Sans wasn't in shock. He wasn't stunned or mildly disgusted.

He was shaken right to his core.

Where the glowing pink soul used to be was now a mass of blackened metal. It looked painful no doubt, and Sans could only guess what happened to make such a scar.

"Hey Mettaton… feelin' better?" He kept his voice soft and calm, not wanting to startle the poor creature next to Papyrus.

"Much… better… thank… you." His speech pattern was a little smoother, but shill sounded faint and grainy.

"Do you need anything?" The human was more than willing to help in any way they could.

"Battery…?" Sans could have face palmed. Of course he was out of power…

"Hold on pal. The kid and I'll go search the place for some power." Mettaton opened his top set of eyes a fraction.

"Thank… you… Sans…" Sans stopped in his tracks. If Mettaton remembered what happened to him, he would remember who did it to him, but he didn't seem afraid of this Sans.

The skeleton and the human (and the flower) all left the dark room and stopped at the fountain, none of them having any clue where to start their search. The human's stomach grumbled, and he remembered the Glamburger stand directly north of where they were.

"Come on kid. There might be something to salvage there." Sans tried to open the door, but found it held shut by something. He squared his shoulders and gave it a particularly strong shove, moving whatever was holding the door shut away.

Someone had barricaded the door with boxes, but judging by the pile of ash in the corner, it didn't do them much good. Sans remembered the poor sap that worked behind this very counter and felt a little nauseous. He slid a box over the ashes before the human saw.

They rummaged through some of the boxes, but the only thing they found was crumbs and napkins. Sans glanced at the other door and found it to be a freezer. The freezer was almost completely bare, except for a half-eaten box of bicicles.

"Hey kid, will this work?" It was obvious it wasn't what they were hoping for, but it was better than nothing. While the kid licked at the treat, Sans looked around for some kind of generator or battery or something.

There, tucked behind a pile of cardboard boxes, was a smallish container, about the size of a cooked turkey. It was black, with pink designs around it. There was an old note on top, the writing almost completely faded.

Dear Burgerpants~ please keep this behind here just in case! It was signed with a heart, and Sans knew exactly what it was.

"Come on kid! We found what we were looking for!" They made their way out of the burger place and back into the lobby. The air was still stagnant, but something made Sans' chest constrict with worry. He glanced around and tried to see if anything was out of place.

The fountain had an unbroken layer of dust, as did the carpet, except where they walked. There were six distinctive sets of footprints in the dust. Sans felt that same constricting in his chest, and for the first time realized he had never felt that before coming to this timeline.

If he didn't know any better, he would say someone was trying to warn him of something.

Sans did a quick headcount of the group and froze. He sprinted to the restaurant, almost forgetting about the kid behind him. They threw the door open and ran to the stage. Sans threw the battery at Papyrus.

"Hook him up and grab him. We're not alone here. We have to get out now." The reaction was immediate. Everyone began scrambling. Papyrus picked Mettaton up and holding him close to his chest and juggled the battery in his fingers. Sans grabbed the human by the wrist and pulled them aside.

He realized he would never be able to take everyone at once. He called to his brother and in three words told him the plan and flashed from the hotel. Sans tossed the human into a show poff and flashed back to get Undyne. It took another second to flash her back to her house.

Sans flashed back one last time to get his brother and felt the constriction in his chest. Something bad was going to happen. He made it back to the stage, only to find the room empty. His knees gave out for a second and he cried out,

"Papyrus?" His voice echoed through the room. Sans felt a bead of sweat slip down his skull and he tried again. "P-papyrus?"

Nothing. Sans jumped from the stage and ran to the lobby. A figure ducked behind the fountain, and Sans needed to make sure his brother was safe. He used his power to freeze the figure and lifted them into the air.

It was the monster child from Snowdin, Sans realized with a start. They were almost exactly the same as the one from his timeline, the only difference was a large scar running from their left eye to under their sweater.

"Let me go! Let me GO!" They finally noticed just who was holding them up. Their eyes grew wide and they bared their teeth. "It's you! Fight me you filthy sinner! I'll avenge Undyne if it's the last thing I do!"

"Calm down kid! I'm not gonna fight you." Sans' magic faltered as he heard a crash from the burger place. It wasn't much, but it was enough for the child to wriggle from the magic. They landed with a thump and jumped to their feet. Without any hesitation, they charged at Sans, nothing but fury in their eyes.

Sans scooped them back up again before they would trip on a bump in the carpeting. They floated a few inches above the ground, and was lowered down gently. They blinked once, twice, three times before turning to look at the skeleton.

"Be careful kid! You're going to get hurt if you don't watch out."

"Who are you?" Sans grinned wearily, really getting sick of that question.

"I'm Sans. Sans the Skeleton. It's a pleasure to meet you kid." He held a hand out in greeting, but realized the monster didn't have arms. He awkwardly let his hand drop to his side as the monster child gave him a sideways look.

"You're not Sans."

"I'm not… your Sans. It's a long story kid, but I'm not going to hurt you." The child narrowed their eyes with distrust. Sans held his hands up in a surrender gesture. "No really! I'm not the kind of guy to go around beating up kids."

"Why are you here?" The child's voice was still cold.

"I'm looking for my brother." In Sans' experience, it's best to tell as much as the truth as possible. "He's pretty tall, with spiky shoulders and a crack over his eye. He should be with a Robot?"

"I saw them…" Sans could have cried.

"Where? Where are they?" He took a step towards the monster child, who took three back in fear.

"Why should I tell you?" Sans stopped.

"You said you were going to avenge Undyne, didn't you? Why?"

"My parents were killed after you came to power. Undyne lied to the rest of the royal guard to protect me. I was going to help her in the rebellion but she was killed before we could join her cause. Now we have two reasons to keep going. Avenge Undyne and destroy Sans."

"We?" Sans knew he needed to find Papyrus, but this was just another piece in this confounding puzzle.

"Yeah. I have a small army behind me, and if I don't return to headquarters, they'll send someone to kill you guys."

"Wait kid… there's no reason to think about killing one another. What If I knew something that would change your world?" The child took a step forward, trying to be intimidating.

"What could you possibly know?"

"What if I told you where to find Undyne?" They narrowed their eyes and bared their fangs.

"Stop kidding around. She's been dusted."

"Tell me where my brother is and I'll tell you what I know." The monster kid paused, weighing their options. Sans could see it when they made up their mind when the emotions changed in their eyes, from cold anger to tentative belief.

"He took the robot and locked themselves in the burger place. I heard clicking and whirling. I don't know what he was doing though." He must have hooked Mettaton up to the battery and barricaded the door again.

"Oh thank god… they're safe…" Sans could literally feel a weight lifted from his chest as he turned to run to the burger stand. Just as he was about to take a step, something sharp caught his jacket and nicked his bottom rib.

Shouting some curses, he spun around and saw the child had a mouthful of his jacket and an angry look on their face. When they were positive Sans was going to stay, they spit out the fabric and took a step back.

"I told you what you want to know. Now, you tell me what I want to know." They had no mercy in their voice.

"Undyne is alive. She's at the rebellion base with a human." That was probably the last thing they expected to hear.

"What…?"

"You heard what I said. She's alive and still working on the rebellion. In fact, she'd probably be ecstatic to hear there are more for her cause. I'll take you to meet her, after I get my brother to safety." Sans waited for their response, itching to run to his brother.

"I'm going to go outside and report to my allies. If I come back and you're gone… you'll have an entire army out for your blood." Sans had to give it to them. For a monster that barely came up to his shoulders, they sure knew how to make a monster scared.

"I promise I'll still be here." Sans held his hand out again to seal his promise, and the monster child rubbed their head in his palm to seal it. They ran south, towards the door out, while Sans ran north, towards his brother.

"Papyrus let me in!" He banged on the door, only slightly desperate to make sure his brother was safe.

"Hold on Broth- Sans." Sans felt a twinge at the slip up, just another reminder that his wasn't this time line, this wasn't his brother. A faint scuffling sound came from behind the door and it opened a fraction. When Papyrus was sure Sans was the only one, he opened it enough for the stouter skeleton to slip through.

Mettaton was leaning up against the counter, his face calmer now that he was getting some power.

"Sans take Mettaton first. I will stay behind to watch out for whomever was following us."

"About that bro… they're with the rebellion. The kid thought Undyne had really been dusted, and took up the cause themselves. Apparently they have a small army." Papyrus just blinked at Sans. The shorter skeleton gave him a reassuring smile.

"I'll take Mettaton back now, but you have to wait by the fountain for when the kid comes back. I have to take them to see Undyne, and they can't think I left them here." Just as Papyrus was about to protest, Mettaton began to stir.

"Oh… hello Sans. Thank you for… helping untangle me. I had… all but given up believing I would be saved." He opened his eyes – all four of them – and gave Sans a sharp smile. He finally had some color in his metal cheeks.

"No problem Mettaton. Anything for a friend…" He hesitated, not wanting to bring up anything touchy when the robot was in such a frail state.

"What is it Sans?"

"I was just wondering why you didn't…" Sans scratched the top of his skull in embarrassment.

"Why didn't I mistake you as the… Underlord?" Sans felt his face light up with a thick blush and Mettaton gave a kind chuckle. "You are very… different. Part of my programing lets me see… the souls of monsters. Your soul is a… wonderful shade of blue. The Underlord's soul is… a corrupt red."

"Ready to go somewhere safe Mettaton?" The robot closed his eyes and smiled again.

"Yes… please let us leave this place." Sans lifted Mettaton much like Papyrus had, letting him held his battery in his lap.

"Bro I'll be right back, just stay out by the fountain." Papyrus nodded in affirmation and headed to the door. He had one hand on knob when Sans stopped him again. "Thanks bro. You really are the best. I can always count on you."

Papyrus froze so violently he crushed the door knob in his hand. His shoulders tensed and he let out a choked cry before quickly exiting. Sans hefted Mettaton to a more comfortable position and flashed to Undyne's house.

Sans placed Mettaton with his back to the counters in the kitchen and put his battery next to him. When he phased back into the kitchen, the human and Undyne jumped to their feet and rushed to the skeleton. He held up his hand to silence them.

"I'll explain in a second, but I have to go get Pap." Sans flashed back to the hotel, right next to his brother. He fell to his knees, gasping for breath. He almost never used his powers, and never this much at once. His whole body felt cold. Sans felt Papyrus kneel next to him and place a hand on his shoulder.

The door opened and the monster child slipped back into the lobby. They saw Sans on the ground and let a flash of concern across their face before putting back on a mask of indifference. They walked up to Sans and cleared their throat.

Sans looked up and saw them, and tried to stand. He ended up needing his brother's help to straighten up. Sweat beaded his forehead in the exertion.

"Sans… maybe it would be best for me to carry you the long way back." Sans shook his head and doubled over as the room spun. He let the world settle before grabbing Papyrus' wrist. Despite the fact he was about to pass out, he didn't miss how Papyrus flinched and leaned away from his touch. He used his other arm to scoop the monster child up and flashed back to Undyne's for hopefully the last time for a long while.

Sans collapsed the second they made it to the kitchen, dropping the monster child on their butt. His whole body convulsed as the sweat poured from his head. Sans had never known pain like this. It wasn't like the time Frisk went on their Genocide run and killed him, or the pain he felt when he realized his brother was gone.

"…rest…Sans…" A voice filled his skull, causing tears to drip into the tiles of the kitchen floor. His body convulsed again, his spine arching painfully backwards.

"G…aster-"

"You… burned… out… you… rest… then… continue… save… time…line…"

The voice faded as Sans' vision blacked out completely. One last thing got through Sans' blackness.

"BROTHER!"

I meant to update love yourself but I felt like doing this instead… I also should have been doing my English work. I have two essays to read and peer review as well as make up a 6-7 minutes speech for Tuesday… oh well…

Thank you everyone for the reviews, favorites and follows! I didn't know if anyone would like this headcannon for Underfell, but I honestly love the way this is coming out!

If you have any suggestions, leave a review or message me! I'm always willing to incorporate a reader's ideas into my stories!

Until next time

~Starlight