Because songfics are apparently not allowed and I had to delete a previous story...please listen to Speechless by Dan and Shay for my original idea.

Castle didn't mind most of the undercover work he'd done. In fact, he loved undercover. It was like he got to live the lives of the characters he could only write about. The only times the undercover haunted him, was when Beckett wasn't by his side.

But tonight she would, in fact, be by his side. And tonight, he'd have the prettiest girl on his arm-even if they were supposed to be 'working'. This outing was for informational purposes only. They'd be infiltrating the shady dealings later.

Castle pulls up to Beckett's apartment building and his phone vibrates in the cup holder. Gina. Again. And then a lengthy voicemail. Castle rolls his eyes knowing that it would probably be an extension of the conversation he had to cut short at the house. He was home 'early' but he was only able to stay long enough to kiss Alexis goodnight and grab a few nice outfits for the sting. Gina was less than thrilled. Even less so when he told her he had to pick up Kate. His wife always hated when he didn't call his work wife by her last name. She felt it too personal.

Gina wasn't clingy but she always thought Kate had something she didn't. While true, it was true in a different way and it wasn't easily explained, much less to himself. It was like when Alexis couldn't untangle her headphones. At least he could untangle those...feelings were a little harder.

Speaking of feelings, Montgomery would have a few of his own if they were late. Castle turned off the car and went up to Beckett's apartment and knocked.

"I'll be ready in a sec!" Kate opens the door and then disappears around the corner again. Castle catches a streak of black and knows she plans on wowing the crowd tonight. It was a long-sleeved, knee-length dress with one of those fancy necklines he could never name. It was wide at the top like a box but ended up looking like a crystal point at the end. Women's clothing confused him. Men's were much simpler. He'd learned that one a long time ago. He remembered Beckett wearing it on the last sting they'd done as a 'couple' and was fending off creeps all night. Then again, did they ever work with not-creeps?

From her quick duck around the hall, he smelled her perfume lingering. It's Coral by Skylar. Castle had bought it once for Gina at Kate's suggestion after being at a loss for Christmas gifts. Gina never wore it though. She didn't like being associated with her husband's partner. She'd somehow known that's where he got the idea and realized that it probably turned her off to it even more.

Sometimes he just didn't know what to do anymore. How could he make the two women in his life as happy as he could reasonably make them? They were drastically different and often found that detail working against him.

But he pushed Gina out of his mind. He had Beckett to focus on and it was a kind of relief that loosened his inner qualms for the night.

Except now, he found those inner qualms being about remembering Gina instead of the beautiful woman soon to be on his arm for the night. It wasn't wrong to say she was beautiful, right?

Again, pushing the thoughts out, he took a few paces and hung on the door jamb to her bedroom without crossing the threshold, "Kate, you do know we're supposed to blend in, right? Because you're gonna steal the show in that." He says, with just enough laugh in his voice,

"Oh, do you think I should change? It's the neckline, right? Are the heels too much?" Beckett flusters with herself for a moment.

"Will you pinch my ear if I say the neckline looks really good?" Their easy, sometimes double-edged banter was a hallmark and he really couldn't imagine their relationship without it. The sarcasm covered up the blatant feelings yet they couldn't bring themselves to stop.

"Only if I can say I have a thing for light blue button-ups." She smiles, fixing the collar of his shirt.

"Yeah, that's fine by me." He laughs, handing her the silver clutch laying on the bed.

Beckett laughs, leaning in and nudging him as they stroll down her hallway and to the car. It's light and carefree and fun and if someone didn't know any better they probably wouldn't know they weren't a couple. It was a blessing and a curse.

The car ride to the rendezvous point is soft and comforting. There aren't many words past the usual but they've gotten to a point where words weren't always necessary. It was calming and didn't require being 'on' all the time.

They arrive around the block from the sting site and Montgomery comes out of the back of the mobile TARU van.

"Ok, so here's your earpieces and we'll be feeding you info. Nothing crazy tonight, just test 'em out. You'll make the brass happy if you make it out without any ruckus."

"The brass?" Castle questions,

"They were not thrilled with me for sending you two. They thought you two were too close and the people who'd care would get the wrong idea."

"We're professionals, sir. They know that." Beckett says firmly but not truly upset.

"Oh, they know it too, don't worry." Montgomery said, not pursuing the topic longer, knowing that their assessments were definitely on to something. Everyone saw it but them and he knew they'd have to work it out themselves or it'd be a disaster. Then he ran the risk of losing his two best detectives. The one he treated like a daughter and the other who reminded the aging man of what life offered.

"Alright, off you go." He shoos the duo away and crawls back into the van to watch from the command center.

At the door of the fancy club, he held his hand and without looking him in the eye or making a big fuss, she took it and they started working the room together.

In the beginning, he didn't say much; he was too busy watching Beckett talk. A discreet squeeze told him to get his act together. He tried, he really did.

After exhausting their options with the couples, they decided to split up for a moment, hoping to get more specific details out of the potential suspects than they would together.

Castle watched Kate observe and single out other club patrons. There was something about the way she smiled at her target that instantly brought him back to their first meeting.

SOME YEARS EARLIER

Castle had just killed off Derrick Storm and was looking for a new direction in his career. Venting to his daughter, of all people, he turned at the sound of his name.

"Mr. Castle?"

He didn't even bother to look, Sharpie in hand, until he realized it wasn't a fan. There was a tall, professional, no-nonsense detective flashing her badge at him. He immediately noticed past the work casual attire and was captivated by her striking green eyes and bobbed Bordeaux-red hair. If he were describing her in one of his books, he'd point out her beautiful fair skin and excellent bone structure. Plainly put, she might be the new direction he so desperately needed.

"Detective Kate Beckett. I'd like to ask you some questions about a murder that took place earlier tonight." Castle didn't know what he was expecting when he heard his name called but it certainly wasn't her.

As they devolved into solving the Tisdale murders, he knew the way they could antagonize the other was going to be the beginning of a lasting friendship.