Disclaimer: The only part of Castle that I own is the TV on which I watch the show.

Castle had kissed, more than kissed, her goodbye half an hour ago, and should be on the train to Washington by now. Beckett's alone in his kitchen, perched on a stool and having another cup of coffee while she reads the paper. Wearing one of his tee shirts—the STUD MUFFIN one she'd bought him as a joke a few weeks ago—she's able to relax this morning because she has a court appearance and doesn't need to leave until almost 10:00. She's in the middle of a movie review when she hears his key in the lock, and she jumps up and smiles, one hand on her hip, and puts on her sultriest voice.

"Forget something, Castle? Or did you already miss me?"

"Detective Beckett?"

"Alexis?" Oh, shit. She tugs on the hem of the shirt, but it still barely covers what she really, really doesn't want Castle's 18-year-old daughter to see.

"Aren't you supposed to be at work?" The girl is even paler than usual, which seems almost impossible. "I mean, aren't you usually there much earlier than this? And Dad?"

How can she get from the kitchen to the bedroom in her deshabille without walking by Alexis? Oh, she loves the French. Deshabille sounds so much better than "almost naked," since the only thing she has on under Castle's tee shirt is her own skin. "Your father's on his way to a mystery writers' conference in Washington and I'm going to a parole hearing later this morning so I had, um, extra time." She coughs. "How's school?"

"Fine."

Amazing how a benign four-letter-word can sound so chilly. "Good, good. I'm glad. Sorry you missed your Dad."

"I'm not here to see him." She's still standing ten feet in front of the door. "I just came to pick up a couple of things."

"Okay. Well, its nice to see you. I'll be out of your hair in a couple of minutes. Just have to shower—get dressed." And with that she flees the room. She shuts the bathroom door, leans against it, and sighs. She wishes that she and Alexis could get closer, wishes that Castle had told her about them sooner, wishes a lot of things. All right, she's mortified, and she's not staying here. She'll pull on what she wore yesterday, which is currently strewn around the bedroom, and go home. She can bathe and change there. Ugh.

A few minutes later she walks into the living room, but there's no sign of the newly-minted college student. "Alexis? I'm going now. Bye!"

A faint "bye" comes from somewhere upstairs.

Alexis waits to hear the click of the front door before she comes downstairs with the jacket she'd collected from her room. She shudders at the memory of her encounter, or whatever it was, with Beckett. It's not as though she doesn't know that the detective and her father have sex, it's just. Just, does she have to flaunt it? Sitting there in his shirt? God. When he's not even here! And she's going to break his heart, or worse. Dammit.

Munching on an apple before she leaves, she remembers that she's out of stamps. No problem: her Dad always has sheets and sheets of them in his desk drawer. He's a sucker for almost every commemorative that's issued: dogs, flags, old movie stars, lighthouses, trees, historical monuments. She drops the apple core in the garbage disposal and heads for his office. She misses it, misses watching him write and spin in his chair. She may be 18, but she still likes to spin in his chair; hell, he's in his 40s and still likes to spin in his chair. When she was little she used to close her eyes and make bets: how many pencils were in his pencil holder? When she opened her eyes, what's the first book she'd see? Was the wastebasket empty or not? She sits down, as she's done for years, and takes a few whirls; when she stops, her eyes light on an open, leather-bound notebook on the desk. The left-hand page is covered in his handwriting and the right is already a quarter full. It must be notes for his new book. She hasn't seen any of those in a while, and this will be fun, like old times.

But it's not notes for a book. It's a journal. It's personal. She realizes it the instant she picks it up and the name Kate emerges from a sea of ink. A morass. Quicksand, sucking her in. She knows she shouldn't read it, but she does. When she's halfway down the page, three sentences sear her retina; at least, that's what it feels like.

I never thought it was possible to love someone the way I love Kate. Everything. It's everything.

Oh, God. She's going to be sick. She has to get out of here. She runs through the loft, out the door, and down the stairs. At the third-floor landing she stops, bends over to get some air, and sits down, still gripping the bannister. Kate is everything? Everything? What about her? His daughter? Isn't she anything? She doesn't want to cry, but she does, stifling the sound with her jacket. When she's done, she stands stiffly, walks down the stairs, through the lobby, out the door, and onto the street, where she follows the route to the subway by rote. Because she doesn't feel a thing.

It's been sixteen days. More than two weeks since Beckett has seen, spoken to, or had any communication with Alexis. More than two weeks since their kitchen moment. That's not unexpected, really: it had been awkward, and she'd never mentioned it to Castle. Safe bet that Alexis hadn't either. But Castle is another story: he's fretting, way more than he'll acknowledge. He's seen his daughter only once over that stretch, when he he'd taken her out to lunch, and she begs off or keeps the conversation short whenever he wants to FaceTime or Skype. In sixteen days, he's been the only one to initiate contact. But he'd promised not to poke around in her life too much, now that she's 18 and living on her own, and he's trying not to pry.

"Darling," Martha had said last night when her son hadn't been able to hide how morose he was about how seldom he sees or talks to Alexis. "She's in college, for Heaven's sake. She's spreading her wings. Birds do leave the nest, you know. But she'll come back."

"Well, you certainly did, Mother," he'd replied.

"Now, now."

He's been distracted all day. No one else has noticed it, but she has: the slight shifts in body language—he's curling in on himself a little—the just-detectable faraway look in his eyes. She's grateful that the case they'd wrapped up today was a straightforward one that didn't require his unique kind of theorizing. He'd even begged off around 2:00, with the excuse of having to write. "You know me, guys," he'd said chirpily. "I'll take writing over paperwork any day." But as she'd watched him go to the elevator she'd seen his shoulders slump and she'd known exactly what he'd do at home, especially with no one there to see him. It would be moping, not writing.

"You're a Detective. Detect," she scolds her reflection in the precinct ladies' room mirror. Alexis's coolness started right after she'd found Kate alone in the kitchen, in Castle's shirt. He'd hardly been a monk before he'd met her, but he'd told her that he'd always been very careful about having the women he was dating spend time in the loft. That has not been the case with her. She all but lives there now, much as that surprises her. Right after she and Castle got together, Alexis went to Europe with her grandmother; after she got back, she spent the rest of the summer in the Hamptons. The last week in August she moved into the dorm at Columbia. Still, until recently Alexis had been in and out of the loft often and seen her there; she wasn't warm, but she wasn't rude or unwelcoming. So what had happened? It's beyond unlikely that Castle had done something to upset his daughter to this extent, so she must be the guilty party. But why? What has she done?

It's the end of the day. She takes one more perplexed look in the mirror, goes back to her desk, and tries to decide how to approach Alexis. Something has gone awry and whatever it is, she wants, needs, to clear the air. She can't call her, can't text or email, because it will get her nowhere. If Alexis ducks her father, she's sure to do the same with her father's girlfriend. That leaves one route: she'll go see her. Ask her straight out. Castle has told her stories about what a serious student Alexis has always been, the kind of kid who did her weekend homework by dinnertime on Friday while everyone else waited until Sunday night. Kate doubts that she's changed: it may be late Friday afternoon, and she may be in college now, but Alexis will be studying. She grabs her bag and her coat, says goodnight to Espo and Ryan, and leaves. As soon as she's in her car she takes out her phone and texts Castle.

Lanie suddenly free so we're having a drink. Later. xox

She hates lying to him, but it's forgivable. It's in the best possible cause, and he never needs to find out. She tucks the phone away and pulls away from the curb: next stop, West 112th Street. Alexis's dorm.

Traffic is horrible. What was she thinking? She should have taken the subway. All the way stopping-and-starting uptown she goes over her side of the conversation. The closer she gets to Columbia, the more she wonders about the wisdom of her choice. What if Alexis is in the library? Somewhere with a study group? Drowning her sorrows courtesy of a fake ID? Scratch the last one. Never.

She finds a parking place a block away and stops at the nearest Starbucks for the chai that Alexis likes and an industrial-strength coffee for herself. She adds a slice of lemon pound cake as some kind of peace offering, inhales deeply, and walks to the dorm. Help me, Lord, she says silently.

A student is coming out of the building, so she doesn't have to buzz Alexis to get entry. It's a bit of luck, as she wants the element of surprise. She walks rather than rides to the fifth floor, and knocks on the door. She'd expected a "Who's there?" but instead hears the doorknob turn and sees Castle's daughter in sweatpants, slippers, and a jersey, her hair in a braid.

"Detective Beckett?"

The girl is clearly shocked. Beckett smiles and holds up the little cardboard tray. "May I come in? I'd love to talk for a few minutes."

"Oh. Okay. Sure. Sorry. Come in. I'm studying. Pre-med is already a ton of work."

"Your room's so nice. Just like your father told me." Oh, shit, why had she said that? She rushes on. "I love the round window. You're incredibly lucky to have scored a single as a freshman."

"Right."

"Here. This chai is for you. And the cake." Where is she going to sit?

"Thanks. Uh, why don't you take my chair?" She gestures towards her desk. "I'll sit on the bed."

The dead air around them is suffocating. Should she wait for Alexis to ask her why she's here, or get the ball rolling herself? Alexis is looking at her lap and picking nervously at the plastic wrap around the cake, which answers the unspoken question. Suck it up, she tells herself. You're the alleged adult here. "I'm sure you're wondering what I'm doing here. If you want to kick me out and tell me to mind my own business, I'll understand, but I hope you won't."

No response.

"Oh, and please, call me Kate. I'd really like that."

No response.

"Or Beckett, if you'd rather. I answer to that, too."

No response.

She takes a gulp of coffee. It may not do anything for her nerves, but it gives her resolve. "I'm just going to jump right in, Alexis. I think I must have done something to upset you, in some terrible, enormous way, and I don't know what it is. I apologize. It's just," she pauses to brace herself for the next part. "It's just that I feel as though you're punishing your Dad for something that I've done. He doesn't talk about it, but I can see how your—" Your what? "Your absence, is eating him up. And it breaks my heart." Unconsciously she puts two fingers on the spot where a sniper's bullet had torn her apart 18 months ago. "I've never seen a father and daughter as close as you two."

Alexis still hasn't said anything, but at least she has her attention. She can see it in her eyes and the straightening of her spine.

"I can tell how upset you are, too, even though I don't know you well. It must be hard to accept a girlfriend in your father's life."

Those pale blue eyes are ice. "My father's had a string of girlfriends."

Jesus, thanks for the reminder. "Right. Yes. It's. Well, even at my age if my father started dating someone I'd have a hard time with it at first."

"Our situations are totally different."

"Yes, of course. Yes, they are. You're only eighteen."

"That's not what I mean. Your mother loved you."

Of all the things that might have come from Alexis's mouth, that was one she'd never have considered, and it almost brings her to her knees. She gathers herself again, looks right at the girl.

"She did. Yours does, too."

"In her way. But I've never been her top priority. Most of the time I'm not even in the top ten."

"Oh, that can't be true." If Meredith were in the room she'd smack her so hard she'd land on her siliconed ass in the middle of Broadway.

"It is. I've accepted it. But I've always known that I'm number one in my father's life."

She puts her hand out, but she's too far away to touch Alexis. "Of course you are."

"Not any more."

TBC

A/N This came from a prompt from Roadrunnerz, but it's a little too early in the story for me to reveal it.