Well, this is nerve-wracking as hell because I've really liked writing this idea but it's unbetad and rambly as all hell so aaaargh please say this makes sense to somebody and isn't an entirely terrible idea

Contains nonverbal Frisk, because a lot of the fic I've been reading has a to-some-degree nonverbal Frisk, possessed by a very verbal Chara, and headcanons errywhere about what's up with the skelebros and Gaster

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But somewhere out there, at the point where the parallel universes tangle, are a million minds just like yours. For a very obvious reason.

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Snowdin's abuzz in the days after the barrier was broken. The whole Underground rushed to the surface to feel real sunlight on their skin (or fur, or bone, or scales, or flames), but despite everyone's reluctance to ever have to live underground again, it takes time to set up a New New Home and besides, most of you left your things behind.

You don't want to dampen your brother's enthusiasm as he zooms around the house, packing his books and bones and strings of lights and racecar bed and reminding you not to forget your pet rock. Or your socks. You're feeling more energetic than usual yourself at the sight of something new, a future that neither Frisk nor Flowey seems inclined to reset, and the hope that you'd long since thought had died is rekindled that maybe you'll never have to wake up to a day you've already lived again.

But rather than the future, it's the past that's worrying you.

You haven't bothered to pack too much-the fear of everything being reset has dwindled but not died altogether. You've shoved a couple of books and the pie recipe that Toriel gave you about a year ago (probably, in linear time, but you're not very good at keeping these things straight) in your pockets, but you aren't really very attached to much of your stuff. You don't have anything that you care about more than Papyrus, and he's definitely coming with you. You made yourself stop caring too much a long time ago (though you know how much you could care about some people, if you'd only let yourself, if you could feel safe that you wouldn't wake up in the morning loving somebody who's barely even met you), but nothing, not even the fragility of reality itself can, or will, or has, made you stop caring about your brother.

Papyrus often complains that he doesn't know what you'd do without him. You do, and you know for empirical fact that the world is better with Papyrus in it.

You just want to leave with him to the surface, to a world where nothing can be reset, everything is final, everything is permanent. To you, it sounds so secure, so exciting. But you also know, staring at the broken old machine in your shed, that if you don't figure this out now, you'll go to the surface and never come back and never, ever know what you've forgotten. All you remember is that you knew you were going to forget, and that it was then, not when Alphys accidentally created a homicidal flower with the power to reset time, that you began to question if it was worth waking up in the morning, knowing that you wouldn't even remember…

What?

"SANS!" Papyrus calls, barging into the shed as you're staring at a note with familiar handwriting that you don't recognize. "YOU MUST HURRY AND FINISH PACKING YOUR THINGS! WHAT IS THAT?"

"dunno," you say, folding it up and pocketing it quickly. Then, because you can't resist, you tug at the dustcloth covering the machine and add, "bonely one more thing to sort out."

"SANS!" Papyrus cries in automatic exasperation, but he's also grinning despite himself, so mission accomplished. "I SHALL LEAVE YOU BEHIND IF YOU CONTINUE TO BE FOOLISH!" He looks uncertainly at the machine. "HOW DO YOU INTEND TO MOBILISE THIS CONTRAPTION?!" he demands.

You wonder if it means something that he doesn't ask what it is. Does he remember? Or does he know that he's forgotten? "ain't sure," you say, deciding that you have to probe. You don't want to spoil Papyrus' mood, but you can't afford to keep dancing around this like you have ever since the two of you came to Snowdin. "was tryin' to remember how we brought it to snowdin in the first place. we musta done, right?"

"AH, YES… WHEN WE CAME TO SNOWDIN…" Papyrus says uneasily. He's quiet for a long moment, eyelights downcast, perpetual grin somehow turning down. "BROTHER… I DON'T REMEMBER WHERE WE LIVED BEFORE WE LIVED IN SNOWDIN. OR HOW WE GOT HERE, ACTUALLY." He wrings his hands. "I'VE TRIED, BUT I JUST CAN'T… I'M SORRY, BROTHER, I-!"

"hey, it's okay, bro," you say, reaching up to wrap your hand around one of your brother's jittery wrists. "i don't either."

"BUT WE MUST HAVE LIVED SOMEWHERE!" Papyrus cries. "I REMEMBER PUTTING UP THE LIGHTS FOR THE FIRST TIME, RIGHT AFTER WE MOVED IN, BUT I DO NOT RECALL WHERE WE MOVED FROM!"

"me neither," you assure him, squeezing his wrist. "i don't remember a shin-gle thing."

"SANS, BE SERIOUS!" Papyrus demands. "WHAT IF WE FORGET THE UNDERGROUND WHEN WE LEAVE?! I AM MOST EXCITED TO LIVE ON THE SURFACE, BUT…" He looks down unhappily at you. "IT HAS NOT BEEN COMPLETELY AND UTTERLY NOT-COOL ALL OF THE TIME, HAS IT? I DO NOT WITH TO FORGET OUR MEMORIES WITH UNDYNE AND GRILLBY AND THE HUMAN AND…"

As your brother lists off people he doesn't want to forget, you want to reassure him, but the possibility of what Papyrus has suggested stops you cold. Could you forget? You don't know how or why you forgot before, and you don't know any other skeleton monsters. Maybe forgetting your past when you move to a new place is normal for you. After all, you knew that you were going to forget, you remember that much. You remember your first days in this new house too, hating the feeling of your memories slipping away from you so much that you could barely stand to stay awake, long before any flowers or children with time in their hands started unravelling the world under your feet.

While you don't know any other skeleton monsters to ask, you do know somebody who knows more about magibiology than anybody else in the Underground. "tellya what, bro," you suggest, "let's go talk to alphys." True, most of her experiments have been truly horrific failures, as the Underground's lately discovered, but she did successfully build Mettaton a solid body and she might have an idea about what's up with you and Papyrus. So long as you don't let her perform any experiments on you, it should be fine.

At the last second, you decide to take a shortcut and take the broken time machine with you, just in case.

{}

You die. Every second, you die, in a different world, in a different way. When, in the course of linear time, you reach the point where you most commonly die, it feels like the migraine will split your skull in two, and for once Papyrus doesn't nag you for staying in bed.

{}

Alphys stares at her readouts from her scan of the two of you the whole time Papyrus is explaining the problem, and you really wish you knew what that growing frown of hers was coming from. Undyne's present too, and listening curiously while suplexing stacks of comic books into boxes that you can tell don't have the dimensions to contain the mass being forced into them. Against physics, however, Undyne seems to be winning.

"I've, uh, never, uh, heard of anything like that," the Royal Scientist says, wringing her claws nervously and staring fixedly at the readouts. "I've also never seen, um, I mean, wow, your magic, it's actually… I had no idea you guys were so powerful." She glances from the two of you to her readouts and backs away a nervous step. Papyrus doesn't notice, too busy preening. You shove your hands deeper into your pockets. "B-but I don't think there's, uh, a sp-spell or anything like that actually, um, on you…"

"BUT THEN WHY DO WE RECALL NOTHING BEFORE OUR ARRIVAL IN SNOWDIN?!" Papyrus cries in distress. "PERHAPS WE DID NOT EXIST AT ALL?!"

"What're you talkin' about, Pap?" Undyne asks with a scowl, taping another box into submission. "'Course you existed! I remember you punks coming through Waterfall, looking for a new place! You bitched and moaned about mildew in your joints until we got into a FIGHT!"

"...I DO NOT RECALL THIS," Papyrus says, looking confused. You don't remember either, but come to think of it you're really not sure at all when you first met Undyne, and the certainty in her words gives you an unaccustomed spark of energy.

"Suuuuure you don't, just because I kicked your bony butt while your brother was having a nap!" Undyne says with a proud grin. "But you fought so damn well I told you you might be Royal Guard material someday, remember? No way you forgot that!"

Papyrus' troubled expression tells you that he has, and it strikes you that you, too, have no idea when Papyrus' ambition to join the Royal Guard 's wanted it for as long as you can remember, but messed-up timelines aside, that's not actually all that long.

"if we were comin' through waterfall, maybe we used to live in hotland, huh?" you muse. "hey, doc, maybe that's when we first met, huh?" You shove your hands a little deeper in your pockets. "i mean… i never wanted to bring it up, but y'know, it strikes me that i dunno when you and me started textin' and talkin' physics."

Surprisingly, Alphys looks relieved. "O-oh my god, I-I-I thought it was just me," she sighs. "I, uh, I didn't want to say anything either, I just, uh… I thought I'd forgotten because I was dumb or something…"

The response from Undyne and Papyrus is instant and in perfect harmony. "YOU'RE NOT STUPID! YOU ARE THE SMARTEST MONSTER IN THE UNDERGROUND AND THE MOST AMAZING GIRLFRIEND IN THE WORLD!"

"...ACCORDING TO UNDYNE," Papyrus adds cheerfully. "SAY! IF DOCTOR ALPHYS HAS FORGOTTEN HOW SHE MET YOU, BROTHER, IT MUST NOT BE A SKELETON THING! MAYBE IT'S A HOTLAND THING!"

"Ummm… maybe?" Alphys says, running to one of the newly-cleaned desks to check one of her computers. "I-I mean, there, um, haven't been any other reports of memory loss, but, um, I don't actually remember when I started working here either…" Her speech is a little smoother when she's looking at a computer screen instead of your faces, you note; she's certainly confident enough when texting, even making her own puns and jokes. You haven't really talked to her in person all that much, really, not that you can recall, just texted about spacetime anomalies and junk food at weird hours of the night. "I remember getting about halfway through college, and then there's this, uh, this gap… and then I was working here, alone, and then, uh, K-K-King Asgore said we didn't have a royal scientist and we needed one so, um, would I like the job? And I found out I had like three doctorates that I, um, don't remember getting, but, uh, they were legit, and the University said their records said I'd gotten them while working in the lab for, um, well, it said a Doctor W.D. Gaster…"

"WHO… MIGHT THAT BE?" Papyrus asks. You clench your fists in your pocket. You don't remember a Dr Gaster, but you know the name, and it hits you with such a wave of sadness that you're certain that you've forgotten him.

"Ummm, I think he was the Royal Scientist before me, but, um, well, when I asked the King about him he, uh, I mean, King Asgore, he didn't know who Dr Gaster is. B-but, umm…" She looks around, opening a few drawers. "I kept finding his notes and things, uh, I kept them in a folder somewhere, um, I swear I do have them…"

"That big black folder full of notes in weird handwriting? I already packed it," Undyne says, looking around. "Innnnn… that box!" She leaps on the package in question.

"Oh, Undyne, you don't have to, um… never mind," Alphys mumbles as Undyne rips off the packing tape and pulls out a thin black ringbinder. "Thank you…"

"Hey, if this dude Gaster's done some weird science or something to my friends, we gotta find him and kick his ass!" Undyne declares, conjuring up a spear and casually spinning it around her head. "So what do they say, anyway? I didn't really look at 'em, and I don't think I could read that goofy handwriting anyway…"

Alphys opens the folder, leafing through a few notes. Papyrus rushes over to look, dragging you with him, causing Alphys to cringe backwards and practically throw the folder at the pair of you rather than share it. "THANK YOU, DOCTOR!" Papyrus says jovially, looking at the notes in the folder. "HMMMM… I HAVE NO IDEA WHAT THIS MEANS! SANS, WHAT'S A PHOTON READING? WHAT KIND OF BOOKS DO PHOTONS READ?"

"it's a physics thing, bro," you say, reading the page and knowing that there's no way you can explain the contents of these notes to your brother, not least because a 'negative photon reading' isn't actually a possible thing. Though the handwriting is definitely weird, you find that you can read it quite easily, and even know what the shorthand notation means. Most of the notes are describing various odd occurrences around some project, signed off as having been witnessed or verified as having occurred by Gaster or other scientists that were presumably his assistants, though you don't recognize any of them except one.

"hey, alphys, this report's signed by you," you point out. "thought you said ya didn't know this guy?"

"Ummm, I d-d-d-don't," Alphys squeaks. "B-but, uh, yeah, m-my name's on some of the, uh, notes, and the project, even though, I, uh, I don't remember…" She twiddles her claws a bit. "I'm, uh, not the only one who, I mean… Um, you should probably keep reading…"

You do so, coming across a minor flare-up of some sort that had affected but not seriously injured two members of personnel, one being Gaster and the other…

"WHY, BROTHER, THAT IS YOUR NAME!" Papyrus gasps, grabbing your shoulders. "IT SAYS YOU WERE INJURED IN AN ACCIDENT, SANS! ARE YOU ALRIGHT?" He hugs you tightly, as if you're about to suddenly collapse from terrible injuries.

"i'm fine, bro," you promise him, patting his arm, even though you're feeling very shaken. "you know me-nothin' gets under my skin."

"YOU DO NOT HAVE ANY SKIN, BROTHER!" Papyrus protests. "NEVERTHELESS, SCIENCE IS VERY DANGEROUS INDEED! YOU MUST LEARN TO BE MORE CAREFUL!"

"will do, bro," you promise. "hey, alphys, whaddya think happened to this gaster guy? where is he?"

"Well, um… I-I dunno," Alphys says, retreating back behind her computer. "I, uh, can't find anybody knows him, y'know? But, um…" She takes a deep, deep breath, and Undyne slings an arm around her, apparently steeling her courage somewhat. "We weren't getting power from the Core when I was in college," she blurts out. "All the lights were magical, or just regular candles, and all the technology was powered by magic, but when I became the Royal Scientist, the Core has just gone online..."

"Yeah, I remember when that thing got activated! It was wicked!" Undyne exclaims. "Not havin' to use magic to keep the lights on or run the fridge or anything sure made life a hell of a lot easier!"

You don't remember the Core coming into use either. It's been there as long as you can remember.

"I, uh… I think this project in the notes, I mean, the one that I was working on and, uh, you were too… I think it was the Core," Alphys hypothesizes. "I, uh, none of the other people in those notes remember Doctor Gaster either, but, uh… something must've happened, I think. I mean, it can't just be a coincidence, right?"

"i'm with you on that," you say, surprised by how badly you want to find him. "i think we've all got some questions for this gaster guy."

{}

You are at least a little aware of other times, past and future, at all times, but sometimes you can fuzz it out… and sometimes a million of you flow together, your thoughts in sync. Millions of minds, just like yours, all at once.

But no matter how much of the past and future you can feel, you still can't fill the gap. None of you can.

{}

"knock knock," you call, rapping your knuckles on the door to the Ruins. You listen for a moment to the distant sound of footsteps approaching down the hall on the other side.

"Who's there?" Toriel calls, already giggling a little in the anticipation of a terrible pun.

Well, there's no way you can disappoint her. "Iva," you say.

"Iva who?"

"Iva sore hand from knocking," you reply.

Toriel laughs. "Well, I'd better let you in and look after your poor hand, hadn't I?" she says, opening the door with a warm smile. "We've nearly finished packing, but we left the kitchen things for last and there's a pie fresh out of the oven!"

"my trapieziod feels better already," you say, making her laugh again as you follow her through her basement and up the stairs, following the smell of pie. "lookin' forward to livin' on the surface?"

"Oh, yes!" Toriel says happily. "I'm trying to bring as many of my flowers as possible, too, so they can have some real sunlight and rain. I'm sure they'll get even more beautiful!"

You can't help hesitating in the kitchen doorway at the sight of Frisk, but the child's doing nothing but sitting at the table and eating a large slice of pie with their hands. Toriel chastises them for not using their cutlery, and you feel yourself sweat at the sight of them picking up a knife and fork, but all they do is eat pie, and you force yourself to be calm. This isn't a timeline where either of you kill the other, and you're less than a day from living on the surface, in a vast, beautiful, sunlit world that keeps moving forwards.

"thanks," you say as Toriel hands you a slice of pie. You cut yourself a bite. "wow, that somehow tastes better'n it smells!"

"Oh, thank you," Toriel says with a smile, sitting down with her own slice. "Are you and Papyrus finished packing?"

"pretty much," you say. "just been helping alphys and undyne with a coupla things. hey, tori? didja know the royal scientist before alphys?"

Toriel frowns, shaking her head. "I left asgore a very, very long time ago, and I haven't been involved with affairs of the kingdom since then," she says quietly, her tone when she speaks of her ex-husband containing a bitterness that does not belong.

"ah… guy named gaster? never heard've him at all?" you ask. "it's just, uh… well, we were helpin' alphys and undyne pack, and we found out he's the guy who built the core. problem is, he didn't leave any instructions about turnin' it off, or if it's safe to leave it on. don't wanna press the wrong switch and cause a core-tastrophe, huh?"

Success: Toriel giggles, smiling again. Frisk doesn't respond; they've stopped eating and are staring blankly down at their pie. Looking closely, you see that their lips are moving soundlessly, their hands twitching. They frown, then notice your attention, smile brightly and shove half of their remaining pie into their mouth.

"Frisk!" Toriel cries. "Smaller bites!"

"can't blame the kid for wantin' the whole pie in their face at once," you tell Toriel, taking a forkful of your own slice. Maybe Asgore will remember something to tell Alphys, or Undyne and Papyrus will be able to track somebody down.

Toriel isn't in contact with many people, but she calls some of the people whose numbers she has, and nobody has ever heard of Gaster.

{}

You know what her pile of dust looks like, and you know how she smiles when she first sees sunlight. They're not quite your memories, not clear and linear; more like jagged fragments, deja vu of nothing. The moment you met the kid, you knew that you had met them, will meet them, were meeting them all at once. You are aware that they can, will, have killed your brother; they can, will, have killed you; you can, will, have killed them.

They can, will, have been your friend, and take you all to the surface. All you can do is hope that you live in one of those timelines, and wait to find out.

{}

"So the King not only doesn't remember Gaster, he didn't even realize that there were, like, twenty-five years between Doctor Spiro getting dusted by a human and Alphys getting hired," Undyne summarizes when she strolls back into the lab. "I guess when you're centuries old, a quarter-century isn't really anything? Did either of you find anything?"

"I SPOKE TO EVERYBODY IN THE UNDERGROUND, AND NOT ONE OF THEM HAS EVER HEARD OF DOCTOR GASTER!" Papyrus declares. "SANS WAS JUST ABOUT TO TELL ME ABOUT TEA WITH THE QUEEN AND THE HUMAN! THE HUMAN MET EVERYBODY DOWN HERE! PERHAPS THEY MET THE DOCTOR?"

"they didn't say anythin'," you say with a shrug. "tori asked around, but we couldn't find anybody who knew about the guy. you know she hates bein' called the queen, right? she left the king a long time ago. think she considers it her crowning achievement."

"I HOPE THEY CAN BE FRIENDS AGAIN," Papyrus says sadly. "EVERYBODY SAYS THAT THEY USED TO BE A HAPPY FAMILY WHEN THE PRINCE WAS ALIVE…"

"Ummm… y-yeah, they were," Alphys says nervously, twisting her claws in her hands. "I, ummm, maybe sh-shouldn't share this, but, uh… there are videos here, in the archives, that, um, well, th-they're videos of the R-Royal family, back before, um… I-I should p-probably give those b-b-b-back to the K-King, huh?"

"I'll take 'em back to him!" Undyne volunteers. "Did you find anything about our missing Doc?"

"W-Well… there were, ummm, some plans for, um, what l-looks like the machine you brough, S-Sans," Alphys says, gesturing to the broken device that you've never managed to repair because you can't even figure out what's wrong it, or what's right with it. "I, ummm… I think it's, uh, it's supposed to be connected to the Core, or, uh, use a component from the Core, maybe. Uhhh, you could, um, try having a l-look at the main console...?" She shakily holds out a key. "Th-this elevator key ought t-to, uh…"

Your palms are sweating, somehow, when you take the key. You don't remember the main console of the Core, but you're afraid of it.

"TO THE CORE, BROTHER!" Papyrus declares, scooping you up and charging off towards the elevator.

{}

There must be other yous going to the Core now. The closer you get, the louder you can hear their thoughts, like echoes when they're the same and clanging cacophonously when they aren't.

You aren't quite sure which thoughts are this you. You only know which thoughts aren't when they end.

{}

The light of the Core pulses erratically, every colour all at once, so bright you can barely make out the control console at the end of the walkway in front of you.

"THERE ARE NO HANDRAILS ON THIS WALKWAY!" Papyrus says indignantly. "WE ARE VERY CLOSE TO THE LAVA! THIS IS MOST UNSAFE! SOMEBODY COULD GET HURT!"

"yeah," you mumble, rubbing your head, which feels fuller and emptier than ever all at once. You think you can hear a voice whispering in your ear, and for once, you think it isn't yours. "c'mon, let's check out that console."

Papyrus insists on holding your hand on the way to the console, even though it isn't a long walk. You don't mind, really; you're sure that Papyrus must once have been small enough to have to hold your hand as he followed you around, but you can't remember it. His grip grounds you, nevertheless, in this you, this now, which is getting fuzzier and fuzzier the closer you get to the Core's light.

You reach the console without any lava-related incidents, but you don't get a chance to have a proper look at it before you hear the elevator behind you slide open, and turn to see Frisk approaching you, staring curiously up at the reactor.

"HUMAN! WHAT ARE YOU DOING DOWN HERE?" Papyrus asks, spreading his arms wide as if to protect Frisk from even the glow of the reactor. "THIS PLACE IS VERY UNSAFE!"

I know, Frisk signs, but Doctor Alphys said you were looking down here for something. Is it Doctor G-a-s-t-e-r? Did you find him?

"nah," you say, watching the kid closely. They're chewing on their lip a little as they sign. "he mighta had somethin' to do with this thing, but we ain't sure. you need us for somethin', kid?"

Frisk raises their hands to sign again, then their face blanks for a moment. They slowly fold their hands behind their back, their nervous expression changing to something horrifically familiar, their lips splitting in a broad, malicious grin as they pull out a knife.

"I don't need any of you," the child says, taking a step forwards, "but this is the perfect place to test out something that's been bugging me…"

It's something out of your nightmares, your worst-half memories, and it's coming right towards you and your brother with knife in hand.

"Heheheheh…" Frisk chuckles, raising their knife. "Really, sans. I would've thought you of all people would remember what I'm capable of…"

"HUMAN! YOU ARE TALKING!" Papyrus cried in surprise. "I HAVE NEVER HEARD YOU SPEAK SO MUCH AT ONE TIME! WHAT ARE YOU DOING WITH THAT KNIFE? IS THAT UNDYNE'S?"

You barely have time to process what's happening before you have to lunge to push Papyrus aside as Frisk charges you with the knife. It scraps just past your elbow. You feel the edge of knife graze bone.

"HUMAN! THAT IS DANGEROUS!" Papyrus exclaims. You conjure up a barrage of bones that ripple across the ground towards Frisk, forcing them to back away to avoid them, stumbling perilously close to the edge of the walkway. "SANS! WHAT ARE YOU DOING?! YOU COULD HURT THE HUMAN!"

"hate to break it to ya, bro, but frisk is tryin' ta hurt us!" you yell, turning Frisk's SOUL blue to pin them to the floor, both keeping them from attacking easily and keeping them from falling off the walkway. Part of you knows you've killed Frisk many times, and that Frisk has killed both you and Papyrus many times and is fully capable of doing it again, but it's still difficult to face that their turnaround wasn't genuine this time. All that time they spent not fighting Papyrus, eating his spaghetti, talking with him on the phone, eating burgers with you at Grillby's… how hard they fought to SAVE you all…

It's hard to believe that it was all a bluff, but that's a real knife in Frisks' hand and they're grinning a horrible grin that you haven't seen on their face in this time as they attack you with it. One hit could kill you both, and you're not going to let that happen to your brother.

"HUMAN! PLEASE PUT THE KNIFE DOWN!" Papyrus calls out. "PLEASE TELL US WHAT HAS HAPPENED! WE ARE YOUR FRIENDS! LET US HELP YOU!"

Frisk doesn't respond, just grinning, and you'd dearly love to just take them out before they get too close to your brother, but you know how much faith Papyrus has in Frisk and you don't want to know how he'd respond to you killing the kid in front of him. He's never alive in any timeline where you killed Frisk, after all, and in every one of those, he believes in them until his death.

You don't know what you'd do if Papyrus hated you, but you will not let him die again. You summon up a gasterblaster to fire on Frisk-

You stare up at the monstrous floating head for a moment as it charges up its shot. gasterblaster. You've never called on in this timeline, never gotten into a serious enough fight alone, and you've never really thought about why all of you call them that…

You hesitate to contemplate a moment too long, brain fuzzing with the deaths of you surrounding this moment in time. "HUMAN! STOP!" Papyrus cries in horror as the knife stabs towards your sternum-

"What the hell?!" Frisk yelps as they stop in mid-stab, tugging at their arm. Something's grabbed at their wrist, keeping them from moving. It's a white, skeletal hand, not unlike yours or Papyrus', but with a large hole in the middle of the palm.

The light of the Core is pulsing erratically. The hand jerks, tugging Frisk into nothingness, the Core flashes black, and everything goes dark.

"SANS?" Papyrus asks tremulously. "DID YOU DO THAT?"

"not me, bro," you say shakily. Your gasterblaster is gone and you can't summon it back, but you let your power glow out your left eye, creating a blue searchbeam that swoops across the room as you look around. The Core is still on, but its glow is black instead of light. "whatever that is, it probably ain't good. c'mon, let's get outta here."

"BUT WHAT ABOUT THE HUMAN?" Papyrus asks as you grab his hand and lead him towards the door. "WHERE HAVE THEY GONE?"

"frisk can handle themselves, you know that," you assure him. "c'mon, let's get-"

Behind you, the Core sends out a massive blast of energy into you and Papyrus, slamming you both into the elevator doors before you can react.

{}

A conversation you don't hear:

"ATK: 66. DEF: 66. Gaster watches, adrift from space and time… creep. Watch out for that blaster!"

Let me ACT! Doctor! We're not here to fight you! Please listen to me!

"Can he even understand you? Blasters!"

I see the blasters! Stop bugging me! I've gotta figure out a way to get through to him… he's kinda the same as the Lost Souls, right?

"Hugging it out's probably not gonna work this time. Does he even have a body to hug? Blasters!"

There are other ways to get through, though. Stuff he cares about. We'll find a way…

"Do we have to? Why're we even here? We don't even know this guy!"

We decided that we were gonna get all the monsters out to make it right, didn't we?

"You decided! We don't owe this guy anything! We never killed him! We haven't killed anybody in ages!"

You don't get points for not killing people.

"Why not? We could. We have. And then we stopped! Saving anybody is really more than we gotta do to not be terrible, right? Blasters!"

I know! About the blasters! And we're going to SAVE him!

"Fine, whatever, it's your body stuck out here in the infinite nothing while I'm just the the chump stuck along for the ride on your intergalactic guilt trip… How are you planning to SAVE him, anyway?"

Well, if what you said was true…

"Have I ever lied to you? Does this guy have anything except blasters?"

Yes and I dunno. Doctor! What's a skeleton's favourite instrument? A trom-Bone!

"His face doesn't move, but he seems to have been listening. Really? That's all you've got? What're you gonna do now, tell him your favourite spaghetti recipe? "

Doctor! Hey, I've got a great idea! Boil noodles for twelve minutes-

"...You told him your favourite spaghetti recipe. Good thing there's no time here…"

{}

Pain is flashing across your skull and spine. Emptiness is echoing in your mind.

"papyrus," you croak, fighting not to yell in pain as you pop your left shoulder back into its socket, wincing against the brightness of the light now coming from the Core. "bro, you okay?"

"THAT HURT," Papyrus groans. You hear his spine pop as he stands up. "OH! IT'S-" He stops dead, and you're about to make a pun to that effect before you look up and your words die in your throat.

There are hands in the air in front of you; tiny, pale human hands, reaching out. And forming around them are other hands, white and skeletal, popping into existence a bone at a time, with holes in the palms just big enough for the tiny hands of the human to fit in. Papyrus reaches out to take one of the hands, and you don't think to reprimand him before you do too, each of you taking a double hand and pulling

Pain sears through your skull, blinding you momentarily, but you don't let go of the hands, even as something collapses onto your legs. You blink away the lights in your sockets and stare at the weight on your shinbones. It's Frisk, knife missing, unconscious but breathing steadily. Next to them, between you and Papyrus, is a shifting pillar of black, silhouetted against the now-white light of the Core, and you look up at the tall figure whose hand you're still holding.

Tall, but hunched over, their body hidden under a shapeless (possibly shape-shifting?) black robe, their face is a skull like yours and Papyrus' but horribly warped; one eye socket near-collapsed, the other distorted and misshapen, their jaw is cracked and fused into a stationary toothless gape and their nasal cavities are disturbingly missing, leaving an unsettling gap of smooth bone in the middle of their face. Random cracks split their skull. Even though the face is unrecognizable, you know it, you know you do. You know the hands holding yours and Papyrus', remember them handing you a tiny swaddling of baby bones-

-"Hold your brother carefully, he doesn't have a lot of magic yet. Don't want to rattle his bones, do you?"-

-you know the ratty white turtleneck that's poking from the top of the robe-

-clinging to the collar of the turtleneck as you sit on bony shoulders, warm white hands wrapped around your shins to hold you steady-

-and he speaks, croaking wordlessly from their deformed jaw and you don't understand a word of it, but you remember that voice explaining entropy to you for the first time and it hurts when you realize how much you've lost.

"...D-?" Papyrus mumbles in shock. Gaster gently takes his hands back, leaning over to inspect Frisk. His hands don't seem entirely connected to anything under the robe as they reach to brush the human's hair out of their face. "HUMAN!" Papyrus cries, leaping forwards to scoop Frisk up in his arms. "WHAT HAS HAPPENED?"

Gaster straightens up and begins signing, translating the wordless croaks that he can't form into words. You learned to sign a few years ago-Papyrus has gone through phases of refusing to communicate in anything but "secret human codes" that he's learned from books and you humour him every time, you've spent the weeks and months it takes him to get bored talking only in strange human codes like morse and flags and French and signs, and it's come in handy again of some timelines where Frisk mostly signs instead of speaking-and you watch his hands closely, skull still spinning both from memories leaking back into copiously empty places and the sudden radio silence of the rest of you.

This human is very tired. We fought for a very long time outside of the world. They brought us both back here through sheer Determination.

"heh… yeah," you say shakily, staring at Frisk. "they're a determined kid." You look up at the steady light of the Core as you stand up, bracing yourself on the wall. "uh… do ya think we need to get outta here?" you suggest, looking to-to Gaster, your thoughts and memories are a kind of mess that you aren't used to and you need to straighten things out before you can think of him as anything else.

I think the Core will be fine, but I would like to leave, Gaster signs, shaking his head. I am… he hesitates, then signs so slightly you barely catch it. Afraid. I do not want to disappear again.

"THEN LET US RETURN TO DOCTOR ALPHYS!" Papyrus declares, straightening up, still holding Frisk. You keep your eye closely on the unconscious child as Gaster follows the pair of you out into the elevator towards Alphys' lab.

"UM…" Papyrus says as you ride the elevator, not keeping a proper eye on Frisk but instead looking to Gaster, who is visibly lurching as he moves, or perhaps limping. "THIS MIGHT BE A VERY ODD QUESTION, BUT… WOULD YOU HAPPEN TO BE…?"

You risk glancing away from Frisk to watch Gaster sign. You do not remember me. I know. I have been outside of time. I have seen both of you in every timeline, and I know that I have been taken from your memories in all of them. It is okay. It is not your fault.

"BUT WE FORGOT YOU! COMPLETELY!" Papyrus cries in distress. "LIKE YOU WERE NEVER HERE!"

In a sense, I was not, Gaster signed. But I am grateful that you did not vanish also. I was afraid that that would be the result of my being erased.

"how'd it happen?" you ask, leaning against the elevator doors so Frisk's still in your line of sight as you watch Gaster sign. "both windin' up there and gettin' back? not sure if we should remember, but, uh…" You rap your knuckles against your skull. "things're still a little messed up in here."

Gaster nods. You might come to remember that using the Core to power the Underground was a secondary concern. Magic had been working for us just fine for centuries. But Mt Ebott is a volcano, and it was building up to erupt. If the excess heat and volcanic energy could not somehow be siphoned off, and it erupted with all of us trapped down here…

You remember that you wanted to get away from Hotland and its lava, so much that you'd carried Papyrus on your back when he fell asleep rather than stop even though he was a little taller than you by then, and now you can guess at at least part of why.

I miscalculated how much time we had. The Core had to be turned on before it could be properly safety-tested. I went alone to activate it. I see that it stabilized eventually, but the first surge of volcanic energy meeting magic…

You wince, unsure if you are imagining the results or remembering. Are you implanting the black light that you saw flashing from the Core less than half an hour ago into your imagination, or have you truly seen it before, sucking in a black-and-white figure with it?

Just as you are exiting the elevator Frisk stirs, mumbling. "SANS!" Papyrus cries as the child glows blue and shoots out of his arms, skidding across the ground to sit a good ten feet away from the three of you. "BE CAREFUL! YOU COULD HURT THE HUMAN!"

"frisk's tougher'n that, bro," you tell him flatly, standing between him and Frisk as they begin to wake up, "and i ain't takin' any chances that they'll try to hurt us again." Gaster taps your shoulder, and you feel a little bad that you don't turn to look at what he's trying to sign to you, but you are not taking your eyes off of Frisk.

The small human sits up and rubs the back of their head, frowning. They look up at you and Papyrus, flinching a little at the glow in your eye, but then they look at Gaster and smile brilliantly, signing excitedly.

It worked! You're back! I knew I could get you back!

You don't know if Gaster's started signing back, but if he has, he's cut off almost immediately by Frisk speaking aloud. "See? I told you! Sometimes, trying to stab somebody works!"

Frisk signs quickly. Not every time! We're not going to try to solve problems by stabbing people every time! You weren't supposed to actually try to stab sans and Papyrus this time!

Almost simultaneously, Frisk is speaking. It's a little confusing trying to keep up with what they're saying aloud and what they're signing, because it's so different. "C'mon, you know I wasn't really trying to kill them this time," they scoff. "I mean, if I was, sasn would've died as soon as I scraped his elbow, right?" You grip your arm where there is indeed a cut in your jacket, where you thought you'd imagined the scrape of metal on bone. It's true that that would have been enough to cut you in half with any amount of real killing intent, but…

sans, I'm really really really sorry, Frisk signs to you. I'm sorry I scared you, I wasn't trying to hurt you or Papyrus- "this time"-really I wasn't! We just came to look at the Core to see if we could figure out what had happened to Gaster, then… they make a sign you don't recognize. It's the sign for "knife", but pointing towards their own heart instead of towards you.

"C'mon, it worked, didn't it?" Frisk complains aloud. "We couldn't find any of those rooms we found before"-they only show up in some timelines, you know that-"and somebody didn't want to reset again until we found one"-not unless we really had to! I thought if we looked at the Core and figured out how he fell outside of time-"are you a magiphysicist? 'cause I'm not. And, actually, I know that you're not, living in your head and all-"

They start yelling and signing faster and faster, too fast to keep up with either let alone both, and it starts to sink in that things inside of this kid's head might be a lot more complicated than you ever thought. You've spent so long trying to figure out how the kid's time control works (and how to make it stop, and what it's doing to you) that you never quite spared any to wonder why sometimes they speak and why sometimes they sign, that maybe their shift from killing to everybody to befriending everybody might be more complicated (or simpler?) than pure regret or a change of heart.

You don't get to follow that line of thought too far before Gaster collapses.

{}

…

{}

"Uh, ummm, wh-what's the-oh. Oh," Alphys mumbles, putting her head in her claws as you and Frisk come running in with Papyrus, who has Gaster draped over his back like a blanket, shifting and almost appearing to drip like liquid. "P-put him on the-on the table there. Um, is that… is… that..." She puts her head in her claws, starting to breathe fast as her eyes glaze over. You know how she must be feeling; the torrent of recollection has slowed to a trickle, but you're still spinning a little from the flood of unlocked memories. "...is that Doctor Gaster?" the Royal Scientist finally whispers.

"think so," you say, still keeping an eye on Frisk. The kid's lips are moving silently and their hands twitching as they continue to bicker with whatever else is living under their skin. "dunno what's up with him, he just-"

Gaster's hands float up, now definitely not attached to anything. I have not had a physical existence in a very long time. I lost my focus, that is all. Allow me time to concentrate and… he chuckles weakly. ...pull myself together.

"THIS IS WHERE YOU GET IT FROM, ISN'T IT?" Papyrus says accusingly, looking at you. "I THINK I WANTED TO FORGET THAT."

"what can i say, bro?" you tease him. "it's in my bones."

"Alright, boneheads, what's going on?!" Undyne demands, hands on her hips as she glares at Gaster. "Who the hell is this and what's up with him?"

"He's, um… it's coming back to me now…" Alphys puts in, going over to one of her computers. "Doctor… Doctor W.D. Gaster. I remember. He was the Royal Scientist before me. I used to work for him and I forgot…"

"I… feel like I've heard of the guy, actually," Undyne says, rubbing her forehead. "Sans, what's up with your eyes? Why're both of 'em glowing?"

"both of them?" you ask, holding up a hand in front of your left eye and seeing a shimmering reflected gleam of yellow and blue on the white bone, then moving it over your right eye and seeing the same. "what the…?"

"SANS' EYES ONLY DO THAT WHEN HE'S USING HIS MAGIC, WHICH HE DOESN'T NORMALLY BECAUSE HE'S A LAYABOUT SLACKER!" Papyrus explains.

You ignore the jibe. It's just your left eye, isn't it? Has been in every fight that mattered, which were usually against the kid standing next to you and staring at their hands, or… something else, smaller and so much bigger and more dangerous at once… the memories are hard to access now, the memories of the others of you. You can remember remembering them, feeling them, but you can't reach the memories themselves. They're gone, and so, you realize, are every other you. Your mind is so quiet because only your thoughts inhabit it now, only this you.

You hear a rapid clack-clack and look up to see that Gaster, who now appears to be sitting up, is signing your name out, letter by letter, calling for your attention.

Do you remember? he asks when he sees you looking. You were there, when I activated the Core. Thankfully, you were not sucked in too, or at least-you were not sucked in wholly. A little piece of your mind, your SOUL, was trapped outside of time with me…

"that's why i could hear 'em," you mumble. "the other timelines…?"

Gaster nods. The human used that to bring us both back to this timeline, he explains.

"HUMAN! YOU ARE A HERO ONCE MORE!" Papyrus declares happily. "WE MUST CELEBRATE, UP ON THE SURFACE!"

"Hell yeah!" Undyne agrees, fist-pumping so hard she might actually shatter the air. "...Alph, you're gonna have to explain to me what the heck is going on here later."

"Ummm… s-soon as I figure it out myself," Alphys promises.

I'm not a hero, Frisk signs slowly. I just wanted to make things right. Save everybody. They look up at you, then duck their head. Sorry.

"you don't hafta apologize, kid," you say, and while you're fairly sure that isn't true, without those other memories and other times bouncing around the inside of your skull, it's easier to see the child in front of you for what they are here and now-a child, a tiny human that giggles at your jokes and happily eats Toriel's pies (whether they're sweet or snail) and cooks fearlessly with Papyrus and Undyne and held Alphy's claw when she brought the Amalgamates back up to their families. A child who risked getting trapped outside of time to bring your-your dad back to you, just to say sorry. "we oughta be thankin' you, really. have we done that yet?"

"THANK YOU, HUMAN!" Papyrus says happily, cuddling Frisk close. "I DO NOT FULLY UNDERSTAND WHAT IS GOING ON, BUT THAT DOESN'T MATTER!"

You reach out a hand to ruffle the kid's hair. They look surprised, then smile. You know that your eyes have stopped glowing.

"You were right, y'know," they suddenly mumble, startling you. "W… I was lonely. Always alone. That was why, over and over…"

"are you lonely now, kiddo?" you ask softly. They shake their head, cuddling Papyrus' arm tightly.

"OF COURSE THE HUMAN IS NOT LONELY, SANS!" Papyrus declares loudly. "THEY HAVE US, THEIR VERY COOL BEST FRIENDS!"

You jump a little when Gaster appears next to you, standing again and moving quite soundlessly. He signs thank you to you, and to-he imitates the odd sign that Frisk did before, like a knife sign towards his heart. You figure it's probably a sign name, and resolve to ask Frisk about it later, but-not now. Now is for your family.

In any case, Papyrus drags Frisk off to mediate an argument between himself and Undyne about who is Frisk's best best friend.

Gaster turns to you and signs, I see you brought the time machine. Did you ever get it to work?

"the…?" you turn to the time machine, the device that you shortcutted all the way from Snowdin, and you remember now. Power wasn't the problem, it was-

"T-t-t-time machine?!" Alphys squeaks.

"Holy sh-sugar!" Undyne yells, staring at the machine. "You had a time machine all this time?" She squints suspiciously at the machine. "Y'know, we saw an anime where they had a time machine that was just a cheap-butt microwave, and screwing with time ended up really screwing things up…"

That is a risk, yes, Gaster signs. You can't help noticing the way the bones of his fingers bounce apart momentarily as he signs, but in general he seems to be holding himself together. We had not yet decided whether or not it was worth the risk before my accident… we ran into issues with construction. An anomaly was interfering with time, causing timelines to jump back and forth and then just… vanish…

You glance at Frisk out of the corner of your eye. "i don't think it's gonna be a problem now," you offer. "but since we're all headin' back to the surface anyways… dunno if it's worth the risk, do you?"

Certainly not for you or I, Gaster says ruefully, pausing for a moment to pointedly hold up a hand that is only occasionally attached to whatever's going on under his robe. I do not relish the idea of scattering myself across time again, in any case. He gazes pensively at the machine for a long moment. I am, of course, still outside of time, he signs thoughtfully. The me of all the timelines where I have not been returned. The parts of a million of your mind are still calling to each other, outside of time. But here, in this time, in this place… you are whole. I am whole. We are whole.

You look at your brother, who is enthusiastically planning a celebratory dinner with Frisk and Undyne, and you can remember when he came up to your elbow and told you with just as much enthusiasm about the imaginary feast he was creating with a toy kitchen set. The memories inside your head are yours, and yours alone, and they fill up all the places in your heart and soul left empty by your other selves and their pain.

"yeah, you're lookin' pretty whole," you say, pointing at his hands.

Your father laughs croakily. I am so proud of you, he signs once he has himself under control.

{}

{}

This is one of the most rambling things I've ever written oh my god

I apologize if I've screwed up the depiction or use of sign language here; I don't know it myself aside from scatty random signs I remember from a play I wrote more than a decade ago for a school drama thing that was in a collaboration with a nearby dedicated deaf school, and for some reason one of the signs that I remember is "knife". I also remember "fire", which I am 95% sure is a part of Undyne's sign name.

So, headcanons that went into this:

-sans doesn't remember other timelines fully. But when he was present at Doctor Gaster's accident, a part of his mind was also sucked outside of time and space. The whole thing's along the lines of Granny Weatherwax's situation in Lords and Ladies (SPOILERS AHOY, PLEASE PLEASE PLEASE READ THIS BOOK IF YOU HAVEN'T AND ALSO ALL OTHER DISCWORLD BOOKS, YOUR LIFE WILL BE IMPROVED) where, because all the realities are too close together during circle time and she's very finely attuned to the world of the mind, she can hear the thoughts and memories of all her other selves and gets confused about what has and hadn't happened to her and what's going to happen to her. Only sans isn't just hearing other sans' through a thin reality, part of his mind is completely outside of time and space, so he's hearing all sans' pasts, presents and futures all at once.

-Gaster is the Skelebros' dad and sole parent. He made them WITH SCIENCE. Baby monsters are usually conceived as a result of the magic generated by two monsters who love each other very much and want a child, and Gaster, being hella aro/ace but wanting to be a father, decided to see what he could do WITH SCIENCE. sans felt insecure for a while when he was a kid, worried that he'd been created solely FOR SCIENCE, but when he saw Papyrus' creation he realized that the procedure wasn't possible without genuine parental love. (Papyrus was partially created because Gaster liked being a parent and wanted another child, partially to show sans how he was created, and partially because sans wanted a baby brother.

-The skelebros grew up in the lab, which made life difficult for Gasters' assistants because whenever he interrupted an experiment to play a game or film the kids' first steps or whatever he always used the excuse "they're miracles of science and therefore definitely worth the time of everyone in this lab now give them the computer to play games on"

-sans and Gaster are the only people who truly understand gravity. Papyrus kind of does too, having picked up a lot from growing up in the lab, but he's always been more creatively inclined than scientifically so he never paid that much attention.

-Monsters generally age around the same rate as humans, with some variances depending on species; Boss Monsters living centuries seems to be unusual, and Gerson remembering the war also seems to be rare, so he's probably only lived that long because he's a tortoise monster.

-The skelebros are about nine years apart in age; Papyrus was nine and sans eighteen when the Core was first switched on, fully sucking Gaster and part of sans' mind into a void outside of spacetime. With their memories of Gaster and their own lives fading fast, the bros moved to Snowdin. This was also the time that Alphys became Royal Scientist, and Undyne was rapidly climbing the ranks of the Royal Guard. It's been nine years since then. I have no idea why all the nines. Three is an important number in storytelling, and threes and three-threes are clearly stuck in my subconscious.

-The time machine's original intent was to go back and avert the war between humans and monsters, or possibly avert the deaths of Prince Asriel and the First Child. It didn't work because of Flowey and then Frisk screwing with time. It still isn't safe for Gaster or sans to use.

-The hackable rooms appear in random timelines, which is where Frisk and Chara have encountered Gaster before; the other "figments" are other individuals who've fallen outside of spacetime, but they're from other worlds and timelines not connected to the Underground in any timeline that Frisk's been in so they're outside of Frisk's reach.

-Gaster's been able to see every time that Frisk and Chara have killed sans and Papyrus in other timelines (this is presuming that Frisk and Chara have been through every possible iteration of the timeline, from worst to best) and has tried to interfere, but hasn't been able to reach through to reality in that part of Snowdin or the Judgement Hall. Reality being a little buggered around the Core, he managed it at last.