Disclaimer: I don't own Castle. The only profit being made is my own amusement (and hopefully yours).

Five times Josh suspected Kate was in love with another man, and one time he knew for certain

1.

Dr. Josh Davidson knows a lot about hearts—the names of the vessels that supply them, how they feel as they're beating against his gloved hand—but he realizes that he'll never be able to learn enough. Still, he tries to stay on top of the latest research as much as possible. That's why, after a long day of three mitral valve repairs and one defibrillator placement, he's reading the American Journal of Cardiology's update on the long-term patency of internal thoracic artery versus saphenous vein grafts.

Kate is sitting next to him on the bed, reading a mystery novel. He gazes over at her, beautiful even in an old gray T-shirt and black tights, and wonders what the hell happened between her and Tim or Todd or whatever her ex-boyfriend's name was that she told him but he can't recall.

He takes a second look at the volume that Kate is holding in her slender hands. The author, Richard Castle, sounds oddly familiar, and it takes him a long moment to remember. "My buddy Ron from work is a huge fan of that guy," he tells her, tapping the spine of the book.

She glances up, green eyes widening in delight. "Really?"

"Yeah, Ron keeps telling me about those books. He annoyed the whole department a couple years back when the author killed off Derrick Storm and he would not stop complaining about it."

Kate has a little smile on her face now, a lot like the one he'd seen the night they'd met at T.J. McChucklenuts and he'd mentioned his motorcycle. "Rick Castle spent most of last year at our precinct, you know. Doing research for his books."

Josh can't wait to see how Ron will react when he hears that Richard Castle was at his girlfriend's workplace. "Think he'll base a character on you?" he teases.

She looks uncomfortable now. "Actually, yeah, he has. His latest character is a female homicide detective." She rolls her eyes and shakes her head and makes some waving gesture with her hands, and Josh can see she's part flattered and part embarrassed to be inspiration for the main character in a series of mystery novels.

It all makes sense now. "Nikki Heat!" Josh exclaims, laughing. "Kick-ass, sexy cop chick. That's you?"

Kate's laughing now too, and she looks more stunning than ever. "Yeah, I guess so. Who would've thought, huh?"

"I'm not the only one who thinks you're hot," Josh replies, and she rewards him with a demure smile. He suddenly has a thought. "Hey, Ron's birthday is coming up in two weeks. Any chance we could get Mr. Castle to sign a book?"

Kate sighs sharply, presses her lips together, and mumbles, "Sorry, he's not around anymore. He left to spend the summer with his ex-wife." Josh thinks he detects a note of bitterness in her voice, and he briefly wonders if Kate ever had any interest in the famous author, who, judging from the cover of Storm Rising, is the charming kind of handsome.

He decides it doesn't matter—Kate is with him and Richard Castle is with his ex-wife. And Ron is going to stop bragging about how he went to the better medical school when he finds out that Dr. Josh Davidson is dating Nikki Heat.

2.

The shrill ringing of Kate's cell phone jolts him from a deep slumber. He glances at the clock as the room slowly comes into focus. 8:37 am. It's one of those rare mornings when they both have the day off, and they had planned to make breakfast together and spend the morning watching old Broadway musicals.

"What is it, Castle?" he hears her say. There's the slightest touch of morning brusqueness in her voice, but there's something else, too, something that he can't quite identify but wants to call cheerful. The conversation continues, mostly intrigued mm-hmms and rights and okays from Kate, and excited chattering from the other end of the line. "All right, I'll be there in half an hour," she finishes.

"Castle has an idea about the crime scene," she announces. "I'm going to go check it out."

He groans. "It's your day off," he grumbles. "Can't you stay for just another hour? At least for coffee?"

"Sorry, babe. It sounds like it might be a good lead." She grabs some clothes from the dresser, disappears into the bathroom, and is out the door five minutes later with tousled hair and no makeup.

He knows he shouldn't be complaining, after all the times he's gotten out of bed at 4:30 in the morning to round on his patients before the first surgery of the day. But this is different. In his case, it's a requirement of his job. Kate didn't need to visit a crime scene on her day off just because Castle had some crazy theory. But she'd gone, willingly and perhaps even eagerly.

He's well aware that famous novelist Richard Castle has a bit of a thing for his girl. He's known it from the moment they stood face to face and Castle asked what's there to tell?, as if he was almost afraid to find out. Now he wonders if Kate has any feelings for the man beyond a simple colleague status. After all, he's heard plenty about Castle's silly stories and precinct pranks, but Kate hadn't bothered telling anyone at the 12th about having a boyfriend.

Josh decides to dismiss these wayward thoughts and blame them on the twelve hours that he spent in the operating room the day before. He covers his head with the pillow and goes back to sleep.

She's still gone by the time he wakes up properly.

3.

They're lying in bed, skin to skin under the covers, as their pulses slowly return to normal. "Best Valentine's day ever," Josh murmurs, as he kisses her hair, her forehead, her cheek, her mouth. Slow and gentle, unlike what had just happened between them minutes before.

Kate pulls away suddenly and takes a deep breath. "I have something to tell you," she says quietly.

He nods, prompting her to continue.

"A few weeks ago, Ryan and Esposito were taken hostage while we were working a case. We tracked them to a warehouse. I went to the place with Castle. There was a guard outside. We couldn't call for backup without him seeing it and tipping off his partners."

Josh listens, transfixed and horrified. He remembers his flippant remark to Kate's team—catch any bad guys today?—but it's never really registered that this involves his Kate in danger, running to abandoned buildings in the middle of the night, criminals prepared to shoot her if she got too close. He puts his hands against her back and rubs his fingers in little circles against her skin, trying to reassure himself that the peril is over, at least for now, that she's warm and alive in his arms.

Kate continues with her story, apparently unaware of his reaction to the tale. "So Castle and I left the car and tried to distract the guy, but he wasn't buying it. He was coming towards us and looking at his gun and I could tell he was thinking about using it"—she's breathing quickly now, remembering the moment—"so I was getting ready to shoot him first. And all of a sudden Castle grabbed my hand and kissed me. And the guard actually turned around and I managed to knock him out. So that's it. I kissed Castle and you deserve to know about it. Will you forgive me?" Her green eyes are fixed on his, and he can see the fear and guilt in their depths.

He pictures Castle's mouth on Kate's, touching her, tasting her, and the images bring a rush of jealousy and anger. These quickly give way to scenes of Kate falling to the ground, clutching her chest in pain as dark red blood pours onto the cement outside of the warehouse. He wraps himself around her, pulling her close against him. "Oh, Kate, baby," he whispers, as he kisses her jaw, her neck, her collarbone, her shoulder, everywhere. "I'll forgive anything you had to do to stay alive, I promise. Just as long as I know that you're mine. That what you did with Castle didn't mean anything to you."

He can feel her shaking her head as her soft hair tickles his temple, feel her sigh against his lips. "No. No, it didn't mean anything."

He reaches for her hands, clasping them as tightly as he can. He believes her, of course. Kate Beckett is the most trustworthy and loyal woman he's met in a long time, and he knows that she would never be capable of cheating on him.

But she's looking down, staring at their joined hands instead of into his eyes, and he's not so sure that she believes herself.

4.

Josh realizes that this is how his patients' families must feel, sitting in the row of plastic chairs outside of the operating room and waiting for their loved ones to come out of surgery. He's in the backseat of Detective Ryan and Esposito's squad car, helplessly watching through the window as the two detectives disappear around the corner in search of Kate.

It had been almost an hour since he'd knocked on the door of Kate's apartment, armed with flowers, Chinese takeout, and an apology, only to discover that she wasn't home. She hadn't answered her phone. He'd called the precinct in a panic, but she hadn't been in contact with them either, and even worse, Castle had gone missing, too. His initial reaction had been anger—what the hell was Kate doing out with Castle in the middle of the night? But now, the jealousy is gone, and instead he runs through the terrible scenarios in his mind. Was she suffocating in the trunk of a car? Was some creep holding a gun to her temple? Or—he tries not to think about the other possibility—was she already dead?

He hears running footsteps approaching. Two uniformed cops are carrying an unmoving Richard Castle. Detective Esposito is cradling Kate in his arms, with Detective Ryan right by his side. Josh bolts out of the car and races to Kate. Her eyes are closed, her lips are blue, and there are ice crystals in her hair. He reaches for one of her hands, finds it ice cold, moves his fingers to her wrist. He thinks he can detect a thready beat, but he can't tell if it's her pulse or Esposito's movements that he feels. "Kate!" he yells. "Kate, can you hear me?"

"Josh, don't just stand there, damn it! Call an ambulance!" Esposito barks at him.

And it's like he's in medical school again, on his first day in the operating room, stupid and useless and getting yelled at because he didn't know what the hell Metzenbaum scissors were, except this time it's not his pride at stake but Kate's life. He reluctantly releases Kate's hand to reach for his phone, his fingers shaking so hard he barely manages to clumsily dial 911.

When they arrive, the paramedics ignore his protests of but I'm a doctor, and they kick him out of the ambulance. So he paces back and forth between the two ambulances, Kate's and Castle's, the tension in his muscles gradually dissipating as he listens to the reports of temperature normal and heart rate steady and going to be all right.

"Dr. Davidson?" calls the paramedic taking care of Kate. "She's waking up." Josh runs over and starts to climb onto the ambulance, but the man holds up a hand. "Just stay right outside, sir, and I'll let you up here as soon as I can."

"What time is it?" he can hear Kate demanding. "Oh, my God. The bomb. Where's Captain Montgomery?" There's panic in her voice, and it sends a shudder through his body as he realizes there's something serious going on that he doesn't know about. "The bomb. I need to—"

"Please calm down, ma'am," the paramedic orders her. "Your boss and your team are here. They're doing what needs to be done. What you need to do right now is relax. You're suffering from a mild case of hypothermia. Now, look. You have a visitor."

Josh is looking down at her, lying on the gurney, before the paramedic can even finish his last sentence. She stares at him for a moment, and he imagines he sees a trace of disappointment on her face that quickly gives way to fear. "Castle," she blurts out. "Where's Castle?" Josh can hear it, the concern and terror, and for some reason he feels his own chest constricting.

"He's going to be fine, babe."

"He's alive," she whimpers, throwing her arms around his neck and resting her cheek against his. As he runs his fingers through her damp and rumpled hair, he knows that the bomb and Captain Montgomery have been momentarily forgotten. She pulls back to look at him, and he sees the relief and joy written all over her face. "And you came back," she whispers, leaning forward so that their foreheads and noses are touching.

Castle's okay and they're okay. Josh can't tell which of these two things is the bigger reason for her smile.

5.

"Do you ever miss it?" Kate asks one evening, as they're watching a public television special about malaria in sub-Saharan Africa. She's lounging on the other end of the couch, cup of tea in hand, her feet in his lap.

"Miss what?"

She gestures at the TV. "Your global health missions," she says.

He's about to say no, but he quickly decides that Kate deserves the truth. "Yes, a little," he admits. "But I'm still going to do one trip a year."

Kate keeps her eyes fixed on the television screen, even though he's certain she's not watching the volunteers put up mosquito nets. "It's not as much as you did before. I don't want to feel like you're changing who you are because of me."

Josh puts a hand on one of her ankles, running his hand under the hem of her pants to stroke her shin. "I'm not changing who I am. I made a choice. I want to be here, with you. Because I love you, and I think you're worth it."

He thinks any other woman would be delighted to hear her boyfriend make such a confession, but Kate just looks at him with an unsettled expression. "I feel—I don't know—guilty, I guess, that you didn't go to Haiti. That you're making this huge sacrifice and I haven't really done anything for you."

She's somewhat correct, he realizes, once he stops to think about it. She's invited him to lunch with her dad a couple of times. She doesn't go to the Old Haunt with the guys anymore after work. But he still senses the distance between them, like he does now, with her sitting so far away from him that he can't even put his arm around her.

He beckons to her to come closer, and she obeys, scooting over to him and leaning her back against his side. He slips an arm around her waist and absently strokes her stomach through the thin fabric of her threadbare shirt. "There is something you can do for me."

"What?"

"Tell me things. Tell me about your family, about why you became a cop. I want to feel like I'm as important to you as you are to me. Like I'm more than someone you just spend the night with."

So she does. He listens as she talks about the alley, the years of obsession, the ordeal her father went through, the nightmares that still come every few months. She tugs on the chain around her neck and hands him her mother's ring, then places take her tiny wrist in his hand to let him study her father's watch. He admires the solidly built timepiece, the glass surface that's barely scratched. "You took such good care of it," he observes.

"He had it a long time and it was actually pretty beat up," Kate admits, pulling her wrist away from him and running her other hand over the watch. "It was ruined when my apartment blew up last year and Castle got it repaired for me."

Josh feels her stiffen, as if she regrets her words and wishes she could take them back. An uncomfortable sensation begins to grow in his stomach as he realizes what she's just admitted. "Castle knows all of this? You told him?"

Kate nods slowly, saying nothing. Josh holds her small frame tighter against his body, but it doesn't help him feel any closer to her.

His initial joy that she's finally opening up is tempered by the knowledge that she trusted Castle long before she met him. He tries to assure himself that Castle has never seen her naked, never heard her moan in pleasure, never woken up next to her—and yet she's shared her deepest secrets with Castle, and Josh can't help wondering what else there is between them.

1.

Josh eagerly climbs the stairs to the rooftop picnic area of Castle's apartment building. The party was supposed to start at six in the afternoon, but his anesthesiologist had been running late, and so he'd left a message with Kate, apologizing for the hold-up and promising that he'd meet her there.

As he opens the door to the roof, he's instantly struck by the savory smells of barbecuing meat. He sees Captain Montgomery and an elegant woman who's probably his wife, sitting down and chatting with Detective Ryan and a pretty blonde who's clinging onto his arm. Detective Esposito and Kate's sassy medical examiner friend are nowhere to be seen; Kate's shared a bit of juicy gossip about the pair with him, so he has a couple of ideas about where they might be at the moment.

Then he spots Kate and Castle at the grill, standing close but not quite touching, and he can hear the two of them laughing as they flip the hamburger patties and hot dogs. From the way Kate is turned, she should be able to see him smile and wave at her, but she doesn't even notice him approaching, for her eyes are fixed on Castle's face. It's the same look he'd seen in Castle's gaze, that day of the bomb scare when he'd interrupted the two of them talking in the precinct hallway. His Kate looks comfortable, content, and completely smitten.

Even from a distance, he can sense the pull between the two of them, and he can tell that they're both trying to resist it, as if it's a magnetic force that will propel them toward each other if they dare to get any closer than they already are. It's part sexual tension but Josh intuitively knows it's more... complicated than just that. There's not only lust, but also respect, trust, friendship, and maybe even something like love.

Josh takes a few more steps toward the barbecue, then hesitates. He knows that he's Kate's boyfriend, but he can't ignore the feeling that to come any closer would be to intrude on a moment that's private and incredible and real.

Dr. Josh Davidson knows a lot about hearts—enough to understand that Kate's will never belong to him.

FIN.