Sans writhed against the cold tile floor of his lab, bony fingers clawing at the glowing blue barrier encasing his abdomen, tortured screams ripping from his throat. He'd never been in so much pain in his life. It felt like something was trying to split his ribcage open from the inside, the magic coursing through his bones burning like acid. He tried to hang on, tried to keep the barrier in place, tried to keep his body from violently rejecting the crystalized soul he'd forced it to carry, but he wasn't sure how much more of this he could take. Tears streamed down his cheeks as he gritted his teeth so hard he was surprised none of them cracked. He couldn't fail at this! He had to make this work somehow, even if it tore him apart! This was the only way he could bring Gaster back!

Finally, he couldn't take it anymore. Just as his vision began to fade on him, he released the barrier around his abdomen and wrenched out the crystal heart within. He collapsed in a heap against the floor, panting as the waves of pain slowly began to die down. He opened his bleary eyes to stare at the crystalized soul lying next to him on the ground. It didn't seem to have taken any damage from the whole ordeal – unlike himself – but it retained a flaming blue aura. Magic, likely what it had pilfered from Sans's own body during his short-lived attempt at carrying it. Beyond that, he'd made no progress whatsoever.

He slammed a fist against the ground in frustration. Why couldn't he do it? What was he doing wrong? The idea was theoretically sound, so why didn't it work? Was there something wrong with him? Or did his father simply not want to be brought back?

After a good long moment of self-loathing, Sans managed to lift himself up to his hands and knees, though they felt as though they were ready to give out underneath him at any moment. He reached a trembling hand out to gently scoop up his father's soul, rising unsteadily up to his feet. He had to brace himself against the wall with his free hand as he moved, taking a few stumbling steps forward towards one of his work tables. He dragged a cylindrical glass canister over to himself, gingerly placing the crystal heart within. The crystal floated in the center of the canister, still surrounded by a wispy cloud of the magical energy it had tried to absorb. Sans barely had enough energy in him to seal the container before collapsing once more. Before he could hit the floor, he was suddenly in his bedroom, slumping down against the side of his bare mattress. Consciousness left him barely a second later.

Sans couldn't tell how long he was unconscious for – it could have been days, for all he knew – but he felt like death when he finally awoke. He waited for a long time before even attempted to sit up, hoping his body would stop screaming 'the fuck did you do?!' at him. That didn't quite happen, but it did at least die down to a dull roar. He sat up slowly, his body feeling as though it suddenly weighed a thousand pounds, and he felt a light blanket slip down off of him. A small smile tugged at the corner of his mouth. So, Papyrus had been in there to check on him. He should have expected as much.

After finally managing to get up to his feet, he slowly made his way downstairs. He was still far too exhausted to use his 'shortcuts.' Luckily for him, his destination was just around the back of the house. As he made his way towards the door, he couldn't help but notice a distinct lack of Papyruses around. It didn't concern him too much. It was probably late in the day, and that meant that his brother would be off either patrolling for humans or getting his daily 'private training' with Undyne. What he was truly surprised about was the lack of a sticky note anywhere telling him that he was a lazybones and that he shouldn't sleep so much.

He was already starting to feel a bit better once he stepped outside into the snow. The cold air helped to deaden the lingering ache in his bones. Of course, that wouldn't last for long. He had to try again. He was dreading it more than he had the first time, but he knew he had to give it another shot. This was one time he couldn't afford to be lazy. After all, there was no one else he could pass this responsibility off to. He was the only one that could do it.

He slowly made his way around the back of the house, making sure no one was paying attention to him. Fortunately, no one tended to look back there. The entrance to the basement was pretty well ignored, hidden from the rest of the village by a row of overgrown bushes. Sure, one of Alphys's security cameras could technically see the door, but he'd arranged that on purpose. The camera was pointed at the back of the tool shed, and it only 'incidentally' had the basement door in view in the background. Alphys had no reason to watch that camera, anyway. Nothing interesting ever happened back there.

Sans casually made his way back there, taking his hand out of his pocket to grasp at the doorknob… only to grasp thin air. His eyes widened, his gaze finally focusing on what was in front of him. He was in the right place, but the doorknob wasn't. The door to the basement was wide open, a thin powdering of snow dusting the floor tiles just inside the threshold. A wave of icy panic washed over him. That was impossible! It had been ages since he'd even used the door to get inside his lab! It should have been locked, and most assuredly not left wide open like this!

His panic seemed to have returned some of his lost vigor, and he dashed into the lab. At first glance, everything seemed to be in order. His father's old blueprints were untouched, the machine in the back of the room still covered with that old sheet, a thick layer of dust laying undisturbed over the surface. Then he finally spotted it. It was the glass canister he'd placed Gaster's soul into. The crystalline heart was nowhere to be found, the canister lying in broken shards across his worktable.

Sans could do nothing for the longest time but stare in complete horror, his hands shaking at his sides. Of all the things that could have been broken, of all the things that could have been taken, why did they have to take that?!

After a good long freak out session, Sans eventually managed to get a hold of himself and allow a rational thought flow into his mind; he had to find Gaster's soul. Unfortunately, whoever his mystery thief was hadn't left any clues as to their identity at the scene of the crime. Fortunately, there was somewhere he could go to gleam a little bit more information on the case. He was suddenly very grateful for having arranged that security camera the way he did.

Sans was already halfway to the royal lab when he heard a stream of muffled music emanating from the pocket of his shorts. He recognized it immediately as Papyrus's ringtone. He pulled his phone from his pocket and answered the call, never once stopping as he walked along the path leading towards Hotland.

"SANS, ARE YOU UP YET?" came the somewhat impatient voice through the phone's speaker before the skeleton had even had a chance to say 'hello.'

"yeah, but i'm kinda busy right now. what's up?"

"WHEN ARE YOU PLANNING TO BE HOME TONIGHT?"

"i dunno. in a couple of hours, maybe." Sans replied, his brows furrowing. Something didn't seem right… "hey, is everything okay?"

There was an uncharacteristic silence on the other end of the line. Finally, after what felt like ages, Papyrus replied.

"J-JUST GET HOME AS SOON AS YOU ARE ABLE."

Sans opened his mouth to ask what was wrong for the second time, but his brother had hung up before he could get the words out. He stared at the phone for a long time after that. Papyrus was acting strangely. He didn't like that. He replaced his phone in his pocket and continued along the path at a jog. He had to make this quick so he could get home and see what the hell was bugging his brother. Man, why did everything have to happen all at once around here?

Sans was a little out of breath when he finally got to the royal lab. Getting around the Underground sure was a drag when you couldn't use shortcuts. Oh well. He'd be able to use them again after he got something to eat and recovered a bit of his magic, but that could wait for later. He had bigger things to worry about right now. He gave the door a good hard knock. There was the distant sound of shuffling and of things being knocked over before the door opened up a crack, Alphys's bespectacled face peeking out nervously.

"O-oh, hi Sans. What brings you out here?"

"hey, sorry if i'm interrupting anything. i think someone's been tryin' ta break into my garage. can i take a peek at your security camera footage?" he asked, slipping quite easily into his cover story for being here.

"Oh, s-sure thing!" she replied, sliding the door open for him to enter. As he did so, he couldn't help but notice Alphys's disheveled appearance; she was still in her pajamas, her lab coat thrown hastily overtop. Sans didn't really mind. He'd seen her like that plenty of times before, which was probably the only reason she'd let him in without hesitation. She led him over to the large monitor that displayed live footage from several of the cameras scattered throughout the Underground.

"W-well, here ya go! Y-you know how to use it, s-so I'll just leave you to it!" Alphys stammered out before dashing away to her computer nearby. As soon as she sat down, Sans could hear very distinct Japanese dialogue coming from that direction. Good. She would be too distracted by her anime to pay attention to what he was doing.

The skeleton didn't waste any time in queuing up the appropriate footage. An image of the back of Papyrus's tool shed filled the screen, though the door to his basement was clearly visible in the background. He fast-forwarded through the last several days of recordings, watching for the moment the door opened. It happened in a flash, but he couldn't see the exact moment it had been opened. He went back, played back the moment at normal speed. Even then, it happened in a flash. One moment the door was closed, the next moment it was wide open. Sans grumbled to himself. Okay, so this thief wanted to be a wise guy, eh? Trying to go faster than he could see, eh? Fine. He'd just pause the tape at the exact moment the door opened and—

"gaahh!" Sans exclaimed, stumbling back a few steps before landing right on his ass. He cast a quick glance over towards Alphys to make sure he hadn't caught her attention with his little outburst. Luckily, she was still too engrossed in her cartoons to take notice. Still, a blue flush of embarrassment spread itself across his cheeks. For a guy his age to get spooked by such a stupid…

He got up, dusted himself off, and looked up at the screen once more. The face that had suddenly filled the screen was that of a young monster child, its skin a sickly gray, its eyes an empty, solid white. Sans would have thought it was one of those prank videos if he hadn't recognized the face. He'd seen this kid before. He was one of those strange gray monsters that had appeared to him in his search for his father's soul, the ones who somehow knew about W.D. Gaster when no one else could remember him. But what the hell did this mean? Were the 'Gaster Followers' responsible for stealing back his father's soul? Had they just been leading him to the pieces so he'd put it back together for them? His hands clenched into fists at his sides. Oh, if he'd just been used this entire time, he was gonna—

"Hey! What're you doing here?!"

Sans let out another yelp as the sudden shout rang in his ears. He hastily cleared the image on the screen before turning to face the person who'd so fiercely addressed him.

"u-undyne! what, uhh… what do you mean? am i not supposed to be here or somethin'?"

Undyne set her hands against her hips, glaring down at the diminutive skeleton as though he should know the answer to that question. After a moment, she let out a sigh and looked away.

"Nah… I guess I just figured you'd be with Papyrus, is all."

"what..?" Sans asked, his brows furrowing. "isn't he supposed to be with you right now? he usually has his cooking lessons around this time of day, doesn't he?"

"Exactly!" Undyne replied, a bit of her usual ferocity returning to her demeanor. "I haven't seen that dweeb all day! He hasn't even come to give me his daily report! Papyrus is never late with his reports!"

Okay, now that was worrying. Acting a little strange was one thing, but skipping out on Undyne? That was truly unheard of. He cast a brief glance back at the monitor he'd been using a moment ago. He supposed his father's soul could wait a short while longer. He had to get this little distraction out of the way before he could fully concentrate on the more important task at hand.

The two of them immediately set off from Alphys's lab after that. Sans couldn't figure out a good way to ditch Undyne and head back home by himself, so he just let her follow as she wished. He didn't really care at this point. It was Papyrus they were going to check on, after all. He highly doubted that whatever was wrong with him was something he'd have particular interest in hiding from his brother's 'boss.'

They were in Snowdin soon enough, even though Sans still didn't have the energy for shortcuts. The skeleton led the way into the house, but it seemed untouched from when he'd left just an hour or so ago. That was odd… Papyrus had asked him to come home when he could, hadn't he? Unless…

Sans made his way upstairs, stopping in front of the door that was haphazardly decorated with police tape and warning signs. He gave the door a good solid knock.

"hey, papyrus? you in there, bro?"

There was a long moment in which nothing happened. So long, in fact, that Sans and Undyne were beginning to suspect that Papyrus wasn't in there after all. Finally, the door opened a tiny crack, a single dark eye socket peeking out at them. It glanced between the two of them for a moment, the sound of nervous fidgeting heard plainly from within. Suddenly, a long bony arm reached out and grabbed hold of Sans's hoody, pulling him inside before he really got a chance to react.

"S-SORRY, UNDYNE! SKELETON STUFF! NO FLESHIES ALLOWED!"

And the door was slammed shut in her face before any argument could be given.

Sans couldn't help but stare up at his younger brother as the taller skeleton braced his back against the door, as though his flimsy weight would be enough to keep the head of the Royal Guard from busting down the door if she really wanted to. If he didn't know better, he'd almost have to question if this was Papyrus at all. He wasn't wearing his 'battle body' for one, something that had practically become a living part of him ever since that costume party they'd attended. Furthermore, what he was wearing didn't exactly fit into the lanky skeleton's usual flamboyant style. He wore a plain orange turtle-neck sweater and a pair of long running shorts not unlike the ones Sans himself wore; black with a white stripe down the side. He couldn't remember the last time he'd seen his brother wearing something so subdued.

"uhh… nice digs, bro. you tryin' ta put together a new costume or somethin'? if so, I gotta say; velma wears a skirt, not shorts." he commented with a weak smirk, trying as usual to joke his way out of an uncomfortable situation.

"SANS, THIS ISN'T A TIME FOR JOKES!" Papyrus grumbled in reply. He then stepped away from the door to start pacing across the room a bit, his hands tugging nervously at the bottom of his sweater as though he were afraid it would ride up on him. "I… I THINK I MAY BE SICK OR SOMETHING…"

"sick..?" Sans repeated, his earlier concern returning to him. So much for joking it off. "what makes you say that?"

Papyrus fidgeted a bit more, hands wringing at the bottom of his sweater as he avoided making eye-contact with his elder brother. Finally, he drew in a deep breath, lifting his sweater up to expose his midriff.

Sans's jaw hung open in utter disbelief as he stared at his brother's abdomen. A glowing blue barrier stretched from the bottom of his ribcage to the top of his pelvis, sealing the area off from the outside world. Inside, right in the middle, floated a heart-shaped soul surrounded by a thick miasma of blue magic. He could barely make out the two distinct cracks in the surface of the pulsing cerulean heart; one long one towards the top, and a shorter one towards the bottom. Well, at least he'd solved the mystery of where Gaster's soul had gone to, though he now had to make one small addendum to an earlier statement of his; this was officially the weirdest situation he'd ever gotten himself into.

"you gotta be fuckin' kiddin' me…"