AN: Sorry about the unannounced absence; I got hit with a TSUNAMI of school work and a work opportunity I couldn't pass up.

It wasn't until he had teleported into Snowdin that Sans began to have second thoughts. After all, he and Gaster hadn't exactly left on the best terms. Plus there was the issue of why he'd been called here; the scientist had said he'd only call him on reset-related business, and Sans had since sworn off anything to do with time.

He hesitated outside the town, debating. But eventually, curiosity won out. After all, he could always decline, right? He'd just…check things out.

He walked into the sleepy town, giving a few waves to the townsfolk that recognized him. Why would they go to Snowdin of all places? After patrolling it for the past few months, Sans could guarantee that this was the least exciting town in the Underground. Good for patrolling, yes, but it couldn't be that great for science. He kept a socket open for anything out of the ordinary, but it wasn't until he reached the large house on the edge of town that he saw the tall, thin figure waving an arm. Gaster was positively grinning at him; that was…weird, especially after everything that had happened the last time they'd spoken. The scientist quickly walked up to meet him.

"Sans! Forgive me, I should have specified the location, but I am so glad you are here!"

Sans couldn't help chuckling; it'd been a long time since he'd seen Gaster so happy.

"Nice to see you, too, Gaster," he said, then glanced up at the house. His browbone furrowed slightly, and he pulled up his hands to sign, "What with house?"

Gaster looked at Sans quizzically, then mimicked the signs before shaking his head with a half-smile. "You are very much out of practice," he said, then turned and looked up at the house. "It is quite…er, much, is it not? Asgore insisted on something, er, roomy, I think is the word? But it is much too big for my tastes."

Sans blinked. This was Gaster's house? He must have passed it a hundred times by now. He glanced up at the other skeleton. "Y'know, I think it'd look better with some Christmas lights."

Gaster laughed. "And who would turn them on? I often spend my nights in the lab." He shook his head. "But this all is unimportant. Let us get out of the cold." He set a hand on Sans' shoulder and guided him into the house. Sans wasted no time in looking around; it certainly was roomy—much bigger than his and Papyrus' place in the Core—but…really empty. Gaster gestured to a nearby sofa, where a yellow dinosaur was sipping from a mug.

"Sans, this is my assistant, Alphys."

"We've already…" Oh, wait. Different timeline. "Uh, nice to meet you." He held out his hand for Alphys to shake. Alphys jumped up and took it with a sweaty palm, nearly spilling her tea.

"Hi! I'm A—wait, sorry, Gaster just said that." She gave him a pained smile. "Um, sorry I wasn't out there. I, erm, I don't do so well with the cold. Yo-you know, being, erm, cold-blooded. O-only physically, though! Not…oh, god, this is terrible."

"Hey, hey, don't worry," Sans assured, then winked. "Listen, when you're in Snowdin, you just gotta chill."

Alphys blinked, then gave a little snort. "Oh my god, that's awful!"

"It's only gonna get worse. I'm aw-full of 'em."

She snorted again, and Sans chuckled as well as he sat down beside her. He looked up as Gaster re-entered the room, setting a steaming mug in front of the smaller skeleton. Sans looked up at him. "So, uh, why the note?"

Gaster grinned. "I made a discovery several months ago. You see, this house, though far too big, has the most fortuitous location." He pulled a small slip of paper out of his pocket, holding it up for Sans to see. Sans' brow furrowed as he took it.

"It's the picture of the research group," he said, brow furrowing more as he realized he couldn't name a single monster.

"Yes, yes. Now, look at this one."

Gaster handed Sans another photo. It was the same picture, but only half the group was in it.

"What?"

"You see, just below us is a room. Initially, I did not think anything of it and merely kept it as a storage room. But then I saw this picture among my notes. It remained unchanged, as you can see." Gaster's hands were whirring in his excitement. "After the, er, incident with Terrin, I brought down the second photo, to see if it was affected as well, and as you can see, it is frozen as well despite subsequent resets and, er, disappearances."

Sans leaned forward, brow furrowed. "So…you're saying your basement is outside of time?"

"Yes! Well, at least, that is how it appears. I did some research upon realizing this; apparently there are rumors of a door in Waterfall that occasionally appears…" He shook his head. "I will be brief. Essentially, I have theorized that there are several of these 'grey rooms' throughout the Underground, but the one beneath my house appears to be the only one that is static!"

Sans leaned back. "And what does that have to do with 'making history'?"

Gaster grinned again. "If we have a place unaffected by resets, then that means we can work without fear of it all being erased." He shook his head, pacing excitedly as his hands flew too quickly for Sans to translate. "I have had an idea for a while, but it has been impossible to pursue what with the potential of a reset occurring. But if the work can remain undisturbed, just as these pictures were, then that means that we can…that we can…" He blinked quickly, trying to find the words.

"We're gonna build a time machine!" Alphys blurted.

"A what?!"

Gaster nodded eagerly. "Yes! We know that resetting is dangerous for monsters. We are far too fragile to do it on our own without devastating side effects. But if we could use a machine to transport us across timelines, it would lessen the strain on our bodies."

Sans' brow furrowed, and he looked back down at the pictures. "This is impossible."

"Erm, not…not entirely," Alphys said. "I-I mean, there's no guarantee that it would work. But…in theory…the machine would act as, um, as a container? Kind of? For a monster's dust. So…so they wouldn't lose as much."

"This is why we need you," Gaster said, meeting Sans' sockets, still grinning. "You are, for all intents and purposes, the leading expert on resets. You know what equations work and which theories are true. Your experience makes you much more knowledgeable than myself. And with Alphys' talent with mechanics…"

Alphys quickly shook her head, bright red. "It's not…I mean, it's just…"

"You do not need to be modest," Gaster said with a fond smile, then turned back to Sans. "You are familiar with the robot Mettaton?"

Sans chuckled. "He's all my brother watches."

Gaster proudly motioned to Alphys. "And here you are with his creator."

"Wait, really?"

Alphys had managed to turn a brighter shade of red. "He…uh…well, I mean…I-I did make him…"

"Huh. Well, that's…riveting."

Alphys covered her face with an awkward giggle. Gaster clapped his hands together.

"So! Are you willing to join?" the other skeleton asked, sockets bright.

Sans shifted in his seat. "Uh…well, I'll be honest. My last reset didn't leave me in great shape." He gestured to his permanent grin. "So, uh, I'm a little hesitant to do anything involving resets."

Gaster shook his head. "There will be no physical resetting, I promise you that. Simply equations until we can test the machine, which will not be for some time."

Alphys, fanning her face to cool it down, added, "That's true. It's…well, I mean, what we've guessed is that we'll be able to enter the equation into a program, and the machine will do the actual reset."

Sans looked between the two of them, brow furrowed. It was still a risky move. Time wasn't something you could just play with. But…if it was just equations…then he didn't have much to worry about until they built the actual machine. And, truth be told, he'd missed working in the lab and all the research. Plus it was right where he and Papyrus patrolled…

He leaned back on the sofa. "So when do we start?"

Getting back into the scientific routine was…outrageously satisfying. The equations, the discussions…with all the stress and worry from the past few months, Sans had forgotten how much he genuinely enjoyed doing research. And Alphys—once she'd been coaxed out of her shell—was good company. Sure, she was a little…okay, she was really nerdy, but they spent plenty of time talking and joking between the grey room and the lab as they sorted out the time machine. It was like…well, what he imagined the research group must have been like. Except with a lot more gushing about anime.

Even with her obsession with big-eyed cat girls, there was no denying Alphys was a genius. After an idle comment that they should find a way to test shifting the equations into a program, she managed to put together a working machine to gauge shifts in the timeline.

"I-I mean, it's still really crude, a-and it's probably not guaranteed to work," Alphys said sheepishly as she showed the little machine to Sans. "But it's really no—"

"Okay, no, I'm gonna stop you right there," Sans interrupted. "This is amazing. We've needed something like this for ages, and you just whipped it up like nothing? You're definitely super cool."

Alphys went bright red and fidgeted. "Uh, um…thanks? I mean! God, I'm sorry, I don't take compliments well!"

Sans chuckled as he gathered up his notes. "Then how do you put up with Gaster? All I've heard about you is compliments."

Alphys managed an embarrassed smile. "He, uh, he tends to write them down. Then I don't have to react in the moment." She turned to fiddle a bit with the machine, then glanced back at Sans. "Hey, so…you, um, I mean, I heard you weren't really into science before the whole, um, reset thing."

Sans shook his head as he started making corrections. "Nope. More of a beat-'em-up kind of guy." He winked. "Then I got lazy."

Alphys smiled. "So, um, how do you know Gaster, then? If-If that's not too personal! But, erm, you know, he's kind of…reclusive? So…y'know…"

Sans looked up at her. Should he tell her the whole story? Well, probably not the Judge part—she was already so nervous, she'd probably dissolve right there if she knew what his real job was. He leaned back in his chair. "Well, uh, I live in the Core and do some…free-lance stuff for Asgore. So I'd heard people talk about him. And everyone knows where the Lab is, so when I felt like something was off, I figured he was the best person to go to." He shrugged. "And the rest you know about."

"Oh, okay." She shook her head. "I thought you were, like, his nephew or something."

"Do you think all skeletons are related? Alphys, I'm offended," Sans teased.

"Oh my god! No! I'm sorry! I mean, there's the way he talks about you and you both do the hand signs, so I just thought…oh, god, I'm being skeletonist. Is that the word? Oh, god…"

Sans laughed. "Easy, Alph, it was just a joke. I asked him to teach me his language to, uh, get back to my roots, even though…well, it's all complicated. But I'm still pretty bad at it, mainly because I'm too lazy to practice." His brow furrowed. "Wait, you said he talks about me?"

Alphys nodded as she grabbed a wrench to fix a bit of the machine. "Well, yeah. I mean, it was mainly when you guys were doing the research, but he kept talking about all the theories you came up with and how exciting it was. So I thought, 'oh, he's a proud uncle' or something. But! That's dumb of me! Because you can talk about people all the time without being related to them! I mean, I talk about Undyne all the time and we're not related!"

Sans nodded, half-listening. Huh. He shouldn't have been surprised, really; it was just talk about theories.

Still…

Even with the issues over the past few months…

He couldn't say it wasn't nice to hear.