AN: So, here's my Halloween fic. It's a companion to my other fic "By the Light of the Moon". I highly recommend glimpsing that first before reading this story, otherwise you'll be questioning certain things. Anyway, enjoy!

Disclaimer: I don't own Castle.

Rick huffs as he and Beckett walk to their newest crime scene.

"Come on, Beckett," he whines like a petulant child. "You'd look so hot!"

She narrows her eyes as she shakes her head. "No, Babe."

He pouts, halting his stride when his partner stops. As he looks in front of him, his eyes widen, lips forming into a Cheshire like grin when he realizes it's their scene.

"This is it?" he questions, his tone carrying childlike glee.

"Figured you'd enjoy it," she snickers, walking up the stone steps to meet Lanie near a grave. "So, what have we got?"

The M.E. greets her friend before reciting the details. "Angelica Lewis, fifty-year-old Caucasian female. Time of death about five hours ago. COD unknown, but there's no signs of foul play, so I suspect a heart attack. I'll know more when I take her back to the morgue." The M.E. hands the female detective the victim's license as the author stares at the lifeless form, her blonde hair splayed out, eyes closed, skin grey.

"Maybe she died of fright? It's fitting," Rick comments, earning him a glare from Beckett and a raised eyebrow from Lanie. "What? Look at where we are! Plus, it is the week of Halloween."

His eyes flicker around as if waiting for something to pop out from one of the headstones.

It's one of those small cemeteries that usually sits adjacent to an old church or is stand alone. There's no surrounding gate, so the public is free to come and go as it pleases. The deceased, however…

"Ghosts, Castle? Really?" Beckett snarks, a smile tugging at her lips. "There's no such thing."

"Oh, really?" he teases. "What makes you think there's no paranormal life hanging around here?" He arches an eyebrow earning him a snort.

"Yeah, no."

Before he can argue the high possibilities of the paranormal existing, because he is dating a mermaid after all, Ryan interrupts.

"The gardener is the one who found her. Thought it was a prank at first since it's Halloween week. Obviously, he discovered otherwise." Ryan sighs.

"Okay, well, let's head back to the precinct and see what info we can gather," Beckett announces before heading back to the car.

Once the couple enters the car, Rick starts talking, "Poor guy, must've spooked out of his mind when he realized it wasn't a prank. Speaking of…" he trails off, eyes sliding to his girlfriend.

"No, Castle, I am not "dressing up" as mermaid for Halloween," she grumps, putting air quotes around 'dressing up'. "Besides, how would I get around for your party?"

"We would sort of the details beforehand," he states. Her eyes narrow into slits. "Come on, don't you think it'd be hilarious to fool our friends into thinking your mermaid form is a costume?"

"Nope," she answers, her tone indicating end of discussion. He pouts, turning to his gaze to the window.

He loves Halloween. The costumes, the tricks, the treats, the thrills and chills, all of it. Unfortunately, Beckett isn't as enthralled by it all. He's hoping to remedy that in time for his party on Halloween.

After all, what's cooler than hanging out with an actual mythical being on All Hallows Eve?

Kate stares at the murder board, looking at the picture of their victim. The boys are still looking up on her, so she's waiting for them and Lanie to get back to her. Meanwhile, she feels Castle's stare on her. She turns her head, frowning.

"What's your favorite candy?" he questions. "Wait, scratch that, I know it's gummy bears. You always have a stash on you."

She smiles. They've only been dating for two months, but he knows the smallest things about her such as her favorite candy, shampoo, lipstick, and many other tidbits. It's sweet.

"What's yours?" she asks. She tries to think of what it could be, but he eats a variety of sweets, so she's unable to come up with just one possibility.

"My number one would be Pop Rocks, specifically the cherry flavor one." He waggles his eyebrows, forcing her to restrain yet another eye roll. "I would grab them any time I trick-o-treated."

Her mind briefly wanders to the Halloweens of her childhood full of baking pumpkin shaped cookies and trick-o-treating. Unfortunately, like many things, she grew out of it by the time she hit double digits. A small part of her regrets forcing herself to grow up so fast instead of enjoying life.

"What's making you ask?" she says.

"Just trying to get you into the Halloween spirit," he chirps.

An amused chuckle falls from her lips. She should've expected him to be a Halloween fiend really. Three weeks ago, she had walked in on her partner and Alexis decorating the loft. When she had questioned him, he had responded with "It's never too early for Halloween" while a life size skeleton dangled from his fist.

She had helped decorate, Castle's enthusiasm for the holiday infectious. However, she's still not as crazy about the day as he is, particularly since quite a few cases drop around this time of year.

"Yeah, yeah," she shoots back playfully as Esposito and Ryan approach them.

"Sorry to interrupt your Halloween love fest, but we have information on our vic," Esposito says.

"Address checks out, and it looks like she does have a next of kin, a son, Nicholas," Ryan states, handing Beckett the file.

"Good," she responds. "Castle and I will go visit the son. Why don't you guys start looking around her apartment?"

The boys nod, going off to their task.

"Come on, Castle, let's go."

He follows, standing next to her in the elevator.

Hopefully, this case will come to a quick close.

They stand at the door of the apartment about an hour later, and Castle notices Beckett school her features as she knocks on a door adorned with a large, purple witch hat. He wonders how hard it is for her to give messages like this, and how often does she flash back to the day where she and her father were on the receiving end of such horrible news? All he knows is that's what makes her drive for justice so strong, and why he loves her.

His internal admiration is cut off by the door opening, revealing a young man, probably in his late twenties with his mother's blonde hair.

"Um, hello?" he greets, his green eyes reflecting confusion.

"Nicholas Lewis, I'm Detective Beckett and this is my partner, Richard Castle," she says. "Do you mind if we come in?"

He lets them in, his face a mask of concern.

"Is everything okay, Detective?" he asks.

"Do you mind if we take a seat, Nicholas?" she answers.

Gesturing with one hand for them to sit on a couch, he sits in a leather arm chair across from them.

"So…" he starts, looking between the two of them expectantly.

With that, the news spills from Beckett's lips, her tone as gentle as she can make it.

"But, I talked to her yesterday!" he exclaims, clearly holding back a sob. "We met for coffee last night."

"She died early this morning. Right now, this isn't officially a homicide, so this is more of a formality."

"My mother was a healthy person. Why would she suddenly die of a heart attack?"

"That's what's being investigated right now. Like I said, this is a formality until autopsy results come back," Beckett answers, her voice sympathetic.

Castle glances around, looking at the various pictures hanging on the wall. "Who's the girl in the pictures?"

Nicholas lips turn down into a deep frown. "That's my sister. She and I were close." His green eyes gaze down at his hands, the atmosphere turning even more somber.

"Were?" Beckett quizzes.

"She died of a drug overdose two years ago, and Dad's been out of the picture since I was little, so it's just been Mom and I."

Castle's heart breaks with the realization that the young man is now alone.

"We're very sorry for your loss. We'll be back with an official report. If you need anything, feel free to contact us," Beckett answers, standing to leave.

The two depart, heading back to the car.

"Do you think it was a homicide?" Rick asks. He feels like it could be. While fifty year olds can have heart attacks, the timing and location just seem sketchy.

"I don't know," she says. "I mean, the conditions are off, but it's possible that it was just a heart attack."

He tries, and fights, to hide his smile at the fact that they're always in sync.

A second later, her phone rings.

"Beckett," she answers. After a few hmms she hangs up. "That was Lanie. Apparently, there were some interesting findings on the toxicology screen."

Looks like they might have another case after all.

The duo arrives at the door to the morgue, Lanie ready for them as soon as they cross the threshold.

"What did you find, Lanie?" Beckett asks.

"The toxicology screening showed high amounts of adrenaline in her system when she died," the M.E. states.

"I mean, she was dying, wouldn't that be normal?" Rick questions. Lanie shakes her head.

"Not these levels. Also, there were no wounds found anywhere on the body, or signs of strangulation or anything. So, no physical trauma caused her to have the adrenaline."

"Did she see something, maybe?" Beckett quizzes, eyebrows furrowed.

"That I can't tell you."

After giving the examiner their thanks, the duo returns to the precinct and stares at the murder board.

"Ryan and Espo should be back soon," Beckett states.

"Mmm," Rick hums. "I still think my assumption was correct." He had to be right, there was no other explanation for it.

"What? That she died of fright? Maybe." Her lips purse. "But from what exactly?"

He pouts. "Come on, it is a graveyard," he insists. "The place is probably crawling with paranormal activity!"

"No ghosts," she replies simply.

"How can you say that since-" he starts but cuts off with as she delivers a patent glare.

"Hey guys, we think we found something worthwhile," Ryan chirps as he and Espo approach them.

"Yeah, according to a neighbor, the son and our vic had a huge fight about two days ago. It apparently ended in the door slamming in the son's face."

"Did the neighbor know what the fight was about?" Beckett asks.

"No, just that the same thing happened last year too," Ryan comments. "Same time frame as well."

"Anything happen the year before?" Rick inquires, an idea forming in his head.

"No, not that the neighbor mentioned." Esposito shrugs.

Rick flicks his eyes to Beckett, who understands what he's implying.

"Nicholas said he had a sister, Chloe, who overdosed two years ago. Did she come up on the records for Angelica?" she prompts.

"Uh, hold up." Ryan flips through the file, raising his eyebrows as he reads. "Yep. Chloe Lewis, age 26, died on October 29 two years ago."

Beckett sighs. "I think we need to go back to the cemetery, see if maybe Chloe's grave is there. Come on, Castle, let's go grave hunting."

He does a little fist pump as the boys snicker.

Definitely ghosts.

It doesn't take them long to find the grave.

"Here she is," Kate murmurs, eyeing the stone before scanning the area.

"And it's only a few yards from where her mother died," Castle comments.

She walks over to the spot, looking for anything out of the ordinary, not wanting to succumb to Castle's suggestion of ghoulish activity. She might be a mermaid, but that doesn't mean every other mythical being exists.

However, as they search, they come up empty and she's almost close to admitting he's right. Almost.

"So, what the hell happened?" she murmurs. Looking around one last time, she notices something glinting in between Chloe's grave and the stone in back of it. Pulling it out, she finds it's a locket, with pictures of Chloe, Nicholas, and Angelica.

"Huh, why is that here?" Castle asks.

"Perhaps Nicholas might know," she remarks. "Let's go pay him another visit."

Twenty minutes later, they're at Nicholas' door, Kate knocking on it.

A moment later it opens, revealing Nicholas' wary face.

"Is there something I can help you with, Detective?" he asks as he ushers them inside.

Kate produces the necklace and flecks of recognition enter the man's eyes.

"My sister's locket!" he exclaims. "Where did you find it?"

"Behind Chloe's grave," Castle answers. "Do you know how it got there?"

The young man shakes his head. "No, Mom must've-" he trails off, traces of disbelief in his voice. "I don't know why Mom would have left it there. She refused to visit Chloe's grave with me the other night."

"Was that what your argument about the other day?" she presses. "A neighbor said you guys were pretty loud."

Nicholas hangs his head. "Yeah, it was. Mom pretty much disowned Chloe once she got into drugs. I tried last year and this year to get her to come with me on the anniversary of Chloe's death, but Mom said no, saying she didn't see any reason to mourn someone who was already dead to her." His tone is bitter, angry. "Our meeting for coffee the other night was to make up. We did, sort of."

Rick arches an eyebrow, catching on to the exception. "Sort of?"

A small sigh falls from the man's lips. "We begrudgingly agreed that we would cope with Chloe's death the way that we felt suitable to ourselves. Though, I don't see how her way is actually coping. Seems more like not ignoring instead of mourning anything."

Kate shoots him an empathetic gaze, understanding the unhealthiness of certain coping mechanisms.

"Maybe she was just lost," she supplies gently.

"Yeah, well, she'd definitely lost something, her empathy." Nicholas turns his attention toward a photo of the three of them on the mantel. "If you don't mind, I would like to be alone."

"Of course," Castle murmurs, and the duo leaves, shutting the door behind them.

"Definitely not him," Kate states, shaking her head.

"Definitely," he agrees.

She releases a deep sigh, realizing they have little to go on.

Now what?

That night, they sit in the bath, both unsatisfied with the day's events.

"So, what could've killed her?" Kate murmurs, the tips of her tail trailing the edge of the tub. "And don't say a ghost." She pokes Castle's bicep from behind her, causing him to chuckle.

"Then it was probably just a poorly timed heart attack. Then again, there's no right time for a heart attack." He wraps his arms around her as she nuzzles his neck.

"Yes," she mumbles against his skin.

He thinks for a moment, deciding to throw an idea out there.

"Maybe we should visit the graveyard again, except at night."

"Castle, there's no-"

"I'm not talking about ghosts. But what if there's something going on in that graveyard?" They both know it's not the craziest idea he's had. "My last proposal turned out to be correct," he points out.

"Yeah," she grumbles, a smile tugging at her lips.

"So, why not try?" he begs, placing a kiss on her neck, trying to soften her up.

"Not fair," she grouses, melting into him. "You know I'm too easily influenced."

"And I use it to my advantage." They both chuckle, knowing full well he doesn't and wouldn't dare try to control her, soulmate or not. "Let's go tomorrow night."

"Fine," she concedes, lifting herself out of the tub and drying herself off, returning to her human form.

Castle lifts himself out and she takes a moment to ogle as he dries himself off.

"See something you like?" he teases.

Instead of answering, she presses herself against him, wrapping her arms around his neck.

"Take me to bed," she murmurs.

"Yes, ma'am."