A/N: Hi guys! I'm very excited about this story-it's one of the longest I've ever written! It will be 26 chapters + prologue & epilogue.

Also, I want to be upfront about the posting schedule. I will update 2x a week when Castle is not airing (so for the next 2.5 wks), then only 1x a week during those next 4 weeks. Then, when we hit hiatus it'll be back to 2x a week.

Edit 6/3/15: thanks to lordofkavaka for the awesome cover art!

Enjoy!

Prologue (September)

Kate Beckett impatiently tapped her foot against the worn tile floor of the NYPD's Twelfth Precinct. Reading the memo on her computer screen all she could think was: This is bad, very bad. So bad, in fact, it was quickly approaching "worst day ever" territory. It was terrible enough to discover the good reputation of the NYPD had been sullied once again by a cop on the take—a captain, no less. But now this—a partner reassignment? The day was getting worse and it wasn't even nine a.m.

Okay, she told herself. She could handle this. She had partners before and just because she had gone over two months without did not mean she had deluded herself into believing she would be partnerless forever. No, that wasn't how the NYPD worked. And, she thought, forcing herself to see her coffee mug as three-quarters-full not one-quarter-empty, perhaps this wouldn't be so bad. Maybe she would not get stuck with a rookie for a partner; that would definitely make things worse. She had neither the time nor patience to train someone green. Hopefully, her new partner would be seasoned enough to know the ropes. Or, at the very least, know how to handle himself in the field outside of whatever bullshit they were preaching in the academy this week.

Still, she had sixty-eight agonizing minutes to wait for the identity of her new desk-mate. Why couldn't Captain Montgomery have at least listed the names of the three transfers into their division? Then she could have at least prepared herself ahead of time. Though, to be fair, she was not overly familiar with the homicide cops at the ninth. It was entirely possible that had their names been listed she would not have had any more information than she had without them.

"Beckett." Detective John Anderson nodded to her as he walked into the bullpen and took the desk two spots to her left. She offered a soft smile in response.

Kate casually sipped her coffee mug and watched as Anderson logged onto his computer and read the memo she had discovered not fifteen minutes earlier. His shoulders hunched and his head ducked as he read. Though she couldn't see his face, she imagined his brow quickly filled with dozens of wrinkles; it always did when he was confused.

Anderson was a good guy; a good cop. Twelve years her senior he had been a cop longer than she had been an adult, but he never made her feel that way. From day one, he'd treated her like an equal, even though she was greener than Kermit the Frog. And, unlike his partner, he was always willing to offer a helping hand.

A few minutes after he sat down, Anderson turned his chair so that he faced Kate, the dark skin on his face filled with worry lines. "You see this, Beckett?" he asked just loud enough to be heard over the distance.

She nodded. "You don't know who the transfers are, do you?"

Anderson shook his head. "No; this is the first I'm hearing of it. I guess you'll be getting one of the new guys as a partner, won't you?"

"Seems that way."

"Good luck," he told her and she knew his wish was genuine. After his partner had retired the year before, he was suck with Dan McCreary, the eager newbie who may as well have had "douche bag" tattooed across his forehead; they both knew how well that had worked out.

Sixty agonizing and completely unproductive minutes later, the bullpen was beginning to fill. All the on-duty detectives and beat cops had arrived. Groups of them were clustered together throughout the homicide floor presumably talking about the impending announcement. In addition, three new faces had appeared, though Kate couldn't say she recognized any of them. Two of the men-one a stout Hispanic and the other a six-foot-six Caucasian who presumably was a basketball player in a former life—looked younger than her. Rookies. Please don't let either of them be my partner, she silently wished.

The third man stood apart from the other two. He was tall, though not as large as Larry Bird's protégé, but he had similarly pale skin and chestnut hair. He wasn't unattractive, but his handsomeness came in a rougher, rugged sort of way. If she was forced to guess his age, she would have said mid-to-late thirties, though his rumpled sport coat and wrinkled shirt collar certainly weren't doing him any favors. Kate decided to hope this man would be her partner, though her wishes were based solely on his age and thus experience level.

Before Kate could examine the newbies any further, Montgomery called the attention of the room. Standing outside his office, his booming voice carried easily across the entire floor.

"If I could just have everyone's attention for a few minutes I will try and get this over with as quickly and painlessly as possible. By now I'm sure you've all heard about what went down at the ninth and I'm certain you'll all agree with me when I say we'd like to put this incident behind us and move forward together—stronger.

"At this time, I would like you all to welcome three new people to our team. Men." Montgomery beckoned the three transfers forward and they joined him standing in front of the glass windows of his office. "We have Nathan Carver and Jason Sanchez," Montgomery said, gesturing towards the younger two men, "and Richard Castle."

"Son of a bitch," Kate hissed under her breath. Richard Castle. Richard Castle!

Oh no—take it back! Take it back! Her brain screamed in a desperate attempt to retract her earlier wish, but it was too late.

"Carver will partner with Smith, Sanchez with Timothy, and Castle will be with Beckett."

Kate resisted the urge to groan aloud. This wasn't happening; this could not be happening.

Though she had never seen his face, she certainly had heard of Richard Castle. Despite being older than her, Castle had only been on the force about the same time she had, though they had always been in different precincts. His reputation, however, had made the rounds. Simply put: he was a loose cannon.

He was always hot-rodding. Making crazy and often dangerous arrests. They were good arrests, but Kate believed the dangerous aspects under which he apprehended suspects negated their values. She was by the book and from what she heard he broke every rule he could get his hands on; this was going to be a disaster.

"Beckett?" Montgomery's voice pulled Kate from her internal fury. She looked up to see he stood with a grinning Castle by his side. "You two haven't met before, have you?"

"No, sir," Kate said before turning her eyes to her new partner. Partner. Ugh. The mere thought made her skin crawl.

"It's a pleasure to meet you," the male detective said, extending his hand.

Kate shook it with great suspicion. She mumbled a hello to her new colleague before turning to her superior. "Sir, may I have a word?"

Montgomery nodded and Kate pushed past the two men to lead the way into his office. Once they were both inside, she shut the door. "Sir, I think I would really prefer to be partnered with Carver or Sanchez."

"I know." He smiled at her. "That's why I put you with Castle."

She folded her arms across her chest. Okay, this had officially crossed into worst-day-ever territory. "Sir, are you punishing me?"

The captain chuckled. "What would I be punishing you for, Kate?"

She shrugged. "Being harsh on the idiots you partnered me with before."

That time, Montgomery let out a full laugh. "No, I'm not punishing you Kate; I'm giving you the opportunity to mentor someone."

Kate blinked. "Isn't Castle older than me? By, like, a decade?"

"He is, but you've been a detective for longer. You're the best I've got, Beckett and I'd like to see some of that brush off on someone else."

"You're buttering me up," she accused.

He smiled. "Is it working?" When she didn't respond, he continued. "Listen, Kate, Castle might not be the person you chose, but he's not a bad detective. His case closure rate is very good, in fact. He just needs someone to…" Montgomery let his voice drift off as he tried to find the right term—one that would not offend her.

"Kick his ass?" she offered.

"No. Encourage him to stay on the right path, shall we say?"

Kate grumbled. "Do I have a choice?"

The elder man smiled devilishly. "No."

"Fine. But," she warned, "I'm not promising this will last longer than any of the others."

Out in the bullpen, Richard Castle stood beside his brand new desk. He skimmed his fingers overtop the clean keyboard and then down to the smooth wooden surface. It wasn't the same as his desk at the ninth, but it would work just fine—especially if it enabled him to stare at the lovely lady detective all day long. What had Montgomery said her name was again? Right—Beckett. Kate Beckett.

Damn. She sure was a hell of a lot different than his previous partner, the oh-so-very-green Marquez who had the luxury of not being transferred.

Truly, he was not one to shy away from change. If anything, he welcomed a different routine now and then as monotony drove him crazy, but he couldn't say he was thrilled to switch precincts. His trepidation merely stemmed from the situation; he feared other detectives would view him as tainted or suspicious since his previous captain had been dirty. That could not have been further from the truth, which simply meant he had to work extra hard to prove that with his new coworkers. After all, he could not afford to have another failed career on his hands.

"Hey Castle." A voice from behind pulled him from his thoughts. Castle turned to see a man several inches shorter and more than several years younger than him. He recognized this man. They had worked together a few months prior on a case that crossed into his jurisdiction, but he could not remember his name.

"Oh, hey, you're-"

"McCreary. Dan McCreary," the younger man said, holding out his hand.

Castle smiled and shook it heartily. "Right. McCreary. Well, at least I know one person, right?" He forced a laugh and then slipped his hands into his pockets. "So what can you tell me about my new partner?"

McCreary laughed. "Beckett? Good luck."

Castle's brow furrowed. "What does that mean?"

"She's a black widow; eats hear partners alive. Must have been through four of them in the past year," he explained. Castle's eyes widened with surprise. "She's cold as hell, but I guess that's what makes her so good. She's got the best case closure rate at the twelfth…unfortunately," he added with a mutter, his tone clearly indicating jealousy.

"Interesting." Castle exhaled as his eyes drifted towards the captains office, where she stood with her arms folded.

"Just don't expect a smiling face from her every morning—or ever."

After McCreary walked away, Castle continued to watch Beckett in Montgomery's office. Black widow, huh? Well, that was alright with him; he could handle a challenge. Besides, she couldn't possibly be that bad.

Not two minutes later, Beckett stormed out of the captain's office and returned to her desk. Seeing his opportunity to make nice, Castle approached her with a smile and the usual spring in his step. When she sensed his presence, she glanced up at him, annoyed.

Suddenly, Castle found himself rendered speechless. Upon their initial introduction, he hadn't fully taken her in, but now he had the opportunity. Her hair was chopped short and spiky in a maroon-hued color much too dark for her. Her nose and lips were of good proportion and while she had cheekbones that could be seen from a mile away, it was her eyes that struck Castle. The chestnut pools flecked with emerald reflected back a crushing amount of determination, pain and a little bit of fury.

"What?" she asked him; she couldn't have sounded more annoyed if she tried.

"You have gorgeous eyes," he responded without much thought.

They narrowed at him. "That's sexual harassment."

"Wha-I…ah." Shit. What? Had he said that aloud?

"Sexual harassment, Detective; it's in the manual."

"But-I, ah was just complimenting you," he stammered stupidly. Well this was one hell of a way to start a new partnership. Idiot.

"Well, don't." Her response was short and simple before she turned back to her computer screen.

Somewhat dumbstruck, Castle walked to his seat and sat down. Okay, this was bad, but he could fix it. He leaned to his right so that he could see her around their back-to-back computer monitors. "Look, I think we got off on the wrong foot here, Kate. I can call you Kate, right? We're going to be partners and I just wanted to-"

"Listen to me, Castle," she said, spitting his name like it was a curse. "I've worked very hard to get where I am and I won't have some half-cocked hotshot come in and mess up my career. If you get in the way of my investigations, I'll bury you. Got it?"

Wow.

How was it possible she got even hotter when she was threatening him?

"I, ah, yeah, Beckett; yeah, I got it."

"Good," she said. Then, without another word she turned back to her computer screen. This was definitely the worst day ever.