Disclaimer: Don't own it, don't profit from it.

A/N: Shameless smut, written for the prompt "phone sex".

The sound of a pistol hitting the cold cement floor echoed through the warehouse as a single tear crept down Nikki's cheek -

The fingers that had been running across the keyboard stopped dead on their tracks. A single tear? Who actually cries like that?

Castle leaned back in his office chair and stared at the laptop's bright screen. Only a few lines of text decorated the blank page that was supposed to be chapter number twenty of 'In Heat', his newest Nikki Heat novel. The deadline was closing in at an alarming rate and as much as he didn't want Gina to twist his pancreas into a balloon animal, he just couldn't concentrate.

Running a hand through his unruly hair, Castle pressed a single key and the image of a green table and a scantily dressed woman appeared on the screen. Online poker was nothing compared to the excitement that sitting face to face with your opponents brought, but during the times when Alexis kept a baby monitor near the front door to make sure he didn't sneak out, it had to do.

But the stakes were low and no one was taking any chances, and only a few moments later Castle found himself logging out.

His eyes shifted towards the cell phone that was lying on his desk, neglected all night. A small voice inside his head, which sounded strangely like his daughter, was telling him what a bad, bad idea it was.

Luckily, Castle was a professional at ignoring advice.

The phone rang once, twice, three time until a tired voice answered on the other side. "Beckett."

"Did you know that the male brain weights 150 grams more than the female brain?"

Beckett groaned and put down the steaming cup of coffee she had just fetched. She was alone at the precinct, finishing up paperwork so that Esposito and Ryan could have their 'together time'. It's not that Beckett minded; because of the discrimination that was all too common in their line of work, the partners still kept their relationship a secret and Beckett was used to covering for them. But no one had told her that it would include being constantly bothered by an overactive 8-year-old with a writer's block.

"What do you want?"

"What's with that tone of voice? I just wanted to say hello to my favorite detective."

"Uh-huh. Like how you just wanted to chat when you showed up at my door with two bottles of wine and blindfolds."

"Exactly."

"Look.." Beckett sighed and rubbed her temple with her free hand. "We're both supposed to be working. And in case you're unfamiliar with the definition of work.."

Beckett's sentence was cut short. "Oh, don't mind me, I'm not gonna bother you. It just warms my heart to know that you're on the other side of the phone."

She rolled her eyes but made no effort to end the call – as annoying as he tended to be, the writer could easily beat caffeine at keeping her awake.

A comfortable silence settled between the lovers, only disturbed by the faint sound of a pen scraping paper and the occasional sip of coffee. Castle propped his feet on the desk and let his eyes wander around the room, but it wasn't long till he opened his mouth again.

"So.. what are you wearing?"

Beckett snorted. "Really, Castle? Phone sex?"

"Who said anything about sex? I'm honestly interested in your current choice of outfit."

Another eye roll. It seemed to have become a staple in their conversations.

"What are you expecting me to say? Tell you about how wet I'm getting just thinking about your big.. hard.. cock."

Even though her voice was dripping with sarcasm, Castle could feel his member stir at the thought.

"Oh no, I know you're just too prude for that."

"Prude?" Beckett shifted in her chair. This sounded like a challenge.

"It's not like you would ever take a break from your precious work to have a little fun", he continued, knowing how much his words were irking her off.

"I can assure you that if I were there right now, my hand would not be holding a pen."

"I'm listening", Castle said as he took a more comfortable position in his chair. He was glad that Beckett couldn't see him or else she would surely be wiping that wide grin off his face.

"If something, it's working its way across your body while the other one takes a hold of your erection, stroking it tortuously slowly. When it looks like you're just about to go crazy, I get down on my knees and place small kisses along the shaft, making your pulsing cock even harder."

Her detailed narration caught Castle off guard and for once, he couldn't utter a single word. His body, however, knew exactly how to react; he had unconsciously started rubbing himself through his jeans.

"Then I swallow you whole and start sliding my tongue up and down, the tip of your length touching the back of my throat on every time." Like a lightening bolt, the words went straight to his groin. "But instead of bringing you over the edge, I pull away and start taking my clothes off, one piece at a time."

"God, you're such a tease", Castle groaned, fingers tumbling at his belt. It took him several tries until he finally got his throbbing cock out of the restrictive jeans.

Beckett bit her lip, smiling. She was enjoying this much more than expected.

"When all of my clothes are on the floor, I take my time caressing every corner of my body, fingers lingering around the place right above my collar bones that you love so much."

Castle had his head flung back and eyes closed as he furiously stroked his aching cock. He was so focused on devouring every single word that three tanks and a one-man band could have passed him and he wouldn't have noticed.

"Then I sit on top of you and, in one motion, take you all the way inside of me. My walls clench around your cock as it easily slides in and out, lubricated by my wetness."

Castle's hand sped up with every stroke and he couldn't keep the loud moans from escaping his lips.

"I guide your hand between us to rub my swollen clit and then pull you into a heated kiss, still riding your shaft like my life depends on it. Our bodies are slick with sweat and the scent of sex is thick in the air and - "

He couldn't take it anymore. "Kate", he gasped out her name as he came, the intensity of his orgasm shaking his whole body and making his eyes roll back in his head. He wasn't shaken from his haze till he heard Beckett speak again.

"Good night, Castle." Click.

Castle stared at his cell phone dumbfounded, still breathing hard.

She never ceased to surprise him.