Castle's been back at the precinct for a week and a half when he gets his first chance to make a dent in Kate's wall. They're working a double homicide – a recently married couple, Jason and Lisa Herdman, have been found dead in their bedroom. The husband was pinned to the wall in a ghastly parody of the Christ figure, while his wife lay on their bed, naked, stabbed in the abdomen.

The whole room was spattered with blood, the rich red color clashing with the pale pink of the wallpaper. The gruesome spectacle had left them all uneasy – not even Esposito's joke (that if this was a serial killer fixating on newlyweds, it was lucky Ryan and Jenny were not yet married) had gotten more than meagre smiles out of them.

After two days of investigation, they're short on leads and short on suspects. They're double-checking alibis (well, Castle is staring at Kate while she double-checks alibis) when Ryan hangs up and hums interestedly, writing something down. Castle, along with the others, turns a questioning eye to the young detective. Kevin only smiles, looking pleased with himself, and taps his chin with the pen he's holding.

"Ryan."

Kate's voice is rough with frustration and impatience. Castle looks at her mug: empty. It seems coffee is very much needed; he'll go get some, as soon as Esposito's partner tells them whatever put that cat-ate-canary look on his face.

"Well," Ryan starts, taking his sweet time, "I was calling the Byrne Theatre to check Reverend Daniel's alibi."

It takes half a second for Castle to remember who Reverend Daniel is. Right, the guy who married Jason and Lisa.

"And it seems," Jenny's fiancé goes on with a small, slightly irritating smile, "that there's a small problem here."

"We checked," Esposito objects. "He still had the ticket for the play."

"Yes, but. Whoever we talked to last time forgot to mention something pretty important."

"Which was?" Castle prompts, because he can tell Kate is fuming next to him.

Satisfaction is almost rolling off Ryan when he delivers his next line. "There was no show that night. The play was cancelled."

"What? Why?" Beckett inquires firmly, a mask of concentration falling over her beautiful face.

"Their lead was sick, and the understudy didn't show. They had to cancel."

"So," Castle thinks aloud, "Daniel bought a ticket to use as his alibi, but he didn't go. Which is why he didn't know the play had been cancelled."

"And even better," Ryan adds. "The theatre called or emailed everyone on their list, offering either a refund or a ticket to another show. Daniel didn't send his ticket back.

"He wanted to hold on to it," Kate realizes, the annoyance completely gone now. She sounds thrilled, almost triumphant. "He *needed* it, for his alibi."

"Am I the only one," Esposito intervenes, "who finds it hard to believe that a church guy is responsible for that murder scene?"

Castle shrugs, though he can see Javier's point.

"Even reverends can be rotten inside, Esposito," Kate answers with a grim look. "Okay. You two go pick up the guy, and we'll go through the evidence and the crime scene photos again, see if we can link him to this."

The writer watches the guys leave, then jumps to his feet and snatches Kate's cup. She shoots him a grateful, warm glance that leaves his knees a little weak. He tries to tell himself that she's just pleased with the progress on the case.

Still. As he heads for the break room, he realizes what exactly caused his breath to catch in his chest, what's responsible for that strange leap of his heart.

She's being so completely open. She's not hiding her feelings from him anymore. That look in her dark eyes – she's letting him in. The thought shakes him to the core, sends excited delight tingling into his toes and fingertips.

Kate Beckett, letting him in.

He's not so sure he will need that plan of his, after all.

They haven't found any way to incriminate the reverend when Ryan and Esposito come back empty-handed, stepping out of the elevator alone. Castle watches Kate's brow furrow, the way her jaw sets. So beautiful.

"You didn't find him?" She asks as Esposito sinks dejectedly into his chair, Ryan sitting on the edge of his desk.

"Oh, we did," Kevin answers, irony lacing with his words. "But once he understood the goal of our questions, the good reverend got…irate. Absolutely refused to follow us. And he had a few believers there who jumped to his defence, started vouching for him. You'd have thought we were Satan himself. Also, our friend Esposito had some crisis of conscience and didn't exactly help –"

"Dude, I don't remember you fighting to take this guy away," his partner snaps.

"Well it's not like I could've done it on my own when my partner was –"

"Guys," Kate calls decidedly.

They go quiet in an instant, and Castle smirks. He loves it when she exerts her power.

"Did he at least answer your questions?" she asks, arching an eyebrow.

"Before he realized we were suspecting him, yeah," Esposito answers, looking a little sheepish. "Says he didn't know the show was cancelled because he was sick, stayed at home. No one can verify that. When we asked why he had lied, he got pretty angry, said he had just confused the days, that he had gone to the theatre several times that week."

"Is that true?"

Ryan shrugs. "One of the girls from the theatre remembers seeing him there last week. Or so she thinks. They don't have security cameras, so we can't be sure, one way or the other."

"Hmm." Kate's lower lip has been sucked in between her teeth; Castle watches with a mixture of arousal and concern for the fate of that poor, worried lip.

"Did you find anything that could point to Reverend Daniel?" Ryan asks, his eyes traveling over the murder board.

"No," Castle admits. "Well, except for Jason being pinned up to that cross."

"And that's thin," Kate adds somberly. "Not the kind of detail you can build an investigation on."

"What are you saying?" Rick turns to her, surprised. "You don't think he's our guy?"

"It's not about what I think, Castle. It's about what the jury will think. You know that. We can send uniforms to pick up Daniel, and we can question him, but if he doesn't crack… We've got nothing against him. I don't even know how we'll convince a judge to let us search his office or his home."

"Well," Castle says. "There's always the Lois and Clark method."

Kate's large, bottomless eyes fixate on him, alive with curiosity, and his chest tightens.

"I mean, you and I could go there, pretend to be an engaged couple looking for a minister, and I'll find a way to distract him while you search his office."

"Undercover."

"Yeah."

"Gates is not going to like it."

"Nope."

A sly smile stretches Kate's lips. Castle can feel Ryan and Esposito smirking, even though he can't see them; but it doesn't matter because Kate's studying him, considering his suggestion, and of course he knows they wouldn't *really* be engaged, but still. The idea shimmers appealingly in his mind.

"What if he knows you?" She says at last.

Castle raises a shoulder in a half-shrug. "I can pretend I'm flying under the radar because I don't want the press to learn about my new love interest and impending wedding."

He thinks she just shivered. It's impossible to be certain, of course, but… He thinks her spine straightened when he said wedding.

How interesting.

After a minute, Kate nods slowly, still deep in thought. "All right, Castle. We'll do it your way. Give it a try."

He has to wrestle back the instant, blinding, overwhelming joy – you'd think she'd actually agreed to marry him.

"In that case," he says, forcing his voice into a low, nonchalant tone. "Do I get to buy you a ring?"

Kate smiles – actually smiles, wide, dazzling – before she drops her eyes to her desk, as if afraid that she's showing too much.

"I'll be fine using my mother's ring, Castle. But thanks for offering."

Are those the faintest traces of a blush on her cheeks? The looks on Esposito's and Ryan's faces – somewhere between agape and mightily interested – seem to confirm it.

A whole world of possibilities opens before him. He cannot help losing himself, cannot keep his mind from wandering. Kate Beckett smiling when he jokes about buying her a ring? It seems insane, much too good to be true.

Maybe this is an alternate reality.

When he emerges from this dreamland made of engagement rings, wedding dresses and Kate Beckett, his partner is standing at the door of the bullpen, her jacket thrown over her shoulder, amusement etched on the harmonious lines of her face.

"Are you coming, or what?"

"Yeah, yeah," he hastens to reply, trying not to trip over his own feet as he passes a snickering Esposito and a knowingly smiling Ryan.

He's always had a thing for alternate realities, anyway.

The reverend is a man in his forties, clean-shaven, with deep brown eyes in a rather heavily lined face. He doesn't look all that threatening, Kate thinks as she sits down in his office, acutely aware of Castle's fingers entangled with hers.

He insisted, when they were in the car, that they should really look like a couple, so that Daniel wouldn't get suspicious. Kate agreed, but she didn't miss the elated glimmer in the writer's eyes. He's going to try and make the most of this. Well, she can always choose to turn the tables on him, whenever she feels like it.

For now, the reverend is asking them basic questions, how they met, their concept of religion, the way they envision their wedding. Castle is doing a wonderful job of answering these, and she's letting him talk, using the time to detail Daniel's office.

She quickly spots the cabinet where he seems to be keeping his files. That's her target. She's trying to think of an excuse to get up and look around when Castle addresses her.

"Right, honey?" He asks with a tender smile.

Honey? Oh, he will pay for this. Kate tries to breathe past the lump in her throat, direct result of the expression on his face. If Castle is playing a role, then he's an even better actor than his mother.

Who is she kidding? She knows he's not playing.

"Of course," she answers at last, finding a smile for him when he squeezes her hand in warning. "Yes."

The reverend is giving her a strange look, so Kate acts on instinct. Leaning in, she brushes Castle's lips with hers, and presses a kiss to his cheek. She feels him freeze against her; she lingers, giving him time to regroup, to remember why they're here.

When he relaxes slowly, she lets go, sits back straight in her chair.

God, this whole thing is a *terrible* idea. Why did she let him talk her into it?

But her little manoeuvre worked. Nicholas Daniel is looking at them with kind eyes now, obviously thinking something along the lines of aren't they cute. She finishes the job.

"It was love at first sight," she explains with a shy, sheepish smile. She tries not to look at Castle.

The reverend seems to be eating it up.

"So, uh," her 'fiancé' says, clearing his throat. "Could we look around, see what the church is like? We don't want something too big, but we do need some space, with the guests and…"

He doesn't finish his sentence, but Daniel has jumped up, a commercial smile on his face. Huh. He no longer looks like the fatherly, warm man from the beginning. Kate makes a note of that.

Castle extends a hand to help her on her feet – she doesn't know whether to be annoyed or amused at his gentlemanly ways – and she raises gracefully…Before falling back down with a yelp of pain.

Her acting skills are rather good as well, if the concerned expressions on both writer's and reverend's faces are anything to go by.

"Oh," she moans, circling her ankle with her hands and trying to massage it.

"Kate? Are you alright?"

She can tell by his voice that he's figured it out – moaning is not really her style. But Nicholas Daniel doesn't know that.

"Are you hurt, my dear?" the older man inquires with solicitude.

"Oh, it's just… I twisted my ankle when I got out of the car earlier. I thought it was nothing, but obviously –" She bites her lip, like she doesn't know what to do. "It's not that painful," she says hesitantly, "But maybe it'd be better if you went to the church without me? I can wait here, I don't mind. You'll have to make a detailed account for me, Rick," she adds playfully, giving him a soft, teasing look.

She can see his Adam's apple move as he swallows heavily. Ha. Take that, Castle.

"Are you quite sure?" the reverend asks. "I could call one of my aides to keep you company, if you want? Or maybe check if we have a wheelchair –"

"Oh, no, really, don't trouble yourself on my account. I'll wait here patiently. I trust Rick's eye," she finishes with a smile.

That part is, well, sort of true.

"Oh. Ok, then." Daniel is twisting his hands, and Kate gets the feeling that he's not really pleased with this development, but that he doesn't know how to help it. "Well, we won't be long. Make yourself comfortable."

"Thank you," she answers, doing her best to look both charming and harmless.

"I'll see you soon, love," Castle adds, and before she can even digest the moniker, he leans in to kiss her, his lips meeting hers in a gentle, but firm way. They're warm, and soft, and Kate wants nothing more than to dart her tongue into his mouth.

Oh, god. Terrible, terrible idea.

She's grateful that Castle lets go quickly, grateful to be left alone with her pounding heart, her buzzing ears. But she still catches the pleased look on her partner's face as he walks out after the reverend.

Bastard.

Terrible, wonderful, terrible idea.

Castle's so preoccupied with thinking about how good her lips felt under his that he barely realizes the Reverend has stopped suddenly in front of him. He bumps into the man and totters for a moment, his hand out to touch the wall for balance.

The offices are connected to the sanctuary via a long hallway, probably a former open-air walkway that was enclosed when the church remodeled. Castle can clearly see all the way back down the walk to the hallway they've just left, and ahead of him, he can see the double doors leading to the church.

"Reverend?"

"Oh, I've forgotten it. I'm so sorry. I can't believe-"

And he's already started to rush back the way they've come.

Panic seizes Castle - Kate's back there rifling through the man's private files (which is so illegal) - and here comes Reverend Daniel, hurrying like he knows exactly what's going on. Castle lunges after him, snatching at the man's dress shirt, hoping to stop him.

Daniel does stop, and he glances back with an odd expression.

Castle stumbles on a plausible excuse. "What is it? I'm sure, since we're already so close, we can just go on and see the church-?"

"I've got a great brochure, though, which lists all the amenities, the wedding services - you know, like, extra chairs, a welcome table or podium, a tablecloth - the things you can rent from us to make it easier for the set-up. It also lists the times we're open, so you can come in and - Really, I must go get the brochure."

And just like that, Daniel is rushing back.

Castle jerks forward, scrambling for an idea, something to warn Kate, a way to get this guy going somewhere else, when an older man in a baseball cap turns down the walkway and stops the Reverend.

"Oh, good, there you are. Look, Rev, we've found where we think the rats are getting in."

Reverend Daniel's face blanches and he casts a hesitant look up to Castle. For his part, Rick tries to look appropriately concerned, seeing as how he and his fiancé are looking to rent the sanctuary for their wedding, and steps closer to the maintenance worker.

"Rats?" Castle says, egging it on.

Daniel takes him by the arm and shakes his head. "We are definitely on top of the problem. No, not even a problem, let me assure you. If you could possibly. . .if it isn't any trouble, do you mind waiting in my office while I see. . .?"

"Oh, naturally," Castle responds, nodding his head. "I definitely think you should check out this. . .rat. . .situation."

Daniel practically slumps with relief. "If you'll just wait in my office with your lovely fiancé, I'll be back in a jiffy."

Castle smiles and nods, heads straight for Daniel's office as the man scuttles away with the maintenance worker. The second the two are around the bend in the opposite direction, Castle bursts inside.

Kate jumps and goes for her gun, like an instinct maybe, but Castle holds his hands up and shakes his head. "Sweetheart, you were nearly made. Daniel was rushing back here to get some brochure and then a maintenance worker, thank God and pun intended, diverted him."

Kate's got her hands in the files from the Reverend's little cabinet next to his desk. She gestures with the folder and cuts her eyes to the door. Castle closes it behind him and heads over to her.

"Our victims' file. See this?"

Her finger is on the section labeled: Vices. It's odd, because the Reverend hadn't asked them for particular sins, or even if they have recurring arguments, and it's not like the revered was offering marriage counseling.

"Vices?"

"He's got notes here, but I can't figure out what they could mean. I want to take this back with me, but-"

"Wait. Here, let me take pictures with my phone," he interrupts, digging his phone out of his pocket.

He pulls up the app and fiddles with the screen to make it zoom, then clicks a few. Too late, he realizes they went straight to instagram and he curses under his breath. "Oh crap. Kate-"

At that moment, he hears Daniel outside the door: "I've got those heavy duty nails in my office, Charlie. Let me get them-"

Oh, shit. (Wait, he has nails?)

Kate, apparently not as distracted by that revelation, slaps the file shut on his fingers and shoves it back down into the hanging folder. The doorknob twists open. Castle pockets his phone, but just as he's moving, Kate grabs him by the lapels and shoves him into the filing cabinet.

The force of his back against the open drawer closes it, and the sound of his body against metal muffles the thump of the drawer closing.

And if that wasn't enough, Kate's body is pressed against his, and she's launching herself at him in an attempt to make it all seem less conspicuous.

He catches her with his mouth, her lips dry and chapped at first, but softening the longer he kisses her. She moves her head like she's going to pull away, but he captures her with his palms, brings her in to feast on her. His tongue darts to the sweet spot at the corner of her mouth and swipes along her lower lip, even as she takes it, almost passive against him.

When he sucks on her lower lip, she moans and her knees slide against his, her hands finding his chest. And then she gives back, exploring his mouth with a hot intensity that stuns him, leaves him vulnerable to the dirty way her tongue moves.

Her body seems to rise towards his even as she assaults him, sliding her hand into the placket of his dress shirt, her cool, strong fingers meeting the cotton of his undershirt, her thumb fiddling with a button as if she might pop it open.

Dazed, but not at all stupid, Castle takes that as permission. He moves a hand to her back, rucking up her shirt under her blazer, higher, to her bra, sliding his fingers under it. He curves a palm on her ass and lifts her just slightly higher-

"What do you think you're doing? In my office? This is highly inappropriate."

The reverend's voice hits him like a slap. Castle pops his lips off of hers and blinks past her gorgeous, flushed face to the Reverend standing, gob-smacked, just inside his office.

Castle looks back to Kate (because the sight is just oh, so much more appealing, with her hair mussed from his hands and her lips tinged red and her mouth open, panting). But then Kate pulls it together and jerks back from him.

"We have certain standards of behavior, walls in place to keep us from crossing certain lines-" the Reverend starts, but Castle can't take his eyes off of Kate Beckett.

Yeah. They have walls as well, he thinks. And they've just pretty much knocked down all of them.

Haven't they?

He's got to talk to her about this before she can start rebuilding that wall.

Kate follows Castle out, still too stunned to do much more than stare and try to keep her mouth shut. That kiss – oh, god. The undercover one was nothing compared to this. All she wants is to grab Castle, push him into a wall in a deserted alley, and finish what they've started.

It scares her, how fast, how much she wants that.

She pushes it back firmly, the devouring hunger, the siren song of her skin calling for his. It unbalances her, makes her lose her focus. When she lifts her eyes to look at Castle, he's watching her with a strange expression, somewhere between pleased and unsure.

"What?" She says, and crap, her voice is too low, too needy. So not her.

He smiles, wide, like he can't help it.

"I was only *surprised*, Castle," she snaps, while knowing perfectly well that trying to justify herself isn't going to help matters any.

"Oh, is that what you call it?" he answers teasingly, knowingly. Damn, she won't be able to make it out of this with her dignity intact. "Because that felt more like *enthusiastic* to me."

She bites her lip, lowers her gaze to the pavement. Anything, anything but his handsome face and laughing eyes will do.

"Don't you remember what I told you, Castle? That day at the swingset? About the wall?" She asks finally, because she can think of no other way out.

He grows more serious, but his eyes are still that intense blue and –

No, not going there.

"I do," he answers, determined. "But Kate, I think you're wrong."

What the –?

"What do you mean, wrong?" She exclaims, suddenly indignant. She's trying her best here, trying to be better, to eventually be what he deserves, and he just told her this is *wrong*? "Because what, Castle, you know me better than I know myself?"

"No, no," he hedges, his hands half raised as if to appease her. "I just mean…I think you're confused, Kate."

Ha. Well. He's got that right. She arches an eyebrow, letting him know she'll hear what he wants to say. Castle draws closer, which makes her nervous. Still, she doesn't step back.

She's not sure why.

"I think… That wall inside. It's here because of your mother's death, because the pain was so great that you never wanted to hurt like that again. You told me that. So this… This has to do with loss. Grief. Not with vengeance, not with murderers running around or an unsolved case. Those things aren't connected. You want to solve the case because it's who you are, because you crave justice, and your mom deserves it. But vengeance isn't gonna fill the hole she left in you."

"And what is, Castle?" She asks challengingly, working her jaw. "Love?"

She regrets it the moment the word tumbles out of her mouth. Not because of her cynical tone, not because of the hurt that flickers in Castle's eyes, but because it slices right through her – the realization that it might be true.

That he might be right.

They stare at each other, the weight of all those unsaid words hanging between them (well, if she's honest, some of them have been said, she's just pretending she doesn't remember). The writer looks into her, and he must see too much, because he takes one more step forward.

Her defenses are down, and she's vulnerable, open in a way she's never been with anyone. Could he be right? Can the wall have nothing to do with solving the case?

It's a terrifying thought: if it's true, she's been pushing Castle away for nothing, she's put him through that lonely summer for no reason.

No, that's not true. She needed that time alone, needed to figure out what it was she really wanted.

And she knows, doesn't she? She wants him.

What if there's nothing standing between her and what she wants?

She's dangerously leaning forward when her phone saves her, shrilling loudly and making both of them jump. She takes it out of her pocket – her hand is trembling slightly.

God, the things that man does to her.

It's Esposito calling. Kate mentally blesses her old partner, tells Castle it's the precinct, and takes the call, starting her way back to the car.

The five minutes' walk to get there isn't long enough for her to forget the disappointment etched on Castle's face, the gentle shadows thrown there by resignation. She can taste blood in her mouth as she settles behind the wheel, an indication of how lame she feels; and she's left with that one, terrible piece of knowledge.

She's a coward.