise he's never going to leave. He nods at his glass on the counter. "Thanks."

"Sure."

He turns away from her, heading toward her front door to let himself out. His hand is on the door handle when she calls his name.

"Rick."

His smile at her use of his first name is involuntary. His conscious thought fractures into a million different trains that are racing in a million different directions. One is headed in the direction of hearing her say his name the way she just did again, the other of her moaning it in bed, one of her saying it softly just after she tells him she's in love with him…

He takes a deep breath, ignores them all, and looks over his shoulder. "Yeah?"

She's standing at the edge of the kitchen. Her arms hang loosely at her sides, her hands still lost in a sea of faded gray fabric.

"The object can't be destroyed. The force can't stop. So the only option is that they both cease to exist. They cancel each other out."

He smiles. "Maybe they only cease to exist separately. Maybe instead of disappearing, they end up existing as one instead of two."

A flash of lightning ignites her eyes, and Rick turns the door handle immediately. He has to get out of her apartment as soon as possible because if he stays and ruins this, ruins them, he'll never forgive himself.

"Good night, Kate."

Her smile is the last thing he sees.