After that day when Castle and Beckett take forever to make it back to the bullpen from the underground garage - their excuse is that the automatic door wouldn't open at first, but somehow nobody else seemed to have encountered that issue - Esposito keeps a close watch on the two of them.
But if they really are dating, they're doing a damn fine job of hiding it. They never arrive at the precinct together; when they do leave at the same time, either they're all going for drinks or Castle and Beckett part in the lobby (Esposito may or may not have been using the precinct security cameras to find out).
And from that moment he starts paying attention for real, it seems all the things he and Ryan have noticed - the looks, the lingering touches - suddenly vanish. Gone in the space of one night.
Esposito's tempted to think break-up, but that's not the vibe he's getting at all. Castle keeps showing up every day, bearing the customary cups of coffee, and Beckett always smiles when she thanks him. And that theory-building thing they've got going - it works better than ever.
It's just... The tension that existed before, the physical electricity that made every cop at the 12th super aware of those two - that's disappeared. They're so comfortable now, so blatantly "just friends," that they have to be sleeping together.
They just have to.
But there's nothing to prove it.
Weeks go by; life happens. One of their arrests ends up with Ryan and the suspect tumbling down a flight of stairs, resulting in a twisted ankle for Kevin and a broken arm for the perp.
Ryan is banished from the precinct for a couple days (Gates manages to make him turn around with her mere glare the one time he tries to show up), and so he doesn't get to witness what Esposito does.
The suspect's wife comes in for an interview the next afternoon; she's young, only twenty-five, with a blond little girl wrapped around her leg.
"My baby-sitter cancelled on me," she apologizes in a murmur, her eyes to the floor.
Of course Castle offers to take care of the child while Beckett and Javier question the shy woman - nothing surprising in that. Esposito sees him from the conference room, spreading blank sheets and colored pens over Beckett's desk (where the hell did he find those?) and making faces for the little girl; honestly, the man's ridiculous.
But the female half of the precinct seems to be falling for it. Beckett included.
It's not obvious at first. His boss is being her usual self, cool and collected, asking clever, precise questions from the young mother, Lila. On a few occasions, she asks for a repeat, but Esposito himself is taking notes, not really paying attention.
At the end of the interview, though, it's become clear that she's distracted. She keeps losing her focus, her gaze straying towards the glass panel that opens onto the bullpen, and Javier is the one to shake Lila's hand, thank her for coming to them.
When he turns to Beckett, his mouth parted on a wry comment, the words never make it out.
She's watching Castle, who's still sitting next to the child, smiling and saying something they can't hear, and her face-
Her face is more open than he's ever seen.
Radiant. Her eyes are bright, something like longing in her parted mouth, and she looks-
She's in love with Castle.
Javier thought he knew that - the whole precinct did, really - so it shouldn't be that much of a surprise. Except. He didn't know a thing, did he?
Looking at her expression now, struck silent by this glowing Kate who might be more amazingly hot now that she's ever been, he sees the truth, the strength of this thing she has with Castle. And he can't say a thing.
He just can't.
In the bullpen, Lila's opened her arms wide for her daughter, and she exchanges a few words with Castle before heading for the elevator. The spell is broken, and when Beckett turns to Esposito, she's a detective again, all business, her face under control.
"What did you make of her?" she asks, and Javier slips back into his own self just as easily, gives her the answer she's waiting for.
But not even the case can make him forget what he's seen.
When they get home that night, Kate's hands are on him the moment Castle closes the door, smooth and urgent and seeking, her eyes dark as she snatches his mouth with hers.
He moans into her mouth, somehow manages to utter the words, "Kate, my mother-"
"Don't you listen?" she murmurs, moving onto his neck now, a little flick of her tongue that has him shivering. "Martha said at breakfast she wouldn't be here tonight."
Shock swallows his answer when he feels the heavy press of her body into his, the heat of her parting thighs, devastating. His eyes slide shut, and he remembers to use his hands, hooks two fingers at her waist, where the skin is so soft.
Whatever he did - whatever it was that got her like this, tight and desperate and nearly climbing up his body, she needs to tell him what it was. He needs to know.
He'll do it every single day.
"Kate-" he pants, hips rising into her eager touch, the thrumming cove of her body.
"Shut up," she orders, ripping - ripping - the top buttons of his shirt open so she can press her lips to his chest, her pelvis endlessly rolling against his. Shit, she feels so good.
He shuts up.
"What did I do?" he hums later, fingers drifting over her warm skin.
The night pours in through his windows, moonbeams catching on Kate's hair, limning the soft, sated smile on her face.
Sometimes he just feels so damn lucky.
She turns her head to kiss the skin above his nipple, a faint caress, the arm she has thrown around his chest squeezing gently, and if he didn't know any better he'd say she's avoiding his question.
"You're just...you," she says evasively, and yeah, he's right.
She doesn't want to answer him.
Hmm. This has got to be good. Is she ashamed?
"I've been me for the past four months," he points out, grinning a little because he can't help it - this is what Kate Beckett does to him. "I don't recall you wanting me so badly that you had to jump me at the door."
Her fingernails dig into his side - probably punishment for calling her wanting - and there's the nip of teeth at his shoulder, entirely too hot considering what they just did, and how thoroughly exhausted he is.
"Maybe I was just better at hiding it," she tells him, her smile brushing at his skin.
He's not buying it. He must have done something; he will harass her until he knows what.
Or he could use the timeline. Use your brain, Castle.
What did he do today that was different from yesterday? He brought her coffee, as per usual, and then they worked on closing that case - caught the killer before they went home. But it's not like that's the first time either. And he wasn't even involved in building the theory that led them to that guy - she did that with Esposito after questioning the young mother-
Kate's nuzzling at his shoulder, rubbing her nose to his skin in that adorable way she only does when she's very tired, about to fall asleep. This might be his chance.
"Does it have to do anything with me watching that little girl?" he asks, his voice very quiet, lips only inches away from her hair.
She sighs, and he feels her smile again, sleepy and beautiful. "Mm, you were adorable," she mumbles, and his heart does that silly little stutter, breath catching in his chest.
She'll never stop surprising him.
"Yeah?" he nudges, can't believe Kate Beckett would actually fall for that old stereotype. The guy who gets along with kids.
"Uh-huh," she says, mouth open at his skin. "She was all shy and quiet, but by the end you had her giggling. And you didn't even care how silly you looked. You just - went out of your way to make her laugh. You have any idea how sexy that is, Castle?"
"Well, clearly I didn't," he chuckles, a little bewildered at the unchecked love in her voice, all that gorgeous tenderness that just spills out of her, wraps around him. "But um, I'll make sure to hang out with kids as often as I can, if this is what I get."
He skims his hand down to the curve of her ass, squeezing a little, and she laughs sleepily, yawns through it.
"You do that," she murmurs, before slipping right into sleep.
He spends the rest of the night dreaming of a little girl with Kate's large green eyes, who runs towards him with her arms open and calls him Daddy.
The morning Ryan comes back to work, the first thing Esposito does is share with his partner what he's seen, and the conclusion he's come to. That's what partners do, right? They share. They work together towards a common goal, coordinate their efforts, all that crap.
So he's slightly disappointed that all he gets for his troubles is to be called a closeted romantic. Ryan smirks at him after his little comment - Aw, Javier, I had no idea you had such a big, sappy heart - and it takes a lot of self-control to keep from actually smacking him.
"You'd believe me if you'd seen her," Esposito mutters, irritated at his partner's incredulity. Frustration gnaws at him and he turns to his desk again, pretends to be absorbed in work.
Stupid of him, because Ryan can't take a hint.
"Look," he insists, grabbing Javier's chair and rolling it back next to his. "I'm not saying I don't believe you. It's just this kind of thing, you know? It's the kind that...you need to see for yourself. Otherwise it's just too crazy. Kinda like - if I was telling you I'd seen a flying pig. You'd never believe me, until you'd witnessed it yourself."
Esposito turns his head slowly, stares at Kevin. "When pigs fly, bro? That's what you're going with?"
Ryan scratches his neck, nearly blushes. "Well-"
The doors of the elevator glide open and both detectives look up to see Beckett and her writing partner step out, cradling coffees and apparently deep in conversation.
"Hey, here comes your mentor," Javier smirks, resting his back against his chair. "A flying pig. Maybe he would like that comparison.
"Hey, I was just trying to make a point-" Ryan starts defensively, but then he shuts up the moment Beckett's eyes land on them, a graceful eyebrow arching.
"Hey guys. What's up?"
"Nothing," they chorus, which of course makes them look completely guilty.
Beckett looks like she's holding back a smile. "Really. Well, you guys are, you know. At the same desk."
"Yeah," Esposito says, trying to sound cool, no big deal. "We were just, uh..."
"Chatting," Kevin pipes in, coming to the rescue. "Just, you know. Morning chat. Nothing that interesting," he finishes with a little wave, Castle-style.
"Aww," Castle joins in, taking a sip of his coffee. "You guys are adorable. Aren't they adorable, Beckett?"
Kate rolls her eyes, clearly not convinced, and goes back to her desk.
"If you were strays, I would totally take you in," the writer adds, sotto voce - like that's supposed to be comforting - before he follows her.
Esposito stares, considers throwing a pen at Rick Castle.
Instead he shakes his head, gives a look to Ryan as he wheels himself back to his desk.
This is not going to be a good day.