He wouldn't see her that evening and it felt like a sting to his heart.

Just how exactly his 48hr romance could turn into such a deep metaphysical connection, such an overwhelming need to be with her still eluded him.

And yet, there they were, sharing what little free time there was between her television appearances and his job on the force, living in comfortable oblivion of whatever was happening here, whatever was developing between them in this timeless dream, free from the restraints of reality.

Two more days Allison would be in New York before she would appear on several talk shows on the west coast, that much she'd told him early on. What would happen in those two days, and the days thereafter, that was a different issue he'd been unwilling to address.

The implications of the public spectacle that could surround this relationship were massive, yet he'd chosen to ignore that too, following his heart only when it came to this matter.

Four days of bliss would be worth the pain in the end- or so he told himself.

Finishing the last sip of cold coffee, he slowly rose from his chair, stretching the tight muscles in his body courtesy of the last few hours spent sitting hunched over, going through their case from beginning to end. It had kept him away from home, away from the nagging feeling that came up whenever some free time made him long for her.

No, the more he kept himself busy, the better.

But 10pm had come and gone and whether he liked it or not, the next morning would be here soon enough and some sleep in between was the best he could offer his body.

Mostly alone except for a couple other detectives and the start of the cleaning crew, he reached for his leather jacket, ready to head home when he almost ran into an anxious Castle.

Breathing heavy, the writer held a stack of paperwork pressed against his chest, his eyes wide in excitement as he circled Esposito to head to the murder board.

"Castle, what are you doing here?"

"I think I got it, Espo. Not everything…but I got a start. And we've been wrong from the beginning. This isn't just some run-of-the-mill lunatic. That's not him at all."

Intrigued by the evident case break, Esposito followed him to the board, where he watched the writer's hand move along the timeline near the bottom, then stare at the crime scene photos intently, slowing down here and there before he nodded affirmatively.

"Yes. That's it. It's perfect."

Esposito frowned, but remained still otherwise, knowing from past experiences that it would be best to let Castle finish his train of thought, wrap his mind around the matter before any questions could be posed.

Several moments later, his patience would be rewarded when Castle turned to face him, a victorious smile on his face.

"I know what he is doing now. Not why, but what. That guy's a copycat."

With his brows raised, Esposito approached the board, unable to see the connection Castle had drawn despite his best intentions.

"Impersonating who?"

"Another killer, who else?", the writer replied matter-of-factly and began to disassemble the stack of paperwork he'd brought along, carefully spreading it out on Beckett's desk, "See, I just couldn't make sense out of all the sudden body drops, the moving of the corpse, the mutilation. It's like we're dealing with different personalities here, different killers. The entire time we were looking at these bodies, I felt like they didn't belong. And then I realized that our killer staged them to replicate a murder spree from forty years ago."

"From…what? What are you talking about, Castle?"

Too tired to sum up the patience needed to deal with the brilliant writer's flowery set-up, Esposito reached for some of the paperwork, trying to make sense of the information provided. Castle stopped him midway, pointing a finger at his chest to push him back.

"Forty years ago, a Michigan man killed seven women in a matter of three years, all in the same brutal fashion and all but one in close proximity. The youngest one was only thirteen, the oldest 23. He always dumped the body away from the murder site and returned several more times to visit his victims. When police came across the bodies, they were partially decomposed, with the first victim missing both feet, her thumb and index finger on her left arm, most of her right arm missing completely, just like Raquelle. Now this guy is in prison now, but I am willing to bet, whoever is…is following in his footsteps is doing so to a tee."

The disturbing news made Esposito hesitate, then look over at the murder board, comparing the innocent faces of his victims to the state their body had been found in.

Following his glance, Castle drew in a shuddered breath, then pointed at the timeline below.

"The original killer struck only once in July of '67, then once in July of '68, however, he killed five victims in a matter of four months in '69, greatly accelerating his pace. So that means if this guy changed his timeline from years to days…"

"It's possible we're about to come across five more victims soon."

Frozen in his spot, Esposito let the information sink in, barely acknowledging Castle when he relayed a discussion he'd had with an old State Police buddy in Michigan who'd in turn helped add some detail to the information gathered.

While he stood there, the writer added a printout of seven black-and-white photos to the board, highlighting the time of death along with a dated map of where the bodies had been dropped.

"Sounds like we should have a discussion with this killer and find out who he's been talking to. Maybe he's trying to relive the old days vicariously."

"Already done.", Castle added confidently, "Well, not literally. But John Norman Collins won't talk about the murders. To this date he denies any involvement. Police were only ever able to pin him to one of the murders and even that was based solely on circumstantial evidence. As far as Collins is concerned, he had no involvement in any of it."

"I don't know. If you ask me, that'd be an even greater chill; continuing the killings he still denies. I think we better go through all his phone calls and letters first thing in the mor-."

In the middle of the sentence, Esposito stopped in his tracks, letting his eyes drift back over at Castle who had returned his attention to the murder board, as if to seek the answers amongst the massive amount of data.

"Wait a minute. Where…where's Beckett? Did you tell her already? I mean, you came all the way here…"

As if the question was confusing, Castle looked back over at him, his eyes strangely distant.

"I…I guess I didn't."

"What do you mean you didn't? You two are always coming up with the case breaks, the… ehm…the give and take, the completing each other's sentence. You mean to tell me you came all the way over here to share your progress, but you never even called her yet?"

For the first time since his boisterous entrance, Castle completely stood still, his gaze drifting to Beckett's desk, studying something there that only he could see.

"Hey, what about you? What are you doing here at…at ten at night? Don't you have someone to flirt with to get over Lanie? A new flame perhaps? Someone who could take the salt out of the wound?"

Esposito hadn't expected the turn of questions and glanced over at the writer awkwardly, unable to deny that he'd been caught off guard. Eventually, with a heavy sigh, he cocked his chin at the desk phone nearby.

"You know, how about you just call Beckett and stop asking questions. She needs to know what's going on with this case."