A/N: Okay, sorry for dropping off the face of the earth. Again. It wasn't exactly a planned break from fanfiction, but I'm back regardless. Thank you everyone who is continuing to read this story. You guys amaze me. Thanks also to those of you who have reviewed!

Jason was silent in the back of her Charger as they drove back through the maze of streets to return to the precinct. Even Castle was quiet, occasionally flicking a glance her way as if there was something he wanted to say only to purse his lips and then return to leaning to the side of the car where he could get a glimpse of how much traffic was idle in front of them.

"Is it safe for me to leave the hotel?"

Surprised, Kate lifted her eyes to look at Jason via the rear-view mirror.

"If I thought that there was even the slightest chance that Johnny T was behind this, Jason-"

"-Jason, Beckett's the best at what she does," Castle interrupted, maintaining a steady gaze on his wife rather than twist to look into the back. "She wouldn't ever knowingly put your life at risk." Kate shot him a grateful smile in the few seconds she could afford to look away from the street as traffic began moving again.

"So what happens now then?"

It was easy to detect Jason's fear guiding his questions, so Kate kept her response as simple and reassuring as she could. "We're just going back to the precinct so we can show you a few pictures."

"Okay," Kate said as she breezed into the interview room with the relevant case file. Opening the file, she proceeded to lay out its contents on the table, placing each photograph so that Jason could easily see the faces. "Do you know any of these people? Do any of them look familiar? Just take your time, Jason."

On the table top was a picture of every 3XK victim they knew about, including mugshots of Marcus Gates and Paul McCardle.

"Did Carrie know any of these people?"

"I don't think so," Jason answered hesitantly. None of the blonde women staring back at him looked like his girlfriend's colleagues or friends, but it was hard to be completely sure. And he didn't think he'd ever seen either of the two men whose pictures were on the table. "You should talk to her office though – they might have seen one of these people there."

Kate nodded, but at that moment in time it wasn't likely she would follow his suggestion. They had no evidence other than the staging of the crime scene that indicated the involvement of Jerry Tyson. And they were still waiting on Lanie's autopsy results to know for sure if the rope used to strangle Carrie was indeed the same types used in the Triple Killer murders. Showing Jason the pictures was supposed to reassure Castle. If the task doubled up as checking for a connection between their victim and the previous murders, so be it.

"What about this photo?" Beckett asked, pulling the only remaining mugshot from the folder to show Jason.

"That's him, isn't it? 3XK? I recognise him from the news."

Kate nodded. "You haven't ever seen him outside yours or Carrie's apartments?" Jason shook his head. "Have you had any workmen in either building recently? Cable guys, plumbers, anyone like that?"

"I don't think so, but I'm not at the building most of the day. I leave at half five every morning and I was only ever at Carrie's building late evening, so if there were any workers in her building or mine, I would probably have missed them."

"Do the buildings have logs for visitors?" Castle asked.

"Carrie's does, but mine doesn't."

Kate sighed. If Jason's apartment building had had a sign-in sheet, they could have maybe found their murderer that way.

"Okay, I think that's it for now-" No soon had she spoken than her cell phone began to trill, vibrating in her pocket. Pulling it out, Kate read the number for the ME's office. "Sorry, I just need to take this. Castle, could you take Jason to the breakroom for now?" As soon as they were gone, she answered. "Lanie?"

"I've got the autopsy report. You wanna come down to see me?"

"Sure, give twenty minutes," Kate replied, checking her watch as she hung up before stepping into the adjoining observation room where she knew Ryan and Esposito were probably waiting.

"Lanie finished the autopsy?" Espo asked.

"Yeah, I'm just gonna head down to see her. You two okay to go get a copy of that visitors' log from Carrie's building?"

"You got it."

"Thanks, guys."

Before leaving, Kate dropped in on Castle to tell him where she was going and ask, maybe fluttering her eye lashes once or twice, if he could just babysit Jason for a while. Once he'd grudgingly agreed, receiving a quick press of her lips to his in thanks, she was on her way, rhythmically tapping her fingers against her thigh as she stood in the elevator and waited for it to take her down to the underground car par.

"So what have you got for me, Lanie? Please tell me, you found evidence that refutes Castle 3XK theory."

"Sorry, no can do, girl. I spent four hours analysing the ligature marks on her neck and the fibres I pulled from the body. She was strangled with a three-strand twisted quarter inch rope. It was green and white-"

"-Nylon?"

Lanie nodded apologetically. "Sorry, Kate, it looks like Tyson really is your killer."

"Could still be a copycat," she argued.

"None of these details were ever released to the public, were they?" It was a question that Lanie already knew the answer to, a question she only asked to make a point.

"So maybe he told someone – like he did with Marcus Gates," Kate suggested. She knew from experience that psychopaths like Tyson enjoyed telling people about their violent acts, that reliving the experience brought them almost as much gratification as committing the crimes themselves did.

Lanie raised a disbelieving eyebrow, but kept silent.

"Is there anything else you can tell me about the murder?"

"Time of death was three pm. Other than the rope fibres and the tiniest traces of denim under her fingernails, there's no other evidence."

"The denim under her fingernails-"

"-Probably from struggling with the killer," Lanie replied, nodding as she finished Kate's sentence. "Unfortunately, there's nothing unusual about it. It's a standard blend of cotton and elastic. I've been working with lab technicians to recreate the murder. Our current theory is that our guy pinned Carrie down with his legs while he strangled her on the couch, explaining these slight impressions on her arms."

Kate nodded, examining the marks on Carrie's biceps for herself. There was definitely an indent that could only have been formed by the inner seam of a pair of jeans.

"Two of the lab technicians have been programming the scene into a computer to see if we can get any more details about the murder – height, how much force he'd have needed to be able to strangle Carrie like that-"

"-It's definitely a man?"

"We don't have the evidence yet," Lanie conceded, "but most likely."

"Hey, sorry I was gone so long – traffic jam on Park."

"Don't worry about it," Castle replied, waving her off and squeezing her hand to draw her attention again. "Coffee?"

"Please." Shooting him a smile, Kate shrugged off her coat, leaving the tan wool hanging over her chair before following him into the breakroom, where she was surprised to see Jason still sitting on one of the sofas. The fact that she'd forgotten she'd left him with her husband made her feel guilty.

"So what did Lanie say?"

"Hmm?" Blinking away her distracted gaze, she twisted to face Castle, watching him expertly froth the milk for her latte.

"What did Lanie say?"

"Oh," Kate said, glancing at Jason before telling him, "I'll tell you later." Receiving her coffee, Kate took a grateful sip, trying to keep her moan of pleasure to herself. Judging from the smirk on her husband's face, however, she wasn't exactly successful. "I'm just gonna go and update the murder board. Have the boys come back yet?"

"Nope," he said, walking out of the room behind her. He sat in his chair beside her desk while she wrote the definitive time of death and the other information Lanie had given her on the whiteboard, drawing a timeline along the bottom. So far they only had a few events on it – Carrie's text to Jason, her death, the first discovery of the body when Jason got in from work and the second discovery the next morning when one of the neighbours saw the open door. It wasn't a lot, but it was a start.

"Green and white nylon-"

"-Castle, I know what you're thinking-"

"Yo," Espo called as he stepped off the elevator, interrupting what Beckett was about to say. "Got that list from Carrie's building, as well as CCTV footage from a corner shop across the street."

"I thought we could put a face to every name and then check CCTV around Jason's building to see if any of them crop up."

"Good idea," Kate told Ryan, accepting the logbook the Irish detective was offering her. Her quick glance down the list of names from the previous week didn't put up any red flags. Handing it back she asked, "Get Tori to help?"

Ryan nodded, taking the two video tapes and the book he'd returned with to the tech girl. He was shut in the room beside the breakroom, printing out pictures of each person who stopped off at the apartment building, then checking the timestamps to find a name for each of the faces.

Out in the bullpen, Kate was doing what she was best at – building theory with Castle, while Esposito went through a copy of the list of names in the logbook with Jason.

"Kate, the green and white rope-"

"- I know," she murmured. "But she wasn't killed in her own apartment. Whoever killed her knew she was going to be at Jason's apartment."

"So they followed her?"

"Or she told them where she was going. If she was followed, it should be on the CCTV footage that Ryan's been collating. We just have to track whatever route she went to find out."

"But that would suggest she was friends with whoever killed her," Rick argued.

"Maybe she was." Kate shrugged. "Carrie doesn't have any defensive injuries. The only sign that she struggled at all is the denim under her fingernails." Checking her father's watch, she sighed at the time – it was almost five o'clock and they'd yet to make any real traction with the case.

"So why would one of her friends want to kill her?"

"Guess we'll have to speak to some of them tomorrow to find out. Maybe one of them will know what this surprise she had for Jason was. Maybe one of them was involved in the surprise and that's why they needed to kill Carrie."

"That doesn't explain the whole 3XK feel though…"

"Look at it this way, Castle," Kate said, reaching across the table to take his hand, "if Tyson was back, don't you think there'd have been another body by now. His MO was killing three women-"

"-Yeah, in a week," he countered. "It's been three days, he's still got time."

The words had no sooner left his mouth than Kate's cell phone began to ring, the vibrations carrying it across the surface of the desk between them. They both stared, watching its progress for the smallest of moments before Kate reached out and picked it up, swiping her thumb hesitantly to answer the call.

"Beckett?"

"Body at Amsterdam Avenue for you."

Sticking her head around the door, Kate watched Ryan and Tori working, two different streams of video running side by side on the same screen, for a moment before interrupting. "How's it going?"

"We've put faces to names for about a third of the list. The assumption is that people not on the list are residents, but if they're not…" Tori trailed off. She didn't have to tell either Ryan or Beckett that their murderer could escape detection that way.

"Well, keep at it. Have you managed to track Carrie's route from her apartment to Jason's?"

"We've got her on camera leaving her apartment at 1:08 pm," Ryan answered, "and managed to track her as far as the subway on Cathedral but haven't got her coming out on 18th street near Jason's apartment-"

"-Maybe she got off early if she thought someone was following her," Kate suggested but Ryan was already nodding.

"I've already sent out a request to have the footage sent over."

"Tori, do you think you can manage to keep going through this by yourself? We've got another body," she explained, shooting both of the others an apologetic look. Had she not just received that call from dispatch, they would all have likely been able to head home in an hour or two. With a second murder – one that was presumably linked to Carrie Richard's death, if the fact it had been assigned to her was anything to go by – they probably wouldn't leave the precinct before nine o'clock. The scene and any nearby possible witnesses would have to be canvassed immediately, and even if she wasn't stuck there she'd probably still have to stay at the precinct to begin profiling the victim and getting in touch with the next of kin.

Ryan looked to Tori as she replied, "Sure, it's possible I can cut down the time it'll take by running a facial recognition program."

"Great, thanks."

After grabbing Ryan, Beckett sent him on ahead with Esposito to help secure the scene. Before she and Castle could join them, they had to drop Jason somewhere. As his apartment was still a crime scene, he had to check into a hotel, and taking him to the one of his choice was the least they could do after quizzing him all day. Once she promised to keep him informed and up-to-date on the case, they were on their way, pulling up outside a nondescript apartment building behind Lincoln Square which had uniformed officers swarming outside.

"It's on the eighth floor," one of them muttered as she walked forward, briefly flashing her badge at them just in case.

"Thanks."

Taking the elevator up, the two of them were quiet and mindful of the other occupants. But despite that, they were both well aware of what the other wanted to say.

The eighth floor was as busy with cops as the street entrance to the building had been, but Beckett ignored them and the neighbours they were talking to, instead walking straight past and through the open door marked with police tape. She and Castle froze in the doorway.

"Happy to call it Tyson's work now?" he asked, staring at the blonde woman lying supine beside the coffee table with her hands folded over her middle.

A/N: So let me know what you thought of the chapter. The story is going to be quite case-centric again for the next few chapters at least, but as before I'll be doing my best to run a few of my storylines side by side. Sorry again for taking forever to write this chapter and put it up and thank you for sticking with me if you're still reading.