FOUR

Kate couldn't believe it—she just couldn't believe it! It was her own fault, really; completely her own fault. Why had she thought that dating Castle would end in anything different than an explosion in her face? Things had been going so well—so well! Too well obviously; she should have seen the signs.

From the moment she left his apartment after the inaugural relationship massage, things between them went much better than she expected them to. They were more in sync on cases, finishing each other's thoughts more often than they ever had. Running case theory together had become more foreplay to them than before, and Kate constantly had to remind herself that she was not permitted to kiss him while they were at the precinct.

Even after spending the day with him, Kate found she was still excited to have him show up at her apartment for dinner or a glass of wine. Granted, that was mostly because she was excited to finally be able to kiss him and run her fingers through his hair, but she enjoyed reviewing the day with him just as much. Especially since they were finally able to say all the things they'd been holding in for so long.

Despite the thrill and excitement of those first kisses and touches, she was still glad to be sticking to her "taking things slow" plan. If they had jumped right into bed, that would have been all they thought about and those thoughts probably would have clouded their every discussion in those early weeks. Without the sex, they were able to have rational discussions (or, as rational as a discussion as one could have with Castle.)

The only down side of those first few weeks together was Gates's eagle eye upon them. It felt like every time she turned around, Gates was there, eavesdropping on what Castle said and observing his participation in the case. Kate found her gut clenching every time Gates was in earshot of one of Castle's outlandish ideas. She even tried to set him up on a few occasions so he could make a really intelligent, well-informed observation in front of her, but, per usual, he was too involved in his own wild theories to notice her prompts.

Around the fifth week she was beginning to lose hope that they'd get a case worthy of showing Castle's true talent. That was until a bizarre samurai sword wielding super hero case landed on her desk. Of course the mere prospect of a masked super hero-esque villain had Castle salivating with excitement, but fortunately his insights proved instrumental in solving the case.

When their killer was behind bars and Gates was doling out commendations to the team, she looked at him and said, "Well Mr. Castle, I guess you are smarter than you look," before glancing at Kate and walking away. As Castle griped about the backhanded compliment, Kate silently cheered, knowing that they had won the battle of the six week trial period. Naturally, Gates never said anything else about it, but that victory was enough for Kate.

Unfortunately, just two weeks later, all of Kate's excitement had vanished with the introduction of a second—and Gates preferred—consultant to her team: museum security specialist Serena Kaye. The prospect of another consultant was just plain insulting to Kate. She and her team were perfectly capable of handling the case of the murder and theft of the "Fist of Capitalism," but it seemed Serena was there to stay.

Castle hanging on her every theory made Kate physically nauseous, but for the most part a few sharp glances kept him in check. She kept her mouth shut when he seemed a little too eager to take Serena to dinner in order for them to sneak into her room, but watching him kiss her? That was completely unacceptable.

Kate's high of discovering damning evidence in Serena's possession vanished immediately when she opened the hotel room door and spotted her boyfriend's lips pressed against another woman's. The feeling was not unlike ten thousand needles piercing her gut at once and it was not one she was keen to repeat. Kate managed to resist the urge to cause too much pain as she cuffed the sexily dressed blonde and hauled her to the back of her cruiser. Fortunately, when they arrived at the twelfth, Ryan and Esposito had taken Serena to be processed, leaving Castle and Beckett to travel alone in the elevator.

The second the elevator doors shut, Kate shoved Castle into the elevator wall with her palms flat on his chest. "I cannot believe you kissed her!" she hissed.

Castle's jaw dropped and he squeaked, "Wha—I was just doing what you asked!"

"What I asked? What I asked?! When did I ever say make out with her?"

"Distract! You said distract!"

"And you heard make out?"

Castle huffed out a quick breath through his nose. "I'm sorry, but I panicked. You were coming out of the room and I didn't want her to see you so I just kissed her—I wasn't thinking."

Kate turned away from him, crossing her arms over her chest and muttering, "Clearly."

"C'mon Kate it's not like it meant anything. I didn't enjoy it."

"Coulda fooled me."

Castle opened his mouth to respond instantly, but then paused for a moment and thought about the situation. "Wait, is this you being jealous?"

Kate turned towards him with a scathing look on her face. She opened her mouth to speak, but before she could, the elevator dinged, signaling their arrival on the proper floor. With a half-grunt, half-growl, she stepped off the elevator, prepared to interrogate Serena with every ounce of Detective Kate Beckett she possessed.

Kate had to admit she was significantly disappointed when Serena Kaye was not their killer, but since they were able to put the real killer behind bars, she decided to move past Kaye and turn her disappointment and irritation on Castle. She was naturally still quite angry about his kiss with another woman, but she was also angry at his accusation that she was jealous. Oddly, she was not angry with him for that particular comment, but at herself since he had been one hundred percent accurate in his observation.

Kate was not the jealous type. She swore up and down that she was not the jealous type. Then again, she realized, she had rare occasion to be jealous. Her beauty had drawn more than her fair share of men's attention over the years and once she had it, she was almost always the one backing off the relationship. Never once had she had to fight for someone's attention, particularly not Castle's attention—at least, not until Serena showed up.

Kate quickly realized that jealousy was not an emotion she enjoyed in the least. She despised feeling irrationally angry and out of control. Which, naturally, led her to be angry with Castle for making him feel that way.

Due to her own inner turmoil, she went directly home after making her arrest and didn't speak with him until he showed up at her apartment that evening. She briefly considered pretending not to be home, but realized that was completely childish. When she opened the door, she drew satisfaction from his rejected puppy dog expression.

"You were right," he began, stepping into her apartment. "I definitely should not have kissed Serena, but I didn't plan on it—I swear it!"

"And how many other people will you kiss without planning on it?" she asked as she folded her arms over her chest.

"NONE! None I promise! Just, okay, okay how about you ban me from undercover operations? Wait-" he said quickly, a grimace crossing his face. "No, please don't ban me from those; those are awesome. Oh! Ban me from undercover ops when we're not going together!" He concluded with a smile.

"That's not the point, Castle," she sighed, walking into her living room. "What if you…I don't know…what if you meet someone who…who you…" She could feel her face flush with heat as her worst fears came to the surface; she was unable to finish her thought.

"Kate," he said softly as he approached her. He placed a hand on each of her shoulders. "I promise you that I'm not going anywhere. There's no one else. There could be no one else. I promise." With that, he leaned down and kissed her. When he pulled back, she wore a soft smile. "Okay?"

"Okay," she repeated, though somewhat reluctantly.

"Great! Now to complete my groveling…" He wiggled his eyebrows enticingly before pulling a small black velvet box from his jacket pocket.

She looked at it and then back at him. "What's this?"

"A present."

"What is it?"

"Open it."

Skeptical, Kate took the box and opened it to find square stud earrings made up of nine tiny gems. Though they could have been fake, given the flashy nature of her boyfriend, she assumed them to be real. Chewing on her bottom lip, she looked up at him. "Castle, you didn't have to-"

"Yes, I did," he assured her. "Besides, I've never given you jewelry before. Think of them as a very belated birthday present."

She blinked at him. "You gave me concert tickets for my birthday."

"Yes but this is what I should have given you," he said with an ever-growing smile.

With a sigh, Kate stood on her toes and kissed him. "Thank you."

"Always," he smiled at her.