Author's Note: After all the research I've done for this fic, I understand why Castle knows so many random facts. Along those lines, while I do have a science background, it's not in the medical field - if there are any mistakes, I apologize. Please feel free to correct me.

Chapter 9

He was wrong. A fact which Kate was all too eager to point out, much to Castle's chagrin.

"Seriously?" he questioned emphatically.

"Her alibi's solid bro," Esposito answered. "Sorry."

"It has to be her," he protested. "There aren't any other connections between our vics."

Kate's phone vibrated against the surface of her desk and she retrieved the device, glanced at the screen before automatically reaching for her jacket.

"Lanie," she offered by way of explanation. "She's got something."

Kate hastened through the door of the morgue, Castle on her heels, caught up in spinning an elaborate tale of lust and jealousy and betrayal that she assumed was somehow meant to disprove Sara's alibi. She wasn't entirely sure. She'd stopped listening a couple minutes back.

"Hey, Lanie. You found something?"

"Cause of death for your second vic." The ME crossed the room as she spoke, collected a folder from her desk. "She was poisoned."

"By what?"

"I collaborated with a couple colleagues of mine from poison control and found compounds consistent with the metabolism of aconite. It's a highly poisonous compound from..."

"Oh, Wolfsbane!" Castle exclaimed. "Right? It's used for pain relief. I researched it once for when Derrick Storm was on a mission in China but I didn't end up using it because..." he abruptly became aware of two sets of eyes fixed on him, trailed off. "Right. Sorry." He nodded to Lanie. "Continue."

"As I was saying," the ME began again, "it's a plant-derived toxin that's also occasionally used as an analgesic. However, its use is uncommon, because ingestion of more than a small amount can be fatal."

"You think she was dosed?"

"According to her medical records, there doesn't seem to be any reason for her to be taking it. Not to mention that it's not commonly prescribed, especially in the US."

"So where would our killer have gotten this?" Kate asked.

"Well, that's hard to say," Lanie began. "Because of its toxicity, it's highly regulated. However, the plant is native to parts of the northern hemisphere, particularly mountainous regions. Anyone with knowledge of plants and a thorough understanding of chemistry could've picked some and extracted the poison."

"And how would it have gotten to Annalise?" Kate questioned.

"I'm guessing it was mixed in with her beer," she answered.

"How nefarious," Castle commented.

"Yes, and fatal," Lanie reminded him. "And," she continued, gesturing with one gloved hand, "I did some research. Initial symptoms include nausea and vomiting, and death presents signs of cardiac and respiratory failure."

"Just like Annalise."

"Mmhmm."

Silence fell as they contemplated this new information, before Kate raised a valid point. "What about Jenna?"

Lanie shook her head. "Test came back negative. I'll run it again just to be sure, but if Jenna was poisoned, it looks like our killer used something different."

"Okay, thanks." Kate turned to go, paused and whirled back around. "Oh, uh, anything else that might connect our two vics."

"I compared their medical records, hospital visits, even places of birth, but there aren't any similarities," Lanie reported. "However, Jenna's medical records aren't complete. There're four years missing."

Castle turned to Kate, index finger extended as he gestured at her. "Didn't Sara mention Jenna lived abroad for four years?"

"Yeah, in South America, though she didn't say where." Kate turned back around to Lanie. "I'll talk to her parents, see if we can get ahold of those. Might give us some insight."

Jenna's parents consented to email the missing medical records which, due to frequent travels, were all already in electronic form. No sooner had Kate hung up the phone than a message appeared in her inbox, a selection of files attached. She opened the first document, scanned it briefly before forwarding the entire message to Lanie. With any luck, it would shed some light.

"Ready to head out?" she asked as she shut down her computer. They'd arrived back at the bullpen just ten minutes ago, and Kate hadn't even bothered taking off her coat. It'd been a long few days and there wasn't a lot more they could do tonight anyway.

When she received no answer, she finally looked up, sought out her husband who was intently focused on the case once again, lips moving slightly as he synthesized the facts at hand with the story that was inevitably forming in his mind. With an adoring shake of her head, Kate tucked the case files under her arm, grabbed their empty coffee mugs, and headed to the break room to rinse them out. She followed up by storing away the case files, stopped to talk to Ryan and Espo on her way back to her desk, giving Castle plenty of time to work through his latest stream of thoughts.

"You onto something?" she asked a few minutes later, coming to stand next to him and nudging his elbow with her own.

"Just trying to figure out the connection," he answered, eyes still glued to the boards.

"Mmmm, yeah," she commiserated.

"Her parents didn't know Annalise?" Castle asked.

Kate shook her head. "Nope. They did have the medical records though. Lanie's gonna take a look at them and let us know."

Castle hummed an answer, clearly preoccupied.

"What?"

"It just doesn't make sense," he muttered, almost to himself. "One vic killed by someone slipping poison into her food, the other potentially poisoned with something... Wait. Poison in her food." Castle echoed his own words, turned excitedly to Kate. "Where's the file on Jenna?"

She opened her mouth, poised to speak, but before she could so much as find the words he was already dashing across the bullpen in a hurry, seemingly not in need of her answer after all.

Okay then.

Apparently they weren't leaving quite yet.

"Everything okay?" Kate asked, passing her husband a glass of red wine before curling onto the sofa next to him. Whatever he'd been onto prior to leaving the precinct, he still refused to divulge more than the fact that he'd had a hunch, and after a few minutes, Kate had simply given up. If it panned out, she'd find out eventually and if not, then it didn't really matter in the end. What mattered was that they found the killer, brought him or her to justice.

But in the meantime, there were more pressing issues at hand.

"Yeah. Why?" Castle answered, searching her eyes.

"I know this case has been tough on you," she murmured.

"No, it's, I mean, yeah. I just can't imagine what their parents must be going through. They had their whole lives ahead of them, and then..." he released a heavy exhale, tilted his head back against the cushions.

"We're gonna figure this out, Castle," she assured him.

"But that doesn't bring them back."

Kate sighed emptily. "No. No it doesn't."

"Sometimes I wish Alexis was still a little girl and I could wrap her up in my arms and protect her from the world," he lamented.

Kate set her glass aside, turned to face him more fully. "Rick," she called softly. When he barely acknowledged her voice, she reached out to cradle his free hand in her own, thumbs tracing gentle lines across the back of his palms. "I know you worry, but this job? This kind of thing? It doesn't happen every day, and it doesn't happen to most people."

"I know, but..."

"Please, Castle," she pleaded. It was times like this that she hated how shadowing her had destroyed his innocence. It was still there. She still saw it at times. But it wasn't the same. He carried these burdens now, too. Burdens he should never have to bear. "It's okay to worry, but please don't let this swallow you up."

He nodded, more to himself than to her, but didn't speak.

"We can make an appointment for Alexis, okay? Just to be safe. Have them run some tests."

He nodded absently but it was a long moment before he broke the silence. "I don't know how you do it."

"I have you by my side," she answered in a low, soothing tone. "I have you to help push away the darkness." She squeezed his hand. "And we have this to come home to."

"But what if...?"

"Don't." Her voice was stronger now, an emphatic appeal. "Don't, Castle."

"She's almost twenty one," he answered, still caught up.

"I know," Kate placated. "But she's a smart girl, Castle. And I can talk to her if you'd like. Give her some advice on what to look for, how to stay safe."

Castle lifted his head. "You'd do that?"

She shrugged as though it wasn't a big deal. "Of course. She's family."

His lips parted, poised to speak, and Kate searched his eyes, raising an eyebrow and leaning her head forward encouragingly as she awaited his words.

He squeezed his lips together, eyes finding hers as he spoke. "You never stop amazing me, you know that?"

Kate dipped her head shyly but couldn't suppress the grin that spread across her face. Castle and his beautiful words.

She worried her lip with her teeth, blinked slowly before flicking her gaze up to his, bright blue and penetrating. "I love you too."

Thoughts?