A/N: "This is heavy" and "Great Scott" are exclamations repeated by the main characters in the movie Back to the Future, which was mentioned in the previous chapter.

Also, I'm SOOOO sorry for the super long hiatus, I did NaNoWriMo and couldn't write through November, and then it was hard to start this up again, and I was busy… anyway, here's the long-awaited return of the story!

"It merely looked like the Earth and occupied the same coordinates in space-time." – Mostly Harmless, by Douglas Adams

Castle had, in a surprising act of helpfulness, dug a story-planning whiteboard out of his office, wiped it clean, and set it up in his living room. Beckett took two of his kitchen magnets and posted pictures of Basher's body and the crime scene that she'd taken with her phone and printed out. The sharp smell of the Expo marker as she wrote Alan's name at the top of the board was comfortingly familiar.

"Just like the murder board," she smiled, standing back to admire it.

"The what board?"

"Never mind." Kate capped the marker and set it on the silver tray at the bottom of the board before resuming her contemplative position a couple of feet away from the board. Evidence and theories were spinning around in her mind, and this too was comfortingly familiar. "So, I'm pretty confident that it actually was Dick Coonan that killed Alan Basher," she said. She turned to face Castle as she filled him in on everything she'd figured out. He was standing in the middle of his family room with a somewhat dazed expression on his face. "Thing is, Coonan's a hired killer, so there's still someone out there who wanted Basher dead and contacted Coonan to make it happen."

"Whoa," said Castle, "this is heavy," earning himself an odd glance from Beckett. "Sorry," he explained, "ever since you brought of Back to the Future I've had lines and quotes from it running around my mind." She nodded, trying not to smile. This was Castle, alright, albeit an alternate version of him.

"I'm not sure if it would be helpful to go arrest Coonan and see what we can get out of him," she mused. "I don't know if he'd break."

"You don't know him well enough from your… uh, 'alternate reality'?" he replied.

"I killed him before we could get to talking," she answered. He wasn't quite sure what to say to that, so he joined her in perusing the board.

There was a long list of things Kate Beckett wanted. She wanted Castle to make morbidly funny remarks rather than wincing at the bloody autopsy picture. She wanted the help of Ryan, Esposito, and Lanie. She wanted to figure out what the hell was going on. She wanted her cop-self back, but she didn't want to lose what she had here: her mother. Montgomery. An apparent past relationship with Castle.

Stop. An instant mind-block went up inside of her. That last thought hadn't belonged there, and she wondered if it was a side-effect of being immersed in an alternate universe that had caused the unbidden idea to pop into her mind. That wasn't something she wanted, and it wasn't something she couldn't bear to lose. She'd be glad to return to her normal relationship with Castle.

She really didn't have enough time or brainpower to focus on solving the murder, getting back to her own world, and her confusing feelings for her partner. She pushed the Castle issues to the back of her mind and concentrated on the picture she was staring at: Alan Basher and the stab wounds on his abdomen and chest. Alan Basher, the ex-boyfriend she didn't remember.

For whatever reason, she began to wonder why and how they'd broken up. She wondered what the circumstances were, wondered if it had been messy. Her stomach filled with ice and she stumbled back onto the couch. "Oh, God…"

"What?" said Castle, hurrying to her side. "What is it?"

"Castle, what if it's me?" Her eyes were wide, searching, vulnerable, and she couldn't stop her hands from shaking. "What if I'm the one who told Coonan to kill Alan?"

"Well… why would you do that?" he said slowly, completely lost as to how to act. He wasn't sure of what she wanted to be convinced.

"I don't know, but I don't even know who I am," she said. "I'm not the person I think I am. I'm a drug-addicted moral-less actress who sleeps around. Maybe I also order people to be killed? I don't know!" Her eyes flicked upward like the answers were on the ceiling.

"Kate, look at me," said Castle. She did. "I don't think you killed Alan Basher." He didn't really think that- he didn't really know what to think. He just wanted her to calm down. "Although I'm sure that if you did, you had a very good reason." He got a small laugh out of her.

"Thanks," she murmured, catching the time on the cable box. "Whoa, is it already ten?"

"Is it?" he said. "My daughter's supposed to be getting back from her date around now."

"With Ashley?" Beckett tested.

"Yeah."

"Good kid." He didn't bother asking how she knew that, and she appreciated it. They were finally slipping into some sort of pattern, some variety of understanding. She instructed him to keep the murder board facing a wall in his office and grabbed her bag. As she turned to leave, though, a thought occurred to her. A thought entirely unrelated to the murder, but still intriguing.

"Castle," said Beckett. "Kiss me." He reacted like she'd just asked if he would travel to Pluto with her. "I have to see if it's the same. Just pretend like we're undercover as a couple."

"Okay." He said it nervously, but nevertheless stepped forward and pulled her to him. They kissed.

She'd fully intended to keep that other kiss, the one in her own universe, in mind as she kissed Castle. She had planned to evaluate this one and compare it to the other one. As soon as the kiss began, though, this proved impossible because she couldn't focus on anything but the feel of him and the passion in the kiss.

They broke away from each other, a bit out of breath. Castle appeared speechless. It was an experiment, Beckett thought to herself. Nothing more. An experiment.

"Well, goodnight," she said, her voice unnaturally high. "See you tomorrow." She hurried out the door and shut it behind her, taking several deep breaths to calm herself. Alone in the hall, she leaned against one of the walls and rocked her head back to stare at the ceiling. Her heart was thumping too quickly.

"Great Scott."