Sherlock had been studying Caroline from the moment they met. For the past two weeks, she felt like she didn't have a single second of peace. He watched her constantly. Asked her questions. Questioned her when she ate food. Asked for samples of her blood. Observed her while she drank blood. Caroline needed a place to stay in London but she wasn't sure it was worth all of this.

She was sitting at her laptop, trying to figure out the latest news of home, when Sherlock entered the room. "Caroline today I thought we might—"

"No!" She shouted, a bit more loudly than she probably should have. It was enough. She had had enough. She wouldn't be his play thing any longer.

"Pardon?" Sherlock replied, taken aback at her outburst.

"I'm not doing this anymore. Being your science experiment. I'm a person, not a lab rat!"

"You aren't a person you're a vampire."

Caroline glared at him and let out a violent groan. She stood up off the couch and grabbed her jacket stomping toward the door. She nearly knocked John over as she flew out in frustration. John turned and looked at her and then continued inside, shutting the door behind him. He glanced over at Sherlock, who quickly looked away, and went into the kitchen.

"What was that about?" John asked, settling into his easy chair with his morning tea.

"Apparently Caroline objects to my experiments on her," Sherlock said opening the refridgerator and removing a small vial.

"Well too right. She's a person Sherlock not a lab rat."

"She's not a person she's a vampire."

John rolled his eyes and groaned. "Please don't tell me you said that. Out loud. To her." When Sherlock didn't respond, John knew he had hit the mark.

"Sherlock, I know I say this all the time. But you've got to switch it off," John said. As always Sherlock continued about whatever it was that he was doing, but John knew that he was listening. "Caroline may be this exciting new thing for you to amuse yourself with, but she she is still a being with feelings. At the heart of it she's a lost girl, in an unknown city, we don't even know why she's here."

"Pass me that slide would you," Sherlock said holding out his hand.

John sighed and walked over to the kitchen counter to pass him the microscope slide. "We should find out more about her. Every time she even mentions her home, she gets sad. There's something going on with her."

Sherlock stopped and looked up at John, who was now lost in thought. John was better at the emotional side of things. It wasn't Sherlock's area.

"Maybe we should just send her off," Sherlock said.

Maybe it was time. There wasn't any reason for Caroline to stick around. She had money, Sherlock knew that from simple observation. Somehow her excursion in London was being funded. The girl went shopping frequently enough that it was clear she wasn't on any sort of budget. She would be fine on her own. And she could protect herself. She was a vampire. She had super strength and abilities. He realized that John had been speaking the entire time, probably chastising him for even suggesting the idea, but he was resolved. Caroline was clearly an unsolvable mystery and one that he didn't intend to waste time on any longer. The decision was made.

It late in the evening. Sherlock sat alone in his flat. John had gone out on some date or something, Sherlock couldn't remember. It had been hours ago that Caroline had left. She hadn't texted or called. Maybe she had left for good. Maybe Sherlock would be spared any need of kicking her out so to speak. He wasn't kicking her out though. The current situation just wasn't working . Yes he had brought her here, but it was an experiment, and it wasn't going well. She was never meant to become a permanent fixture in their lives.

Just then, the door to the flat opened and Caroline walked through. She looked down awkardly as Sherlock's eyes met hers. She shut the door and walked over to the couch, sitting down slowly, assuming the same position she had been in this morning.

"Walked around Trafalger I see," Sherlock said.

Caroline laughed slightly and rolled her eyes. She had no idea how he would know that, but it was something she was getting used to. Although that entire day she had been that she wasn't sure she should be getting used to him. Making allowances for the fact that clearly Sherlock was socially deranged. In the two weeks she had been living with him she learned that he was rude and blunt and too smart for his own good. He rarely listened and sometimes wouldn't speak for hours and really didn't seem to care about much of anything. Except maybe just proving that he was smarter than anyone else in existance. She wasn't sure she could be friends with someone like that. Someone who didn't connect with anyone or feel anything. Someone who was such a robot.

"Caroline, I'm not sure this…experiment…is working out," Sherlock said.

"I agree," she replied.

"I look at the facts and—"

"Being a vampire isn't just about facts Sherlock. Its emotions," Caroline said interuppting him. She wasn't really sure where those words came from.

Sherlock scoffed. "Emotions just get in the way."

Caroline gave him a tiny smile. "You sound like a vampire sometimes."

"What do you mean?"

Caroline thought back to the vampires she had met throughout her life. At one time or another every single one had said those words to her. It was so unusal to hear them coming out of the mouth of a human. But then again it was Sherlock. Maybe it made perfect sense.

"When you're a vampire, you're emotions are heightened. You feel everything so quickly and strongly its difficult to keep track. That's why sometimes vampires just switch it off."

Sherlock cocked his head at her. "Switch it off?"

"There emotions," Caroline explained, "Its called the humanity switch. But sometimes I don't think it really exists."

"Why not?"

Caroline looked at him very seriously then, her blue-gray eyes piercing his. "Because eventually you still feel the pain and guilt of being a monster. The feelings creep their way in. Its impossible to be emotionless forever."

Sherlock let her words sink in. Humanity switch. He smirked to himself. Caroline raised a brow at his reaction.

"What?"

"John is always telling me to switch off," Sherlock said.

"Well I say maybe you need to switch on," she said staring at him head on.

Sherlock looked at the girl sitting before him. She was a total enigma to him. The more he spoke with her, the more he learned about her, the more intrigued he became. And this humanity switch she spoke of. He realized he couldn't let her go. Not yet. His instincts told him not yet.

He remembered earlier when John had said that they didn't know much about her. Sherlock knew some things. The things he observed from their first meeting. But it all stopped there. His eyes scanned her face, her hair, her hands, her clothes all for clues about her past. But he came up with nothing. He didn't know why she had left America and come to London. He didn't know if she had friends or a family or anything. Something about her look told him she was alone in the world. It was a look he recognized.

Caroline cleared her throat and leaned back. Sherlock realized that he had been staring at her for quite some time. Longer than appropriate. He straightened up and leaned away from her.

"No more experiments then," Sherlock said.
"Is that a promise?"
Sherlock smirked at her and laid back on the couch, his hands behind his head. He had a lot to think about.