Title: A Matter of Time
Rating: PG-13/T
Originally posted: 14th August 2018
Originally written for: debirlfan
Notes: for AU Exchange 2018 on Dreamwidth and AO3.

Sheldon appreciated the irony that Penny was the first to figure it out. After all, she was the least likely choice on the surface, having the lowest IQ of any of his so-called friends and associates. Still, he had come to realise over time that Penny possessed something even more valuable in some ways than the supposed intelligence of homo sapiens, or even the supreme intelligence of homo novus. She both understood and cared deeply for her fellow humans.

"How did you know?" he asked her, intrigued to hear the specific answer.

Penny smiled and sat down on the couch cushion next to his own specific spot.

"I didn't, not at the start," she admitted. "I mean, when we first met, I knew you were smart. Even smarter than Leonard" she said with a smile. "All that Beautiful Mind stuff, that's possible for regular people. Not a lot of people, but still. I don't know, Sheldon, you're just... different. You're like nobody I ever met before and in way too many ways that didn't altogether add up. So, I figured you're either from another planet or from another time. When you made such a big deal about all your string theory stuff I did a little research. You know me, I have no clue what any of that sciency stuff really means, but string theory is the thing that could allow people to travel through time. A lot of things suddenly started to make sense after that."

"You really do pay attention," said Sheldon, nodding his head in understanding. "It's so strange that all the people I have known these last few years, one of which I have actually shared an apartment with, never realised the truth. Leonard just thinks I have 'issues'," he air-quoted and then rolled his eyes for good measure. "For such things, he really should look closer to home."

"Ain't that the truth?" Penny laughed, unable to help it. She stopped abruptly as she looked at Sheldon shifting awkwardly in his spot. "I can't believe this. I mean, I do believe it but... you're really from the future. That should be impossible, right?"

"It's improbable, from your perspective at least, but certainly not impossible, obviously."

Sheldon got up from his seat and paced a little. Penny wasn't sure what to make of his uncomfortable movements. She had felt pretty stupid coming over here to talk about her theory on whatever secret Sheldon was hiding. It seemed obvious to her that there was something. Leonard told her a few things but none were significant enough, none of them explained all the parts that didn't make sense, until now.

"You know, I won't tell anyone, if that's what you're afraid of," she told him then.

"Penny." Sheldon sighed tiredly then. "Fear is something from which homo novus does not suffer. My only concern is that you will compromise yourself in one of your drunken stupors by telling the world my secret and inadvertently having yourself locked up for your own protection and that of others."

As was usual for Penny, she had a take a moment to translate from Sheldon to English.

"Seriously, does everybody talk like you in the future?"

"It's speak like me, and yes, most of the new race are extremely articulate," he explained, "but that is beside the point," the continued, literally waving away her concern as he returned to his seat. "I would rather not have your being locked in a padded cell on my conscience, so please, for your sake, do not divulge my secret to anyone."

"Aww, sweetie," she said, getting an expression on her face that Sheldon could only called 'googly eyes.' "You really care that much what happens to me?"

"I do," he admitted, glancing away. "It's strange. As I said, I have known Leonard a great deal longer, and Wolowitz and Koothrappali almost as long. There are doctors at the university and neighbours in the building that have known me for many years but I can stand the thought of leaving them all behind to return home when the time comes. It is you, Penny, that I feel I will miss the most."

His hand on her arm was almost more of a shock than the words he had said. Sheldon would miss her when he left. That was very sweet, but the over riding message she got from all that he said was that he would be gone someday, potentially soon.

"Sheldon..."

"You have a lot of questions" he cut in before she could say more. "I understand. In fact, I was prepared for this very situation occurring, though the materials I had for such an occasion are really more geared towards those with a basic understanding on the principles of physics. There really are no cattle roping analogies that are going to cut it when explaining the complexities of time travel and the version of the future from which I have come."

Sheldon genuinely hoped he had not offended Penny. Where, or rather when, he came from, speech was so much more literal. He did not understand sarcasm because it simply did not exist in the future. In many ways, for all the advancements in technology and such, the future was a simpler place, or more correctly, a simpler time. That said, most of the people of the future had a much greater understanding of science, even those who were not experts in such fields as time travel. It could be explained to anyone with a rudimentary education in the future, but here and now, things were very different.

"Stick to the basics, Sheldon," Penny advised. "I've seen the movies and the TV shows, at least, some of them. Is there a magic phone booth or a car you have to drive past 88 or what?"

"Nothing so interesting, sadly." Sheldon smiled. "No, the actual process is quite boring really. One simply steps into the booth in one time and steps out in another. I could explain the exact scientific process involved in the transportation but as we've already established, it would mean very little to a waitress from the Cheesecake Factory."

"I'm gonna let you have that one, sweetie," she said, patting his arm.

Penny could choose to take offence but there really wouldn't be any point. She definitely would not be able to wrap her head around anything involving molecules, atoms, string theory, black holes, or whatever other scientific craziness Sheldon tried to tell her about. She understood the concept and was content just knowing that time travel was a thing and it was essentially achieved as it was in the movies. Step into the time machine, step out again. All the stuff in-between really didn't matter at all.

The fact that Sheldon's whole life here was essentially a lie blew her mind, especially when she let herself think about it for more than a minute.

"You have a family," she said suddenly, frowning hard, she was sure on that. "A mother, a twin sister!" she pointed out.

"Simple implanted memories," said Sheldon, waving away her concerns one more time. "The Cooper family believes I was a part of their lives, and I learnt my part well enough to behave as if I were."

"But... you must have a real family, in the future?"

"It's an outdated concept five hundred years from now."

"Five hundred?!" Penny gasped, getting to her feet by pure force of shock. "Sheldon, you're... you're from five hundred years in the future?"

"Naturally," he agreed, nodding his head. "While it is true that technology in this time is developing at an alarming rate, it will still take the evolution of mankind to the next level before he ever truly learns the secrets of time travel."

"So then, here's the part I really don't get," said Penny, shaking her head. "Why are you here? I mean, I'm glad you're here but of all the times and places why here and now? Why Pasadena in 2008?"

"Well, when I came here it was 2000 and the location is the very same longitude and latitude in both points in time."

Penny frowned hard.

"Hold on a second. The time machine that brought you here... landed here?" she checked, pointing at the couch on which she was sat.

"Precisely in this spot. My spot," he said pointedly.

"Woah!"

Her head was spinning. Penny was amazed she hadn't completely lost consciousness from some kind of brain overload with all this crazy information. She fully understood why Sheldon worried about the authorities locking her in some mental facility if she ever talked about this whole time travel thing. It sounded insane, beyond belief, and yet she believed it. She believed him. Of all people, Penny never doubted she could trust Sheldon Cooper, even though his whole life was technically a lie. The irony of that was not lost on her.

"Penny," he said, reaching for her hand.

It was only when he failed to make contact that she realised she had stood up and backed up a step too.

"I'm sorry," she stammered out. "I just... It's a lot, Sheldon."

"I know," he agreed. "You asked why I came to this time and place? It was purely experimental. Subjects had previously gone back ten, twenty, even up to fifty years, but the further back one travels, the more risk is taken. I was the one who did the math, double-checked the equations, and trusted my work enough to test the theory that travelling back more than a century was possible."

"You travelled five centuries," said Penny, wondering when her voice got so soft. "You didn't know what you would find."

"History told us approximately what would be here. The level of evolution, the technology, even the food. Of course, the nature of people, their individual personalities, that we couldn't know. What I mean to say is, I could never have anticipated you, Penny."

It was all weirdly romantic, she thought, as Sheldon looked at her in a way no guy ever had before. She really meant something to him. Maybe just a good friend and confidante, maybe more. Either way, Penny was flattered and then just a little sad.

"Wow," she said softly. "I finally meet the most incredible guy, who is genuinely something so special and amazing, and there's absolutely no way we have a future... because that's where he's from," she said, smiling sadly.

"When he's from," Sheldon correctly gently, standing up in front of her. "Penny, I... I don't have to go back. There's no way for anyone to make that choice but me and... and I confess, I hardly think I'll be missed in my own time. Not as I might be missed here if I did go back."

"Forward," she told him, laughing even as a tear streaked down her face. "You can't go back to the future... unless you're Michael J. Fox," she considered, swallowing hard.

He smirked at her almost-joke. They did not share much by way of pop culture references. In fact, they had very little in common on paper, but that didn't matter so much. Sheldon had read about the relationships between men and women in the past and had experienced them by proxy as his friends attempted to date with various levels of success and failure, but he never had thought this would happen to him. That he would come to feel so much for someone like her, it had seemed impossible, and yet.

"You'd stay for me?" she asked then, looking up to meet his eyes.

"I could," he told her, nodding his head. "This life is mediocre in so many ways, but I can excel here. I am far more intelligent than my fellow man and for as long as I continue to be mindful of germs I may not be immune to and learn more about the correct social behaviours of the homo sapiens, I believe I could live in some semblance of happiness in this time... if I did not have to do it alone."

Penny had no words to give him after such a speech. Everything he said was so weirdly beautiful and every part explained so much about who he was. She never thought that Sheldon Cooper could mean more to her than he had before, but somehow, he was managing it today.

"You do know that you will have to keep my secret forever, whether I stay or go, and that... that any relationship between us may never be of the fullest kind that I know you have enjoyed with other men-"

"I don't want any other man," she promised him. "I understand now," she said, her hand reaching up to touch his cheek. "All the quirks, the weird habits, it all makes so much sense. This isn't your time. You're just trying to fit in, fighting to hold on to all your secrets, making sure you don't catch some disease that could kill you because they don't have it in your time. I get it now, and I get why you couldn't tell anyone, but I am glad for everything you've told me now."

"I am also glad that you figured it out. From the first day, I hoped you would," he told her with a smile.

When she moved to kiss him, unable to keep from doing so any longer, Penny wondered if he would let her. Up to now, even a hug sent him running for the hills, but things had changed today, in the past hour or so since she walked in the door and confronted Sheldon with what she believed to be the truth about him. Now she knew for sure, and when they kissed, she was sure of something else too. She was in love with a time travelling man and, crazy or not, she had a feeling they might just make each other very happy as they went ahead and built their own version of the future together.