Inspired by what happens to my ovaries when NF wears glasses.

Castle mentioned he had a doctor's appointment, so Kate isn't surprised that he walks in later than usual in the morning.

But -

She stares.

"Since when do you wear glasses?"

He shrugs. "The doctor's ordered contacts. I just have these till tomorrow."

"Bro!" Esposito grins, clapping Castle on the shoulder. "You finally decided to show the world you're a loser. Good job."

"Hey there, Four Eyes," Ryan calls from his desk.

"Guys," he waves. "Hi. Thanks."

She bites her lip but finally manages, "Really, Castle?"

He shrugs and opens his mouth, just as the captain's voice rings out. "Mister Castle."

The boys quickly look down at their work while Gates comes tripping out into the bullpen. Castle instinctively stands up straighter and gets a faintly guilty look on his face. Kate tries to hide the smile.

Gates pauses and gives him a slow once-over. "Mr. Castle. This is different."

"Ahh. Yes, Captain." Kate can see his shoulders tense - he's preparing for whatever new thing he's done wrong.

But Gates just gives him one last look, her face set in an odd expression. "Well. It's - different."

There's a long awkward moment, and then Gates abruptly turns and marches back into her office.

Castle looks back at Kate, bewildered.

"Uh. Beckett? What just happened there?"

Kate's relatively certain she knows. She's pretty sure it's exactly the same thing she's thinking herself. She thinks it's the same reason every woman on the fourth floor has been staring at him openly since he walked in.

Kate swallows. He looks good. He looks like a professor. He looks forbidden. She wants to rip everything off him and leave the glasses on. She wants to take him back to his place. She wants him to push her down on his desk. Or maybe back him up against his bookshelves and kneel down in front of him.

She hates him just a little for wearing this blue shirt and brown jacket today, because with the glasses -

She thinks about him in a tweed jacket. Elbow patches. A leather shoulder bag. Pulling out volumes of Dostoyevsky and Flannery O'Connor and Dickens. Grading papers.

The day is a nightmare.

When he starts spinning a story to explain their case, his voice rises and falls in slow, seductive cadences, his eyes so bright behind the lenses she has to cross her legs.

By late afternoon, it's ridiculous. He doesn't even have to talk. At one point he takes off his glasses to polish them, and she has to tell herself not to leap over her desk and straddle him.

He reaches over to hand her coffee, and she stammers a Thank you. The vision crosses her mind, Castle in old-fashioned academic robes, robes she can slide her hand under, get him worked up, make him squirm, make him -

He leans over her desk and pulls a red pen out of her cup. A red pen.

He twirls it between his fingers, his long, strong, nimble fingers -

That's it.

She stands up.

"Castle? Can I talk to you for a second?"

"Uh - sure."

He follows obediently as she leads him, forcing herself not to grab his arm, holding her breath as they pass people.

He seems to think they're heading for the stairs when she glances around furtively, yanks open the door to the storage closet, and shoves him inside hard.

"Beck-what -oof -"

She flips the lock behind her and attacks him, cutting off his wondering with her mouth, finally, finally shutting him up. She can feel those stupid glasses, the frames pressing into her skin, and for some reason it just feels so wrong and she winds her arms around his neck and sucks his tongue into her mouth and just goes.

Castle finally leans in to nip lightly at her jaw as his hands slide under her shirt. He sucks on that spot behind her ear, the one that makes her knees give out. "It's the glasses, isn't it? They really do it for you?" There's a smirk in his voice. She hates him. Because he knows.

"Shut up." He needs to stop talking. She sucks his bottom lip into her mouth and squeezes his ass.

"Kate." He pulls his mouth away from hers with some difficulty. "Kate. You said we couldn't do this."

"Shut up."

"But you specifically said Castle, we are not having sex at the pr-"

She shoves her tongue in his mouth and her hand down his pants. He grunts, his hips jerking into hers uncontrollably, and then he's shoving her back against the wall. She's too far gone, trying to work his pants down, trying to get her own pants off, and they're at work and they can't be doing this -

He turns her around roughly, pressing her hands against the wall, yanking her pants down to her knees, and - and -

She lets out a choked cry as he slides into her from behind and covers her mouth with his hand. He thrusts into her slowly, growling I'm going to be tutoring you privately, Kate into her ear as he rolls his body into hers, long, hard thrusts that have her keening against his fingers. She's already so worked up that it's not going to last much longer. And when his fingers start tracing tight, deliberate little circles over her clit and he murmurs You want an A on that paper, Kate? she breaks apart, shuddering, arching back into him with a long moan caught back in her throat.

When she finally catches her breath, he's still draped over her, panting, his breath hot on her neck.

"You really like these glasses, huh?"

She lets out a short, shaky laugh. "Had a really hot English professor in college."

"Oh." He pulls off her, reaching to tuck himself back in as she tries to wipe herself off. "You didn't - uh - did you - ?"

"No." She presses a soft kiss to his mouth. "But I thought about it a lot."

Kate thinks she's managed to successfully sneak out of the supply closet. She sent Castle ahead of her and waited a respectable amount of time before slipping out. Her hair is reasonably back into place and she thinks her face isn't too red.

And of course she immediately runs into Ryan.

"Beckett, is something going on? Castle's all weird, and he was gone for a while, and -" Ryan stops. Stares. Blinks. "Oh my God. You did not."

"What?"

"Beckett. Seriously. At work?"

"Shut up," she hisses. "It's not -"

"I absolutely don't want to know. Ew. Ew."

Ryan marches off, shuddering. She runs a hand through her hair and hates herself a little bit.

She hates those glasses more.

It's not her fault.

That night she straddles him in his office chair in a little plaid skirt and whispers What do I have to do to pass your class, Professor? into his ear. It's not the first time he's fucked her up against his bookshelves, but it's never ever been this good.

They manage to stumble into his bedroom for round two, and when she finally slumps against his chest, panting, she realizes he's taking the glasses off.

"Remind me to thank my optometrist."

Kate laughs into his skin, running a hand over his sweaty shoulder. "You really should."

"So this is really a thing for you?"

He's half amused, half-curious. She rolls off his chest and stretches against the sheets, letting one hand trace a line over his chest.

"They just -" she shrugs - "they make everything a little sharper."