A/N: This story would not exist without the prompt offered to me by operaluvr. I don't normally write to prompts, but this idea felt so strong that it spoke to me. So, thank you for the inspiration. I hope you like how it turned out. This is chapter one of two. The prompt is at the end of the chapter.

No Such Thing As Coincidence

She can't get the image out of her head: the way Castle had looked at her when she walked across the bullpen earlier tonight wearing that strapless black gown. Beneath the intensity of his burning, almost possessive gaze, all the dark and dirty looks, the stony silences, and the coldly cryptic remarks seemed to coalesce into one thing and one thing only: Castle's performance over the past few weeks had been a big fat lie. After tonight, she'd almost stake her pension that he still cared about her. She just can't explain his behavior.

Even now, hours later, it still sent a shiver of hope rushing through her to recall the surprise and the longing in Castle's eyes.

She had turned her share of heads, both as a girl and an adult woman, but nothing had prepared her for the searing scrutiny her erstwhile partner had put her under tonight. She didn't think she'd ever be able to forget it and, in a strange way, nor did she want to. His face had betrayed a deep yearning mingled with regret, hurt and a sense of having missed a golden opportunity, all of these emotions having passed across his eyes in the space of seconds. And how it haunted her. In that moment she had wanted to banish everyone from the entire homicide floor so that they could be alone, and then she would have told him that if the look on his face matched the tenor of his heart then they most definitely weren't over. No chance had been missed; their timing was just a little off. They could never be over so long as he still looked at her like that.

But that little tableau was the stuff of fantasy, she knew, and so she had walked out the door on the arm of Colin Hunt, forced, as ever, to be responsible and to focus on the job. First, last, and always.

In any case, her dream scenario ignored the fact that Castle had made his position clear when he had shown up at her crime scene the other day with a blond flight attendant in tow, and then he had given this stranger the keys to his Ferrari no less. She would do well to take a hint before she embarrassed herself further. From a professional standpoint, she knew that looks could be deceiving. She thought she'd seen the face of innocence hundreds of times in the past, only to find out later that she had been looking into the eyes of a stone cold killer all along. Looks could be deceiving, but you couldn't argue with a blonde in a hot car after a spur of the moment trip to Vegas. Those were the facts she had to work with. All the wishing in the world wouldn't change them. Those were the cold, hard facts.

The dress didn't exactly fit inside a police locker. She hung the gown as best she could, feeling slightly guilty as she looked down at the puddle of fabric she was forced to leave to pool on top of her evening shoes now that she had changed back into her street clothes. Inspector Colin Hunt was waiting for her downstairs. They had closed their case, he had asked her if she wanted to grab a celebratory drink before his flight back to London, and since Castle had made it abundantly clear that he had moved on, she had neither the excuse nor the heart to refuse.

Hunt was leaning against the wall of the precinct lobby when she exited the elevator. His bag was on the floor by his feet, and he was furtively checking his watch.

"Did I keep you waiting?" Kate asked. She frowned at the screen on her phone, checking the time for herself because she had made sure to change as quickly as possible.

"Nope. Just wondering about the state of security at Newark."

Kate, fresh from the recent cold-shoulder treatment at the hands of her own partner, was feeling more thin-skinned than usual. She immediately began backtracking, offering Hunt a way out. "Look, if you're worried about missing your flight, we can take a rain check. No harm, no foul." she said, holding up her hands and preparing to walk away.

"We could. Or…" Hunt's eyes were twinkling mischief.

Kate felt herself smiling in response. "Or?"

Colin Hunt smiled back, the effect both boyish and charming. "Or you could give me a ride out to the airport, and we could get a drink in the bar once we get there?"

Kate paused just a beat too long, and Hunt jumped back in immediately. "Look, just say if you have other things to do. I know it's out of your way."

But what Kate was really thinking about was going back to her empty apartment to brood, knowing that Castle was most likely out on the town with his new squeeze, Jacinda.

"Honestly, Kate. A rain check is—"

"No! Let's do it," she said. She jerked her thumb towards the front of the building before she could change her mind. "My car's just outside. The rush should have passed, traffic should be light. Plenty of time to get a drink and still make your flight."

Given the late hour, the airport was quiet. It shone like an ice cube lit from inside when Kate dropped Colin Hunt by the curb to check-in, and then went to park her car.

As she walked towards the terminal building five minutes later, she had to talk herself into shaking off the gloomy mood that kept settling on her shoulders. They had cleared their case. It was a significant win, one that would garner her some international recognition and goodwill. Besides, she hadn't come all this way to be poor company, leaving the English police inspector with a bad impression of American women to share with his Met pals back home. He was a nice guy, good at his job, friendly and polite. After tonight she would never see him again. She could raise her game enough to have one last drink with a valuable, international colleague. She might even enjoy herself, Castle certainly seemed to be.

This sentiment, like revenge, tasted bleak and hollow.

With a smile fixed in place, she headed across the yards and yards of bland, industrial carpeting looking for the bank of British Airways' check-in desks. She spotted Colin Hunt's blond waves from a distance, standing head and shoulders above most other passengers in the thinned out, late-night crowd. But before she could get to him, a sight over at the United Airlines desk caught her eye. She slowed and did a double take, because there was Jacinda, Castle's new friend, checking in for a flight. And standing off to one side, waiting patiently for her, was Castle.

Kate battled her devastation to absorb the scene. Jacinda was wearing her uniform. So if she was checking in like a civilian instead of going straight to the crew room, she was either taking a positioning flight to pick up her next scheduled connection or she was flying home on a staff ticket. Either way, Castle and the stewardess had clearly progressed in their relationship if he was seeing her off at the airport already.

After taking in this painful tableau, Kate was seized by a panicky urge to turn around and walk away as quickly as possible, before either Castle or his girlfriend could spot her. But before she could make her escape, Colin Hunt waved to her over the tops of the heads of the people checking in around him, and she was forced to plaster on a smile and head over to the line he was standing in.

As she made her way in his direction, she thanked her lucky stars that he hadn't thought to wolf whistle to get her attention or call out her name, because it seemed as if she'd remained under the radar so far: Castle remained unaware of her presence. Small mercies at this point.

Kate fidgeted from foot to foot as she stood beside Colin Hunt waiting to reach the front of the line. He had checked-in by machine already, so his boarding pass was printed off. Now all he needed to do was drop his bag with the agent, have it weighed and tagged, and then they could head upstairs for that drink, somewhere out of sight.

"You seem a little jumpy tonight," Colin said, adding, "If you don't mind me saying."

Kate frowned a guilty frown and faked having no idea what he was talking about. It seemed evasion was a trait that belonged to her and her alone. If Colin Hunt elicited the exact same response from her, it meant that Castle had nothing to do with her reluctance to be honest in personal situations. Nope, avoidance was definitely all on her.

"Jumpy?" She shook her head. "No, I just don't like lines...or queues, I believe you guys call them," she said, a fact that was true but that also masked the reason for her skittishness tonight.

Finally, Hunt was called forward. Kate hovered by his elbow attempting to act casual while using his tall frame as a screen behind which she could hide while still observing her partner and his flight attendant friend.

She startled, giving credence to Hunt's jumpiness observation, when he turned to her and said, "Ready to go?" But there were no awkward questions or teasing remarks, he just laughed and guided her away from the desk.

He was so easy-going and non-judgmental that she almost wished he wasn't about to get on a flight and leave the country. Then she reminded herself that she had tried this kind of relationship before, with Josh, and that Castle had been right about the surgeon then as he would be about Colin Hunt now - it was easy to hide in a relationship with a man like that when little of real value was demanded by either side. Loving another person was hard, it required work, honesty, give and take. Intimate relationships functioned more or less the same way she and Castle always had as partners, forcing you to take the rough with the smooth if you wanted to make it last, accepting the hard parts if you wanted the fun. She wished she'd learned that lesson sooner. She could have saved them both a lot of pain.

As they headed towards the escalator, Kate tried to look around without being too obvious, because somewhere between the bag drop and their walk across the floor, she had lost sight of Castle and his friend.

"Looking for someone?" Colin Hunt asked, forcing her to lie once more.

His clever, knowing smile gave her pause for a second, until a trickle of passengers joined the escalator behind them forcing her to face forward and focus on the ascent to the level above.

Since Kate had no travel documents, she couldn't go through security. This restricted their choice of bars to the few on the landside of the terminal.

"There's a wine bar over there or a fake Irish pub down by area B," Kate said.

Hunt consulted his boarding pass. "My gate is in area C."

"Okay. Wine bar it is," Kate said.

As they turned to head to the left, there was a flash of blonde hair on the edge of her vision. Kate caught sight of Jacinda once more and her heart sank. She was standing talking to Castle by the entrance to the security line. Her wheeled cabin bag placed at her feet.

Colin Hunt seemed to sense her distraction because he slowed to a stop beside her to observe the scene that Kate was watching. Ever the well-mannered Englishman, he never said a word.

Kate felt as if she was witnessing an eighteen-wheeler slide, in slow motion, towards a minivan packed full of kids, and yet she couldn't tear herself away. Castle appeared to be dodging the kiss that was headed in his direction. He squeezed Jacinda's elbow, and at the last second he turned his cheek towards her so that her lips glanced off his jaw instead of landing on his mouth.

Blood pounded in Kate's ears and her face felt hot. For a second or two she thought she might be sick.

"Everything okay?" Hunt said, lightly touching her shoulder.

She came to her senses, dragging her gaze away from the rest of the farewell scene lest she witness anything more intimate pass between her partner and the flight attendant.

She pasted a smile on her face. "Uh...yeah. Everything's fine. Now, where's that drink you've been promising me?" she said with more enthusiasm than she felt.

When they got to Vino Volo, Kate found them both a seat at the bar while Colin Hunt excused himself to visit the men's room.

Before he left to go to the bathroom, he said, "Could you make mine a glass of merlot, please?" and then he placed a couple of twenties on the bar by her right hand. He was gone before Kate could protest over the cash.

She studied the list of wines by the glass, and then she ordered herself the same as Hunt, a small for her and a large glass for her companion, and then she waited for him to return.

Vino Volo was typically noisy at this time of night. People were a few glasses into a flight of wine or enjoying some tapas while they killed time before departure, and with the constant bustle of travellers coming and going, dragging their cabin bags and more through the bar, whole minutes flew by.

Eventually, the barman set both glasses of wine down in front of her. The artificial light shone through the merlot making it sing. Kate couldn't help but think of her partner who would most certainly have ordered the same thing had he been here. But then she supposed that after tonight and the scene she'd witnessed with Jacinda, the days of going out for a celebratory drink after a case closure were gone for her and Rick. Though it saddened her to think like that, based on the way he'd been acting lately, she wouldn't be surprised if he never came back to the precinct at all, and that thought scared her even more.

Kate took a couple of sips of wine and then she checked the time on her father's watch. Hunt had been gone for over ten minutes. The bathrooms were just a short distance down the hallway. Unless he'd taken ill all of a sudden, he should really be back by now. Besides, his flight to Heathrow was due to begin boarding in less than half an hour.

With the constant stream of flight calls, gate changes, and the hubbub in the bar, Kate couldn't make out any specific detail in the public announcements. As a result, she missed out on one important message.

Colin Hunt's continued absence began to concern her. She put her glass down and reached into her pocket for her cell phone, turning away from the bar as she did so to look for her colleague even as she tried calling him.

When she turned around, she felt her jaw slowly drop while her heart rate rapidly climbed. Because standing not two feet away from her was Castle, and he looked utterly miserable.

"Beckett! What are you doing here?" he said.

He was the last person she wanted to see right now, and he was asking a question she really didn't want to have to answer. Because if tonight proved that he had moved on with Jacinda, admitting that she was here with Colin Hunt would look very much like she was moving on, too, and she really wasn't.

She frowned, trying to squeeze out an answer that would be both truthful and yet vague; some middle ground that wouldn't give her partner the wrong impression. Nothing came to mind, so she went on the offensive.

"I could ask you the same thing," she said.

Castle's gaze flitted to the matching glasses of merlot sitting atop the bar. He took in the empty stool next to her, secured with her leather jacket and a scarf. When he looked back at her face, he definitely wasn't smiling. "I just got a call over the P.A. system. Told me to come here," he said, casually scanning the room for a likely culprit before landing back on Kate.

Kate arched one eyebrow. "And you heard that all the way from Manhattan? Impressive." She heard how withering and sarcastic she sounded, and she hated herself for it. Jealousy turned her into a horrible person.

Castle rolled his eyes and shook his head, and then he turned to walk away.

"Where are you going?" Kate said.

"Home. Look, this is clearly someone's idea of a joke."

"What makes you say that?"

"Well, just look around you. Do you recognize anyone else in here?"

Kate already knew the answer, but she indulged her partner by glancing around the wine bar anyway. "No."

"Exactly. So like I said, I've been setup. Maybe you have, too," he added, gesturing to the wine glasses in front of her. "Unless you're behind this?" When she shook her head, he said, "Yeah. Didn't think so. Either way, I'm heading home."

Kate had a pretty good idea what had happened. Colin Hunt was no fool, he'd been watching them circle one another for days now, and she'd left him alone at the precinct to go and change. It was possible he'd heard Castle on the phone making plans with Jacinda tonight and knew that they'd be here. Either way, since he'd failed to return to the bar, she guessed that he was the one who had decided to play matchmaker this evening. His plan was both risky for its logistics and yet simple in its intention. It would be a shame to see his kind gesture squandered.

"Stay?" Kate called out before Castle could get out of range.

When he whipped around to face her, he was frowning. "What did you say?"

Kate indicated the wine. "Stay and have a drink with me? Please?"

"Why, Beckett? Tell me why?"

Kate shrugged, finding herself thrown off-balance by his frosty tone. "It'd be a shame to see a good merlot go to waste," she said somewhat glibly. "And maybe we could talk?" she quickly added when she saw his eyes harden.

The indecision on Castle's face was painful to watch. But Kate forced her tongue to be silent, and she bravely tipped up her chin to stop it from wobbling. The last person she would ever have imagined might reject her was clearly considering doing just that. Her face felt hot and her palms were sweaty, a sickening knot of panic tightened in her gut once more. But then gradually, she watched her partner's features soften just a hair, and she began to breathe more easily.

"Come on. One glass won't hurt," she said, bravely lifting her scarf from the bar stool beside her to allow Castle to sit down.

The writer sighed and seemed to deflate right in front of her. Resignation, hurt and a sense of defeat made him appear smaller than the strong man she was used to having by her side. She missed him - the kind, optimistic partner who had long ago pledged to have her back, the man who made her laugh even when things were at their darkest. This mess they were in was torture, worse than any dangerous scrape they'd tumbled into before, and it was clearly upsetting them both.

"One glass," Castle agreed without enthusiasm, cutting across her thoughts, before quietly adding the caveat, "and then I'm done."

So she had one glass of wine to figure out how to fix this. Challenge accepted, Kate thought to herself as she raised her glass and touched it to the rim of her partner's. "Cheers," they said in unison, one of the few things they had agreed upon of late.

Out on the concourse stood an Englishman, watching this scene unfold. As soon as he saw Castle take the open bar stool beside Kate, Colin Hunt hoisted his bag onto his shoulder, smiled to himself, and then he turned away, quickly heading towards the security line and Gate C47.

No one saw him leave.

Note: This is operaluvr's genius prompt verbatim: I've always wondered what would have happened if Beckett had accepted Hunt's invitation for a drink after their case had closed and they ran into Castle and Jacinda at the airport bar. Or maybe Beckett sitting with Hunt at the airport bar spotted Castle saying goodbye to Jacinda at the boarding gate of her next flight. Or Castle spotting Beckett with Hunt at the airport bar as he says goodbye to Jacinda at her boarding gate. Would either of them be jealous enough to find the courage to speak up and fight for the person they loved most in the world?