Looking back on it, Sans also knew the exact moment his life started turning to shit. Now it's been many more years of machines and tests than without them, trying to unlock how and why he's different. The core had taken a lot longer than expected, but mind you he'd spent a fair amount of time where he'd gone out of his way to be unhelpful. That or unforeseen incidents setting back progress. He still saw papyrus regularly, which helped him soothe his nerves somewhat, but he'd quickly gone from the lab being an exciting treat to hating it there. Very quickly. Life wasn't too hard, really, he lived here less like a prisoner and more like a permanent hospital patient. And there was Alph, and thinking about her as he stood waiting for his moment almost made him change his mind. He would just have to hope she would understand. No, the real problem had always been his father being away long enough or him leaving cams unattended long enough for him to get out - especially after he had moved to the capital. But… something had gone wrong and everyone had been called for an impromptu emergency meeting under the sound of alarms and sensing his moment after years of patience, he... pretty much just strolled out through one of his shortcuts while everyone was distracted.

But where to go? Retrospective moment over, he refocuses. He had poured over the map he'd kept of Alphys' trying to memorise the layout of all the places he'd only heard about, and even this was risky. He go home, because they didn't live there anymore and he needed some… time away from his father. He realised with a sad twisting in his soul that by proxy that meant he couldn't see Papyrus either, but he also knew that if anyone was likely to blow his cover, it would be Pap. Nor could he trust any of his dad's followers for help, as he'd dubbed the assistants. They admired and clung onto him too hard, he'd be dropped in it in a second. The hood on his hoodie comes up as he steps onto the street. Maybe he could ask Asgore for help? He knew he and his father were close, but he was also a complete softy and he was pretty sure he wouldn't have known about the tests. Which also brings up the question… what had dad told people about why he was suddenly one son short? He didn't think his dad was so stupid he wouldn't have said anything, but it would be good if he knew what had been said so he knew what he would be up against if he did run into any questions from anyone.

Asgore was probably his best bet for now. Him or… of course.

It's not long before he steps into the bar, as warm as he remembered it to be. He's kind of grateful for that, pink slippers feeling soggy from the snow. He quietly makes his way through the busy and chatting crowd towards the bar, and sits on the bar stool whilst keeping his hood up and head down. The living flame comes across to take his order and he sticks his hand in his pocket to take out- he left without any gold. Well, anything he'd bought had been stuck on the expenses form whether his dad was aware or not. Shit. He goes to leave, but a glass of milk and plate of fries appears before him anyway.
"i… uhh… i haven't…"
"You look hungry… start a tab." Grillby replies.
The duck near the bar starts to translate and Sans holds up a hand. "got it, thanks."
He's got half a mind to turn and leave, but his hunger demands he stays and eats where he'd left so suddenly and hadn't had time to think about things like that… so he stays and eats. A small stream of food and drink keep him here until the place is empty, and Sans hadn't even noticed how late it was getting until the place fell quiet. The door softly locked, and panicked mode engaged.
"i'm sorry, i shouldn't have… i'll pay you back… i should be going-"
"Sans." Of course Grillby knew who he was the whole time. If he had a stomach, it would have just bottomed out from a mix of relief and panic intermingling.
"…you didn't tell him i was here, did you? gaster, i mean."
"I haven't seen him since he moved with Papyrus to go to the capital to be closer to you." Sans has to chuckle at that, and it's humourless. If he had eyebrows, Grillby would raise one. "...that is why he moved? You've been sick for a long time."
So that's what he's been saying is it?
"well, i do feel pretty bone tired." Grillby gives a quiet chuckle at that, and it cheers Sans up somewhat. "but… i haven't... i mean, i'm feeling better."
"And you're here?"
"eh, i needed some time out."
"Let me rephrase my question. Sans. Why did you come here looking exhausted and hungry and all but panic when you thought I might have told your father you were here?"

He pauses, wondering how to actually answer that question. He decides to go for as truthful as he can bear without going into details. Besides, as much as he hates going through all the tests, Gaster's still his father and he doesn't really want him to get into any trouble. "i've been inside a long time, ...recovering, and i'm not going to turn to dust having a few days out. he might want to take me back with him soon as he finds out I checked myself out. you know yourself what a bonehead he can be."
Grillby chuckles, although he's not sounding convinced. "There's a bed in the spare room if you want it. Fuku's in hotlands studying so you shouldn't be bothered."
"...thanks, grillbz." He smiles, feeling a little bad about not telling the whole truth. He'll stay a day or two, and move on. He doesn't want to take advantage of the good will.

So, naturally, Grillby somehow managed to convince him to still be in the apartment above the bar three weeks later. They fell into a comfortable routine quickly and after the fourth day, Sans had taken to helping before hours and cleaning up after everyone had left so he was at least pulling his weight. He supposed Grillby enjoyed it partially because it was almost like when he and paps used to visit regularly, and partially because it meant he had some company after Fuku had left him in an empty house around the bar being open. It was weird though, he had expected at least some questions being asked around by people to see where he was by now. Hmm.
"I brought a bottle up after I finished cleaning."
"what? oh, sorry. i lost track of time." He drags his eyes away from the window. "how boned am I right now?"
Grillby offers a small laugh. "Well, considering that you were the one who insisted, I think I can let you take a night off." He comes and sits by him on the unmade bed, handing him the bottle of scotch that looks… red? Sans shoots him a questioning look. Grillby shrugs. "Pre-mixed. You think I don't notice the scotch going missing when you're having a bad night when you've only asked for the ketchup?"
Sans flushes as much as a skeleton can, rubbing the back of his head in shame. "uhh… sorry."
"It's already on the tab." Grillby nudges him, and they both share a chuckle.
"so what makes you think i'm having a bad night?" He asks, taking a few long swallows.
"The fact that since you woke up this afternoon, I haven't seen anything of you. Usually a good indicator."
"hehe, no pulling the wool over your fry-s is there?" He grins.
"No smoke without fire, Sans." Sans laughs. "You know me. I'm not going to push it, but I'm here if you want an ear."
"you don't have ears."
"Nor do you." He takes the offered bottle, and dubiously sips it. He hands it back, glad he lacks facial expressions. "I'll… let you finish that off."

Grillby's said what he needs to say, so he leaves for now. He's not surprised when Sans ends up following him out to the lounge two hours later, swaying slightly. He has a feeling more than one bottle might be missing from downstairs as well.

"so… do you think… he's even looking?" Sans flops onto the couch, head landing in Grillby's lap. Grillby sees a flash of memory where the skeleton spent many days where their father had worked late with no warning, with his head like this as he was worrying. He'd been a lot smaller then, though.
"I honestly don't know enough to be able to tell you, Sans." Grillby's flames fizzed with some concern, but Sans doesn't seem to notice. "You showed up after nearly thirty years after your father told us you were staying in the lab because you'd fallen ill. I think most of us assumed… well, assumed the worst. Well, up until he moved, that was enough to give us some hope."
"hehe, yeah." The laugh holds no humour. "'ill', right. the worst thing about my health was always being bonely. there was always someone around, sure, but they were always there as an observer. 'scientific detachment'. hehehe, i threw my arm at the last person to tell me that. one of his minions. just 'i got a scientific detachment for ya' and woop- arm in their face." He laughs, this time it was definitely amused, and Grillby found it impossible not to laugh along with him, despite the highly disturbing implications of where this conversation was leading.
"Sans?" He waits for the laughter to pass. "Did he-"
Sans cuts him off with a clumsy hand to the face. "shh." He looks and giggles. "whoops, forgot you don't have lips. how do you talk anyway? or eat?"
"How do you?" A note of irritation colours his tone, and it seems to refocus the very drunk skeleton. The hand is removed from his head flame. Thankfully.
"i don't think the word is… the one about to come from your… face... fire... thing. they're more like… tests. tests and tests and tests and tests. tests until i literally can't do anything but sleep, sometimes." It definitely sounds like the word he was stopped from saying. Concern starts fizzling through his flames again and this time Sans does notice. "he didn't hurt me, actually he tried his best to treat me well even when i was being an asshole, but i don't know… i became a puzzle to solve, i think. and the less he got answers and the older i got, the more it frustrated him. and you know what he's like when he can't solve a problem."
"Sounds like you did the right thing walking out, honestly."
"but it's not him." Sans sighs from his lap, sad eyes betraying the frozen grin.
"... Papyrus." Grillby clicks. It was never his father he was asking about in the first place.
"the one good thing was his visits. Well, him and alph but it's not the same. anyway, pap used to catch me up on all the cool stuff he was doing and it was his visits that kept me… well, sane. and if he was visiting, there was no tests. And i thought by now that i would have heard someone talking about a skeleton looking for his brother, but…"
"I can find out. For now, I would try not to worry about it." Sans gives him a lazy thumbs up.
"sounds good grillbz."
"But for now… you should get some rest." sans shrugs in his lap.
"...aren't you even a little bit curious? you got little ol' drunk me full of secrets and an empty skull."
"Well... you are exactly the same as you've always been even, when you were younger. You'll say what's on your mind whenever it takes your fancy. I didn't get to being an old flame by being impatient."
"oh. well, then, thanks." Sans sighs again, and promptly passes out on his lap, but Grillby can't bring himself to being upset. He checks Sans is asleep before shifting himself out from under him and standing to go and use the phone without waking him.

The routine is picked up the next morning as if nothing was said the night before. Routine is nice, Sans thinks to himself as he's wiping tables down. Better than he gave it credit for, maybe.

Sans had only one thing that he'd planned from the outset, and she hadn't been hard to find. Actually, Asgore's little protégé hadn't been hard to find at all - it was just that he'd needed to pull his shit together first. That, and roam the underground until he knew it nearly as well as he knew the lab. He'd watched silently and unseen as Undyne and Asgore trained, and as they headed in from the gardens to drink tea together. It was strange, from Papyrus' stories he's built her up to be cruel and cold, but she appeared to be anything but seeing her without a front to put out. The soul doesn't lie though, and there are marks there that denotes her violent streak. She seemed to value strength, but it was the wrong kind of strength. He figured that she just needed a little help to be shown how to see how strong his little brother was.

Undyne's leaving through the twilight hall when she walks chest-first into a solid mass. She stumbles back a few steps having been taken completely off guard, and is surprised to see a skeleton there. He was shorter than the dweeb she was used to dealing with, and despite the grin on his face and the fact he's stood with his hands in his pockets, something about him made her skin crawl uncomfortably.
"Oh, great, another dweeb. Get the fuck outta my way, I'm too busy to waste time with you."
"hope you don't speak to my brother with that mouth."
"The really tall nerd? You're related to that guy?" He sees it on her face. Then she laughs, some thought going through her head amuses her. Sans figures it's probably the complete lack of physical resemblance - she wouldn't be the first to find it amusing or strange.
"i'll take that as a yes." Now he's staring at her, and that mixed with the smile that hasn't moved an inch she just wants to get out.
"Whatever." She strides past him. As she reaches the end of the hall, however, he's stood there waiting for her. Same stance, same look. She looks between the space where he had stood and where he stood now. "what the hell?"
"i'm here to give you some friendly advice."
"Save it."
"No, you really want to hear this." She notices that the voice changes for a moment, and it commands her attention. Then he's back to his lazy drawl, and Undyne has no idea what the hell is happening but she really doesn't like it. "see now, my brother's been telling me for a while now that you're being kinda mean to him. he's come to you a few times to make friends, and i'm pretty sure the last time that i spoke to him, you shoved him. it was a little while ago, you might not remember, but i do - same as I remember you didn't hurt him, but you hurt his feelings really badly."
"Then maybe you should be telling him to leave me alone. I don't make friends with wimpy losers like him, if he wants to be friends maybe he should grow up and stop with the touchy-feely stuff."
He just stares at her. "he's not a wimpy loser, you just don't know him... or you don't know what strength is. one of the two."
"I know enough about him to know he ain't worth my time."
"so what about when you're in the royal guard? aren't they supposed to protect 'wimpy losers' like him once asgore's finished training you? looked like you're pretty close." Undyne's eye twitches. A smirk lights his pupils. "yeah, i was watching."
"Why do I attract the freaks?" She mutters to herself. "You want me to leave him alone? Fine."
"mmm… i was just going to ask for that, but then you started being an asshole. so. instead, i'm gonna make you a deal."
"what?" She all but hisses the word at him. This little punk's really starting to get on her nerves. Who does he think he is?!
"you spend a day with him. you indulge him in whatever weird thing he wants to do, you smile and you play along and you play nice. you don't have to be friends after if you don't want to be, but you give him a chance."
"No wa-"
"or..." He cuts her off firmly. "we can continue this discussion a little less friendly-like. It's your choice, pal."
She stares at him, trying to figure out what the hell he thinks he's playing at. Anger bubbles within her. She *CHECKS him, and laughs when she sees 1HP "and what if I take option 2, punk? You aren't going to be much of a fight. I nearly kicked Asgore's BUTT!"
"then you obviously option 1 is the bigger challenge, if you can't stand him that much."
"CHALLENGE? HANGING OUT WITH THE DORK AIN'T A CHALLENGE! YOU WAIT AND SEE! FUHUHUHUHUHU" He lets her storm past him this time, satisfied.

One day is all it's gonna take, he's sure of it. It's impossible not to like Pap once you spend time with him.

Papyrus stared at his phone, wishing it would just ring already. He was very happy that his brother had finally managed to get outside but he just wished that he hadn't been forgotten about. "NO, HE HASN'T FORGOTTEN ABOUT ME. HE COULDN'T, I AM FAR TOO GREAT. HE DIDN'T HAVE A PHONE WHEN HE LEFT. YES… THAT'S IT… NYEH… HEH… HEH."

Papyrus heaves a sigh.

Undyne had crossed paths with the skeleton in question on her way back home, still fuming over the confrontation. She'd grinned with sharp teeth at his back, then it had faltered slightly as the short skeleton's words had played out again in her mind. Then she'd heard him speak out loud, and he'd sounded so… sad. Aww, hell. Maybe she could kill two birds with one stone. The shorter, somehow weirder one hadn't said a full day after all. "What's up nerd?"

"O-OH, UNDYNE. I… IT'S NOTHING. YOU HAVE TO GET BACK TO SEE GERSON, RIGHT? LET ME GET OUT OF YOUR WAY…" He unfolds himself from where he'd been sat on the floor and starts to head back towards the capital. This was so unlike the loud, brash skeleton that irritated her daily that she feels a small quirk of sympathy.
"Who's 'he'?"
"Who's who?" The skeleton's head swivels around as he tries to find the 'he' he thought undyne was on about.
"No… not-" she growls a little bit before taking a breath. She wasn't going to survive today without punching this nerd, was she? "You said 'he hasn't forgotten about me'. Who's that 'he'?"
"OH! THAT HE IS SANS, HE'S MY BROTHER. HE WAS SICK FOR A LONG TIME BUT HE WAS OBVIOUSLY FEELING BETTER BECAUSE HE LEFT HIS ROOM AT THE HOSPITAL. ACTUALLY, NOBODY SAW HIM LEAVE BUT HE HASNT WORKED SINCE THEN AND HE HASN'T CALLED OR SPOKEN TO ANYONE. HE MIGHT JUST BE HIDING, HE WAS THE BEST AT HIDE AND GO SEEK - EVEN BETTER THAN ME AS HARD AS THAT IS TO BELIEVE! HE THOUGHT I DIDN'T KNOW HE LET ME WIN, BUT IT WAS OBVIOUS."
"...is he about so high with a blue hoodie and a stupid grin on his face?"
"YES!" she watches him just light up. She's going to deny the fact that even helping him that simply made her feel at least a little good. "SO YOU'VE SEEN HIM?"
"Today, actually. He told me…" something in her tells her it's a bad idea to let him in on the deal "he told me to say hi after my training with Asgore. We could go see if he's still there?"
Papyrus looks at her, thoroughly perplexed. "THIS IS NOT ONE OF YOUR JAPES, IS IT?"
"Nah, but if you wanna come you'd better come. I'm not going to stay here forever."
"THEN WHAT ARE YOU WAITING FOR?!" He grins and bounds off. She sighs and starts to follow him. She debates just turning the fuck around and hoping out while his back's turned and just saying she spent the whole day, but a shudder goes through her. Is she being watched? "COME ON UNDYNE!"

She briefly looks about her, but there's nothing that she can see. The feeling doesn't shift. She starts following the tall skeleton with a sigh.

"WAIT A MOMENT." Undyne pauses as Papyrus starts to dig through his satchel that he'd still had with him from school. He pulls out a small desk fan, but the wire that would have plugged in had been cut off at about a foot long and went into a small black box. He holds it out to Undyne with a grin. "YOU HATE HOTLANDS MORE THAN I DO, SO HERE! I, THE GREAT PAPYRUS, SHALL LEND YOU THIS!"
"I… what? I mean, what the hell is this thing?" nice save.
"IT'S A FAN " He narrows his eyes at her like she just asked what two plus two was.
"I KNOW THAT, DORK! Aren't you supposed to plug them in?"
"OH! NO, THIS" he waves the box "MEANS I DONT HAVE TO, AS LONG AS I REMEMBER TO CHARGE IT. AND I, THE GREAT PAPYRUS, NEVER FORGETS SOMETHING LIKE THAT - I CHARGE IT AT THE SAME TIME I CHARGE MY PHONE TO MAKE SURE."
She shrugs, and hits the 1 button. She's met by a gentle whir of fan blades and a gentle breeze. Wow. He starts into hotlands itself, and she follows. She ups the speed of the fan, and while it doesn't do much to cool the intense heat, the air being moved certainly does help with the dryness. She feels like a dork carrying it though. "Where did you find this?"
"IN THE LAST PILE OF GIFTS THAT SANTA LEFT WITH SANS AT THE LAB. THAT'S WHERE HE LEAVES THE SPECIAL THINGS THAT HE AND HIS ELVES MAKE FROM SCRATCH, YOU SEE, SO IF THEY DON'T WORK WHEN I TRY THEM, SANS CAN FIX THEM. HE TELLS SANS HOW SO HE CAN SPEND MORE TIME DELIVERING TO EVERYONE ELSE!"

Undyne stares at him. "You… You're fucking kidding me, right? You know that-" she feels something tug her leg out from under her and her face meets floor before she knows what's happening. She growls but upon looking, the only person there was Papyrus, and he was a foot in front of her. "-what was THAT?!"
He sees her on the floor and picks her up like she was a bag of sugar, and sets her back upright gently. That makes her blink in surprise - she might be thin but she's not light being all muscle.
"PLEASE, BE MORE CAREFUL. YOU MIGHT HURT YOURSELF!"
"I… must have tripped." She knows she didn't but what's she going to blame? There's nothing there. "OH SHIT, THE FAN!" she cries, seeing it having buckled under her weight when she fell. It had stopped rotating, and she picks it up neither of them can make it start again. Papyrus simply shrugs and laughs it off as he puts it away.
"THAT JUST MEANS WE HAVE ANOTHER REASON TO FIND HIM NOW! NYEH HEH HEH HEH HEH HEH! LET US GO. WE SHALL GO TO THE NICE CREAM MAN FIRST."

She blinks harder before following.

Papyrus refuses to let her pay for the nice cream. He also carries her through the hottest part when she's starting to feel too tired to go on. She had been starting to really dry out and he'd simply picked her up and piggybacked her until they reached the fountain at capital. Sure, he'd dropped her in it, but by now she was sure that he didn't mean it meanly - and he hadn't, it was just the quickest way he could think of to get her moist again. She'd actually found it kind of hilarious.
Hell, she didn't think she had it in him whatsoever to be any kind of mean, but now she was starting to see that just because he was a weanie didn't mean he was a bad weanie. "Hey, ner- uh, Papyrus."
"YES?"
"Why are you so… nice?"
"WHAT?"
"To me, I mean. I was… I was kind of a dick to you."
"OH THAT'S SIMPLE!"
"...AND?!"
"BECAUSE YOU DIDN'T MEAN IT!" He grins at her. "EVERYBODY, I THINK, HAS THE CHANCE TO BE NICE. EVERYBODY IS A GOOD PERSON, SOME JUST HAVE TO TRY HARDER THAN OTHERS! AND YOU MUST HAVE HAD YOUR REASONS FOR BEING 'A DICK' AS YOU PUT IT, BECAUSE YOU'VE ONLY BEEN NICE TODAY AND THAT PROVES MY POINT! NOT THAT I, THE GREAT PAPYRUS, AM NEVER WRONG!" he pulls a pose, and then quickly adds the quiet addendum "ABOUT IMPORTANT THINGS ANYWAY."

Heh, it hadn't even taken a whole day. Good old Pap. Loneliness stirs within him as he watches. He can just imagine all the things his brother would be telling him he's done wrong since he left, and how to do better. He returns to his room through a shortcut satisfied he doesn't need to keep an eye any longer. He misses his brother. He needs to leave.

By the end of a day passed with laughter, she's convinced that Papyrus is just about the sweetest monster she's ever met and possibly in the underground full stop. She'd sort of known it anyway, and that's why she'd been so mean to him… monsters like that aren't going to be anything but fodder when the humans come or they break the barrier, whichever came first, and she was trying to toughen them up a bit. And now… she's thinking two things. A) His brother had been right and B) maybe she's been thinking about this all wrong. Undyne and Papyrus eventually reach the hall where she had spoken to his brother, and she hadn't expected him to be there still but she had kind of hoped he was going to be for Papyrus' sake.
"Sorry, he was here. I'm not sure where he went after this. Maybe we could ask Asgore if he's seen him?"
"NO, I'M SURE HE'S BUSY. BESIDES, SANS WILL BE FOUND WHEN HE WANTS TO BE." He laughs to himself, and it puzzles Undyne a little. Then she remembers what he was saying earlier.
"Hey, tell me a story."
"WOWIE, REALLY?!"
He lights up with the most excited and passionate expression she's ever seen. It lights a fire in her soul. She responds with just as much passion. "OF COURSE! it'll give us something to talk about on the way to Waterfall!"
"BACK TO…" his eyesockets fill with excitement, and she laughs. "YOU LIVE IN WATERFALL, RIGHT? I, OF COURSE, SHALL WALK YOU HOME! THE GREAT PAPYRUS IS A GENTLEMAN AFTER ALL!"

Man, she really feels bad for picking on this kid. She has a strong feeling that that was the point of the deal.

"YOU WANTED A STORY, YES?"
"HELL YEAH! What makes you so sure he'll turn up? There's a story there, I can tell."
"ABSOLUTELY! THE DAY BEFORE THIS HAPPENED, ME AND MY BROTHER HAD A DISAGREEMENT ABOUT… I DON'T REMEMBER WHAT, ACTUALLY, I FORGAVE HIM FOR IT LONG AGO SO IT WASN'T IMPORTANT TO REMEMBER IT. BUT THE NEXT DAY HE WAS STILL BEING GRUMPY SO I SUGGESTED WE PLAYED A GAME TO CHEER HIM UP. HIDE AND GO SEEK WAS ALWAYS HIS FAVOURITE SO THAT'S WHAT I PICKED. I STILL DON'T KNOW WHERE HE HID, BUT I LOOKED FOR, LIKE, THE WHOLE DAY. I WAS SCARED THAT HE'D GOT LOST, AND AT THAT POINT HE APPEARS AND HE TOLD ME THAT I SHOULDN'T BE SCARED BECAUSE EVEN IF I COULDN'T SEE HIM HE WOULD BE CLOSE." Papyrus very much leaves the crying out of the story because he doesn't want his cool new friend to know that bit. Undyne slaps him on the back a little too hard, but he thinks it's meant to be consoling.
"Sounds like you're right! And I know he's looking out for ya in the mean time, nerd!" She grins at him, and he nods back with his own grin.
"NYEH HEH HEH HEH, I NEVER DOUBTED IT! I JUST... REALLY MISS HIM."

She never apologizes for her behaviour, and nor does she have to. She just vows to herself to treat him better. She doesn't sees Sans again for a long while, but sometimes when she and Papyrus are hanging out, she still gets that feeling of being watched.