So... I got this idea of a really baddass Mistress Beckett and came up with this.

Depending on the response it may become a multichapter.

Enjoy and let me know if I should keep this up.

Extremely M, folks. I never wrote enything like this, so... yeah. fingers crossed.

Episode 2x17.

"I am not going to leave you alone!"

"ok, fine. I'm too tired to argue…" And she walks away, suddenly turning back to him "but if I see that doorknob turn, I'll have you know, Mr. Castle, that I sleep with a gun"

"Understood" He says simply, showing his dimples with a smirk.

An hour passes and he was sleep already – so much for a defender – when he hears Kate calling for him. Maybe, just maybe, it was in his dream but a father never sleeps soundly after his child is born, so any muffled cry awakes him. And it did.

First thing he remembers is that she sleeps with a gun and then he hears something heavy being dropped into water, he thinks it might be her bathtub, soon after this weird sound he hears it being taken out of the water and then "goddammit!" her muffled voice again.

He sits on the couch, getting ready to action.

And then a broken glass and another curse.

"Shit!" – and she never curses.

If he was ever considering not bursting into her bedroom he pushes the doubt away. The door is unlocked and he's not at all subtle.

"Kate?" He whispers in caution "you in here?"

"Castle" he hears her calling him from her bathroom.

The door is slightly open and he can see her head rested on the tub's edge facing him. Her eyes are closed and one of her feet's heels are hanging out of the tub. It's not at all too much movement inside the tub, and right beside it there are a shattered glass of wine and his book – he thinks it's Heat Wave – soaked and tossed over the floor.

"Castle – oh god" She calls for him again.

And then he sees.

The water is crystalline with some bubbles around the edges of the tub, but not in the middle, no. He can see her. She's touching herself and it has an immediately effect on him.

Because she's taking a bath moaning his name and his instinct is to burst through that damned door and finger her until he can only feel her muscles clenching with her pulse while her body gives in. But he can't. He's got to see it first.

And what's the harm, really? She's so busy in there she won't even notice, he thought. She's teasing her nipples with her fingers circling her clit and then they slip right in earning a gasp from her "Cas-tle" with a sharp intake of breath.

He knows better. Sure he does. She's probably armed in there. But for knowing better he slides his zipper down. And he would just stick his cock out and touch himself, but he likes it better when he touches his balls, too. So he pops his jeans' button open and lets his pants pool around his ankles. He, then, tugs his boxers down and begins to touch himself.

He cups his balls when she cups her breasts and pumps faster if her fingers pick up the pace. His hand is paying a bit more attention to his head, spreading the pre-cum and – god, it's good – she knows just how to do it.

Her tongue darts out to lick her lips and her eyes roll up in pleasure. Just then he slightly squeezes his balls pressuring his groin with his hands heels and lets out a groan.

Her eyes snap open and she gets up quickly reaching for her gun "What the hell?!" she hisses and he panics trying to flee the scene of his future murder but can't get far with his pants around his ankles. She pulls the bathroom door open, dripping water everywhere and sees the man trying to escape.

He tries to reach for them but she's onto him. His hand is wet from his pre-cum and he can't turn the doorknob so he chooses to face her with his pants down around his ankles and his cock hard and ready to go.

It's really dark in her room and she approaches him, thanking the dark for the cover because she's only wearing the bathtub's water right now. She points the gun to the man and comes closer.

"Castle?!" She barks at him.

"Beckett. Hi" He shoots his hands up and backs up against her bedroom door.

She comes even closer to make sure it's him and bumps on his cock between them.

"What the-"

"Don't shoot me" He pleas.

She gropes down and feels him with her left hand. She grabs him and he lets out this whimper, almost coming.

There's nothing she could've said, really. She's stroking him in the dark by accident.

"Wha-" she sighs and gropes for the light switch. Her dresser is just next to it and she puts her gun in the top drawer, unloading it as she puts it away. "Were you watching me?" She finally asks but she doesn't let him go.

"I heard a strange sound" he pants "and then shattered glass" please, don't kill me he meant to say.

"What?!"

"I came to se-" He sighs "I came to check on you"

"Were you watching me, Castle?!"

"You di-didn't answer, so I-I-I" He closes his eyes and hopes for the best.

Hopes she'll make it quick and painless.

She presses her body into his and squeezes his cock.

"Oh – dear god – you're nak-" his voice trails off as she pumps him hard at the base and gently by the head.

"Take it off" she hisses tugging at his shirt.

He immediately obliges her wish, but doesn't reach for her.

He hears her cuffs and he's sure she's gonna arrest him in his birth suit to make a point.

"Turn around" She lets him go and roughly pushes his front to the door. The cuffs are cold around his wrists on his back and she's still pressing her body into his.

She then switches the lights on. "So, you were watching me" she drags her voice on every word. "And I'm gonna teach you a lesson, Castle. And you better not forget it"

"Kate, please" He grunts and he hears her gun again.

Her gun roams his spine down, the cold metal against his skin makes him shiver and it's half fear, half lust.

"I'm feeling a sort of déjà vu here… don't you?"

He gulps his fear down "I don't know what you mean"

"Oh, really? You write about me wrestling a bad guy naked, soaked from a bubble bath and-" the gun slides around him and it is shoved under his cock, pressing his balls.

His hips jerk up to the movement and her sultry voice by his ear.

"Bu-but I'm not a bad guy."

"I thought bad guys were the ones who did bad things, Castle."

"y-Yes"

"And it's not a good thing to spy on me, Mr. Castle. Never"

"Just because it's no-not good, doesn't mean it-it's bad"

"True that" She lets out an evil laugh and his hips twitches.

She's holding the gun and his cock pressed together, stroking him with the cold metal, heavy against his soft skin.

"But you know what you did that was pretty bad?" she turns him around to face her.

"N-n-no, no" he gulps down again not able to restrain his hips' jerk.

"You got in the way" Her tone is serious, her eyes on fire.

She presses the gun hard on him, making his eyes roll up in pleasure.

"Get down on your knees" She orders sharply.

His legs are shaking badly but he manages to do it.

She presses the gun to his head and slides it across his jaw "such a pretty face…"

"Ru-ruggedly handsome" he hisses.

The gun slides down over his throat and rests on his chest.

One of her legs comes up and rests on his shoulder and he looks to his side to see what's that about but his cheek hits the gun. "Face forward, Castle." She barks.

Something smells dark, forbidden. It's heavy, even darker and god, he wants it.

"Suck me, Castle" She hisses and pushes the gun on the back of his head forcing him forward until his lips are on her.

please notice that the gun is unloaded.