Chapter 10

The tender silence was promptly interrupted by a key in the door, and Castle and Kate's heads automatically swiveled towards the source of the sound. The lock clicked, followed by the turning of the doorknob, and the door opened to reveal a swirl of long red hair as a young woman stepped across the threshold, shutting the door behind her.

"Alexis?"

His daughter smiled, dropping her purse onto the floor and unbuttoning her black and grey plaid pea coat. She wore heeled black boots over form-fitting dark wash jeans, and a deep green sweater that beautifully complemented the color of her hair.

"Hey."

"Everything okay?"

She shrugged, draped her jacket over the arm of the sofa. "You seemed upset the other day and I just thought..."

Castle stood without preamble as Alexis approached, wrapped her up in a crushing hug, and he could feel a weight lift from his shoulders, some of the anxiety of recent days rolling off of him.

"Are you sure you're okay?" Alexis asked as he loosened his grip, perceptive eyes searching his face.

"You would tell me if something was wrong, right? If you were in trouble or out drinking and..."

"Dad..."

"Or if someone..."

"Dad," she interrupted more firmly. "I'm only twenty, remember?"

"I know, but..."

She stepped back, folded her arms defiantly. "Is this about the case?"

Castle opened his mouth to reply, closed it again when no words escaped.

"Whatever happened...that's not me," his daughter iterated. "I'm careful."

"I'm sure they thought they were being careful too," he voiced. "And now they're dead."

"Dad..."

"Castle," Kate murmured in his ear, resting a gentle hand on his shoulder as she stepped up behind him. He startled slightly, hadn't even heard her approach. "Could you give us a minute?"

He took a moment to compose himself before nodding, backing away and leaving them alone to chat. "Right, of course."

Kate waited until he'd crossed to his office, disappeared from view, before sinking into the sofa and gesturing for Alexis to make herself comfortable.

"Is Dad okay?" the girl asked worriedly.

Kate sighed. "The case we're working right now – the victims are two girls not much older than you."

"That's awful. What happened?"

"Well we're still figuring that out," she relayed. "But they presumably got tied up in something. Something bad."

"And Dad's worried I might end up in the same situation?" she profiled accurately, stubbornly crossing her arms over her chest. "Because he doesn't trust me."

"No, Alexis, he trusts you," Kate promised. Things had been rocky for a while but over the last few months they'd managed to repair most of the damage, resuming their original close relationship. Nevertheless, Castle's overprotective tendencies were not to be quashed, nor was Alexis's ever-growing independence. It was a battle that neither was destined to win. "But things happen, sometimes unintentionally. And you're a beautiful, intelligent young woman."

"Yeah but..."

"I know you know how to stand up for yourself," Kate continued, holding up a hand to prevent a protest. "And I know you have a solid head on your shoulders. But he's your dad, Alexis, and he has a writer's imagination." Alexis rolled her eyes knowingly. "He's always gonna worry, and there are times where he'll be annoyingly protective. My dad was the same way when I was younger."

"So what am I supposed to do?"

"Keep your head on straight and always be aware of what's going on around you," Kate suggested. "Surround yourself with people who are the same. And just remember that he means well. And he loves you."

Alexis seemed to relax at that, relenting a bit of her stubborn defiance. "I know."

The conversation dissolved into a variety of other topics from there, Kate asking about school, Alexis animatedly relaying a story from one of her classes and recounting an interesting guest lecture she'd attended the previous evening.

As their easy back-and-forth came to a natural pause a few minutes later, Alexis stood, shifted to straighten her sweater.

Kate nodded in the direction of the office. "You should go talk to him."

Alexis offered an assenting smile. "I will. Thanks, Kate."

She shrugged as though it wasn't a big deal. After all, Castle was her husband, and though she wasn't much of a mother figure, Alexis was technically her step-daughter. They were family. "Not a problem."

"No really," the girl pressed. "I'm glad he has you."

Kate smiled broadly, heart overflowing with love. "I'm lucky to have him too, Alexis."

"So I ran some more tests, like you suggested," Lanie offered first thing the next morning as they strode into the morgue, coffee cups in hand.

Kate furrowed her brow in confusion. "I didn't sugge..."

"Not you." She nodded to Kate, then to Castle. "Him. And I think he might be onto something."

Ah. That explained what he'd been up to yesterday.

Castle grinned smugly. "See, I told you..."

Lanie held up a hand, halting his proud declaration. "Let me finish. I ran a variety of blood tests, and this time something popped." She opened a folder, passed it to Beckett. "I found higher than normal levels of IgE. It wasn't a lot, but it was enough to raise a red flag."

"IgE?" Kate repeated, brow furrowed.

"It's a type of antibody. Part of the body's immune response," Lanie explained. "It's typically elevated in people with allergies, particularly following an allergic reaction."

Kate dipped her head in confusion. "You think she had an allergy attack?"

"This along with the low blood pressure and edema around her airways," Lanie listed. "My guess is that your vic went into anaphylactic shock."

"And what could have triggered that?"

"Medication, insect stings..."

"I doubt she was stung by an insect at the bar," Castle interrupted.

"Food allergies," Lanie continued with a nod in Castle's direction.

"So her death could have been accidental?" Kate asked.

"I ran some additional tests just to be sure," Lanie continued. "Along with the vodka martinis she'd been drinking, it appears she'd also ingested small amounts of peanut oil."

Kate furrowed her brow. "That's not an ingredient in any martini I've ever heard of."

"Not to mention an odd method of consuming peanut oil," Castle mused.

Lanie nodded in agreement. "I checked it against those missing medical records you sent me. She was diagnosed with a peanut allergy at age eleven, after a severe reaction landed her in a hospital in Peru."

"So you think she was murdered?" Kate pieced together.

"I think that's the most likely scenario."

"So someone doses her drink with peanut oil," Castle began. "Enough to set off the reaction but not enough for her to taste it."

Kate took a step closer. "After a few minutes, she realizes what's happening..."

"And that's when she panics and runs out," Castle recollected.

"Mmm, someone with a food allergy would've had an Epipen," Lanie interrupted.

"Maybe she didn't have one with her," Castle suggested.

"No, Lanie's right. She wouldn't have gone out without one," Kate mused.

"Maybe she couldn't find it."

"Then why not call 911?"

He shrugged. "Maybe she panicked."

"Or maybe," Kate began, advancing one more step, eyes lighting up as the pieces fell together in her mind, "she did have one when she left the house, but..."

"Her stolen purse!" they exclaimed in unison.

Kate's eyes eagerly searched her partner's face, found his eyes twinkling back at her, that familiar spark of excitement from their crime-solving banter.

Lanie crossed her arms over her chest, cleared her throat pointedly, and the partners jerked apart, hastily putting some space between them.

Kate snuck a glance at her friend, found Lanie regarding them with a raised eyebrow, her lips curved into an amused smile. The detective stepped back, pressing her lips together in embarrassment.

"Shut up."

Thoughts?