Wow, this chapter took me so long. Sorry if there are any grammar mistakes. I don't have a beta right now, but I'm planning to go over this chapter again with fresh eyes in a few days to make sure I didn't miss anything; however, I wanted to publish it now since it already took me longer than I thought it would. Please enjoy!

Insomnia

Part 4 (Sans's Nightmare)

As soon as Sans opened the door, Frisk's head snapped up from their crumpled position on the floor. Their face was stained with tears and their bed was disheveled from the fall. Frisk took a sharp intake of breath as they quickly scooted backwards, their elbow knocking against their nightstand in their panic. The table shook and the top-heavy lamp on the table began to sway. Sans reached out a hand, his magic steadying it just in time.

Sans's magic faded when he noticed the expression on the kid's face. Frisk's eyes were wide and their face was twisted into a look of terror. Sans raised a non-existent eyebrow at them. Surely the kid knew enough about monsters and magic by now that they shouldn't be surprised he had magic as well. Even if the kid didn't know, that didn't explain the look of fear.

Wait. That look on their face. Whatever it was, surprise wasn't the right word. In fact, there was a hint of recognition mixed in with the fear. Frisk had seen him use his magic before, but how was that possible?

"Careful kid, let's try to illuminate the situation," Sans joked absentmindedly as he tried to arrange his thoughts. "We shouldn't keep each other in the dark." There was no change in Frisk's expression. The kid just continued to stare at him with large, wet eyes. Man, it must have been one bad nightmare; the kid was shaking so hard it was like they were still half-living it. "No laugh?" Sans asked carefully. "Well, I guess you're right. It's not really the time for jokes. I heard you've been having a pretty bad time…"

Sans took a step forward and the kid recoiled instantly. Sans froze.

"H-hey now, kid… it's… it's alright," Sans assured them in the most calming voice he could muster. It was the voice he used to use when Papyrus got really upset as a kid. "It's alright, it's just me."

Tears continued to leak down Frisk's face as they let out a shuttering breath.

"Let me help you back on your bed, okay?" Sans asked, still not daring to come any closer.

Frisk didn't respond. Instead, they wrapped their arms tightly around their middle, as if they were trying to keep themself from falling apart.

"Frisk?" Sans asked again hesitantly. "Are you going to let me help you on your bed? All you have to do is nod, okay buddy? But if you need your space, I understand that too."

Frisk's eyes lowered to the carpet silently.

"It must have been one hell of a nightmare," Sans remarked while rubbing the back of his skull. He really wasn't good in these situations. He wished his brother was here. "But, uhh, you know I wouldn't hurt you, right kid? We're friends, aren't we?"

Slowly, almost imperceptibly, Frisk nodded; their eyes continuing to overflow with tears.

"Yeah, we're friends," Sans said with more reassurance. "Does that… does that mean I can come over?"

At first, Frisk didn't answer. Then, their silence was broken as their body wracked with sobs and they nodded once… and then again…. and again… Frisk continued to nod vigorously as they cried, their body shaking violently.

Sans sighed in relief. "You really gave me a scare there, kid." With careful movements Sans approached Frisk, but they didn't even seem to notice as they cried. "Here we go." Sans lifted Frisk up from under their armpits and placed them on the edge of their bed. Sans had thought about using his magic, but quickly decided against it. For some reason, that seemed to freak Frisk out more.

Sans sat on the bed next to Frisk with a bony hand on their back as their sobs continued. They sat together in the quiet room for a long time with Sans rubbing their back soothingly.

Eventually, Frisk's sobs subsided and they lapsed back into their tearful silence. They stared at their hands in their lap, occasionally taking a shuttering breath.

Sans let out a small breath of his own. "Listen, Frisk, I know you've been through a lot, but I want you to know you can talk to me. I'm not going to judge you, well... not more than I already have, but you already passed that test with flying colors." His grin was not returned, but he didn't expect it to be.

"Those nightmares of yours seem to be pretty bad," Sans continued. "It might help if you talked about them. It might make them seem less scary." There was no movement from Frisk; only frozen silence. "As bad as your nightmares are, you know they're not real-"

"You're wrong," Frisk whispered with a hoarse, empty voice.

"Huh?"

"You're wrong," Frisk said again, more determined. "They are real."

Sans just stared at them for a moment. "Frisk, you know dreams aren't-"

"They're not dreams," Frisk said, closing their eyes. "They're memories."

Ah. So, Toriel had been right. Sans let out a soft sigh. "Frisk, in your dreams are you reliving battles you had in the Underground? Like the ones you had against Undyne and Papyrus?"

Frisk nodded and swallowed thickly.

"Y-yeah-" their voice cracked as a few stray tears ran down their face. "And you."

Sans stilled. "Huh? What are you talking about, Frisk? We never fought."

Frisk paused indecisively before slowly pulling their feet up onto the bed and hugging their knees close to their chest. They muttered something into the fabric of their pajama pants that Sans barely caught, and when he heard it, he wished he hadn't.

"Not in this timeline," Frisk muttered weakly.

Sans froze, and then slowly, his hand fell from Frisk's back. He stared at the small child, a chill running up his spine.

"Wh-what?" He asked, his voice hitching slightly.

Frisk didn't look at him as they hugged their knees tighter.

"I- I didn't understand at first," Frisk said, their voice trembling. They stared down at their knees, refusing to look at Sans. "In my dream everyone kept dying and it was all my fault. It-it was so horrible," Frisk sobbed as they leaned their forehead against their knees. "I didn't understand why I was having these dreams, but now I get it. They're real. They really happened and y-you know about them too. You've known about the different timelines for a long time."

"Kid…" Sans breathed, but he didn't know what to say. What did this mean? He always told himself that the murderous Frisk from his dreams, and this one, had to be completely different people. He didn't understand why there were two different Frisk, but there was no way this innocent kid was capable of the evil that the other Frisk was. In order to love Frisk as he did, Sans had to believe that.

"You must hate me," Frisk said in a hushed tone. "You must hate me so much. It's my fault Papyrus died, and Undyne and m-mom, a-and you."

Sans stared at the kid with dread. Why was Frisk saying it was their fault? His Frisk didn't play any part in the bad timeline. His Frisk wasn't capable of that.

…Right?

There was so much Sans still didn't understand, and for the first time an in a long time, Sans was curious, and like the scientist he is, well, was, Sans needed to know everything. Now that Frisk remembered the different timelines, Sans might finally begin to piece together the mystery of the anomaly before him. There was so much he had to ask. Why did they keep resetting? Why was there an evil Frisk that killed everyone?

Sans was about to ask, to finally get the answers he never thought he would, when he caught the look of agony on Frisk's face. Sans's core, the heart of his magic, felt like it was breaking into tiny pieces as he watched the kid cry.

Long overdue answers could wait a bit longer.

Without really thinking about what he was doing, Sans scooped up the crying Frisk into his arms and hugged them tightly again his chest. Frisk had startled at first before sinking into the folds of his jacket, turning their face into the fabric as they continued to cry.

"Hate you?" Sans asked softly as he gave them a gentle squeeze. "Does it seem like I hate you, buddy?"

Slowly, Frisk shook their head back and forth as they clung to his jacket.

"I had no idea you remembered so much from the other timelines," Sans said quietly. "They must have been really scary to watch."

Frisk's whole body was shaking in his arms and Sans held on a little tighter.

"You're right about one thing," Sans continued. "I do hate that human that killed everyone, and I know they look like you, but I also know they're not you. You're not capable of that stuff. You love Paprus, and Tori and Undyne. You would never hurt them. I know this, because if you didn't love them, those dreams wouldn't upset you, right?"

His words seemed to have helped somehow, because Frisk managed to take a few shaky breaths between their sobs, and the shaking began to subside.

Sans let out a short, humorless laugh. "No wonder you were freaked out by my magic. You must have seen me kill that other Frisk so many times..."

Sans felt Frisk tense in his arms. "I- I'm sorry," Frisk mumbled through the fabric.

"Aw, kid. You don't have anything to apologize for. I'm the one that's sorry you had to see that. You know that I wouldn't hurt you, right?"

The question brought on another fresh batch of sobs from the kid, but to Sans's immense relief, he felt Frisk nod into his chest.

Sans rubbed the kids back as he waited for them to let it all out. Sans knew kids cried, it was a part of life, but no kid should be made to cry like this. Frisk wasn't just sad, they were scared, and confused and more traumatized than anyone, especially not a kid, should ever be. Frisk had been attacked by almost every monster they ran into in the underground, but despite how scary that must have been, Frisk had never broken down like this.

Sans looked down at the kid and stroked their hair. The kid was so brave and had done so much for them. It wasn't fair. Why did Frisk have to see that other timeline? They didn't deserve to be subjected to that. They deserved to be happy, at least until they reset the world again.

Heh.

Who would have thought it? The anomaly, the thing that kept resetting, the thing that made everything he did completely meaningless, was actually a little kid that Sans deeply cared for. How did the one who made everything meaningless find a way to add meaning into his life? If that wasn't a paradox, Sans didn't know what was.

Frisk's crying began to subside into tiny hiccups, and Sans's shoulders sagged in relief. He was starting to worry the kid wouldn't ever stop.

They sat in silence for a bit as the kid shivered from exhaustion. The kid's face was still buried in his jacket as if they were still trying to block out all the bad memories with just a few pieces of fabric.

"Feel any better?" Sans asked while looking down at the kid in his arms.

"A… a little," Frisk mumbled into the fabric, their voice hollow and distant. Sans winced. They didn't sound any better. He was relieved they weren't crying anymore, but this wasn't much of an improvement.

"That's good. I was worried you might have cried your eyeballs out," Sans said, feigning a serious tone. "Let me check and make sure they're still there."

Frisk let out a small muffled sound and shook their head, their face still hidden from view.

"Come on, kid, let me check. What's Tori going to say if she finds out you lost your eyeballs, huh?"

A light bubbly sound filled the air as Frisk started to giggle. "I still have my eyeballs, Sans!" they protested.

"How do you know, huh, kid? When was the last time you checked?"

"I just know!" Frisk was laughing now as they buried their face deeper in his jacket.

"That's what someone who lost their eyeballs would say! Well, I guess I have no choice."

"Ahh! San! That tickles!" Frisk squealed as they attempted to block Sans from tickling their stomach, but to no avail. "Okay, okay!" they said breathlessly as they laughed. They lifted their head up to look at Sans and he stopped.

"Oh, look at those peepers," Sans said with a large grin. "I'm ex-eye-ted they're still there. Now we can see eye-to-eye, so to speak. "

Frisk giggled again, their grin spread wide across their face, just where it belonged.

"See what I did there? Because eye did." Sans winked at them. "What? Too cornea?"

Frisk continued to laugh and Sans chuckled.

"There we go, that's much better," he said in approval as he gave the kid a comforting squeeze.

Still smiling, Frisk leaded the side of their head on Sans's jacket, but didn't burry their face in it this time.

"Sans?"

"Yeah, kid?"

There was a long pause and Sans looked down at them in concern.

"How…" Frisk continued slowly, their brow furrowed in confusion. "How come you can remember stuff from the other timelines but nobody else does?"

Sans sighed and shifted the kid in his arms so they were laying more comfortingly on him. "I don't. Not really. I have dreams, just like you, but because I knew about the existence of other timelines I knew the dreams were real. It seems the longer I stay in a timeline the more dreams I start to have, but when everything resets, I forget everything just like everyone else."

"Do you think anyone else will start to remember?" Frisk asked fearfully.

"I hope not, kid. At least, not more than they already do."

Frisk lifted their head up to look at Sans. "What do you mean?"

"Hmm… how do I put this?" Sans knew he didn't have to dumb things down for the little time traveler, but the nuances of timeline jumping wasn't easy to explain, even to the cleverest of audiences. "Through all the timelines was there ever a time where someone seemed to remember something that they shouldn't? Maybe you look familiar to someone you haven't met yet, or they remembered something you haven't said? Papyrus will sometimes remember jokes that I haven't told him, but insist I have. The timelines seep through sometimes and things aren't always forgotten."

"So… even though the world reset, all that bad stuff still happened?"

Sans head snapped down to look at Frisk in concern. He could hear the tears in Frisk's voice, and the last thing he wanted was for them to start crying again.

"Come on, kid, look at me a sec."

Frisk complied, their eyes glossy with tears.

"It happened, and at the same time, it didn't happen," Sans tried to explain. "I know that doesn't make much sense, and I know it's hard to understand, but you need to remember that this is the timeline you're in. Right here, right now, everyone is alive. You can't get muddled down in other timelines. You have to think about what's happening now. Doesn't that make sense?" Sans wanted to laugh at the irony of it all. He wasn't the most qualified person to give a pep talk about not letting other timelines get to you. Irony was one of his least favorite types of humor, and yet, it seemed to haunt his life.

Frisk nodded solemnly. "I think so." They bit their lip before looking down at their hands, which were still clinging to San's jacket. "Fighting you in my nightmares scared me a lot," Frisk admitted quietly. "Do you… do you have nightmares about me too?"

When Sans didn't answer, Frisk looked up at him worriedly. "Sans?"

"Uh, yeah, I guess, kid," Sans answered gruffly, with a smile plastered on his face but this time his smile was much harder to maintain than usual. "I guess we're both going to have nightmares about each other for a while."

"Sans… The one that kills everyone in the bad timeline, they look exactly like me."

Frisk lapsed into silence just long enough for Sans to get concerned. Where was Frisk going with this?

"After your nightmares you…" Frisk continued slowly, "you probably don't want to see me very much, do you?"

Sans ruffled the top of Frisk's hair playfully in an attempt to lighten the mood. "Whatcha talking about? I always wanna see you, kid."

Startled, Frisk looked up at Sans, but then their eyes narrowed suspiciously. "I'm serious, Sans!"

Sans laughed. "Funny, I thought you were Frisk?"

Frisk continued to glare at him. "Why do you do that? Why do you always make everything a joke?" they complained loudly.

Sans wasn't used to being called out on his usual avoidance tactics, but he wasn't entirely surprised by this either. Frisk was the only person who didn't fall for San's usual misdirection. Sans rarely outright lied, but no one suspected anything from the guy whose highlight of their day was making an outrageous pun. Humor really was the best way to hide. Too bad the kid never fell for it.

"It's just- I don't understand! How can you even stand to be friends with me?" Frisk asked, their shaking voice bordering on hysterics.

Sans's eye sockets widened in surprise.

"I must always remind you of-of-"

"Whoa, hold on their kid," Sans interrupted quickly, their hand cupping the kid's face before they could bury it in his jacket again. "You're getting a little carried away. Okay, you're right, I wasn't taking your question seriously, and I'm sorry. But you gotta understand, the reason I didn't take it seriously is because it sounded like a joke to me."

"Huh? What do you mean?" Sans used a bony finger to wipe the tears from Frisk's cheeks.

"You asked if I sometimes don't want to see you because seeing you would remind me of that bad timeline. I gotta tell you kid, that's the most ridiculous thing I've ever heard."

"I don't understand."

"The truth is, kid, the Frisk from that timeline is so different from you, that I don't even think they're human," Sans explained. "It's not a monster or a human, it's just a thing that's wants to kill everyone just because it can. It's so angry and empty. It doesn't care if you plead with it, or show it kindness. It doesn't understand mercy. If you show it friendship, it will strike you down, just like it did to- to my brother-" San's cleared his throat, but the tightness didn't go away. "It killed everyone that stood in its way, just because it could. And because if it's determination, it never stops, and nothing can stop it. It- its wrong. It's evil, and it shouldn't ever have exited. It-"

Frisk made a panicked sound and Sans looked down at them in alarm. Frisk was starting at him with wide, frightened eyes.

"Shit, sorry kid," Sans apologized quickly as he covered his glowing, blue eye with his hand as he took a breath to calm himself down. "I just got myself worked up. I didn't mean to scare you."

Frisk was staring up at him, still rigid with fear, and Sans mentally cursed himself. The kid was having nightmares about his battle with the things that looked like Frisk, and now he was just making it worse. He had killed that evil Frisk over and over again and his Frisk had to experience that too. He couldn't imagine what the kid thought of him now.

Slowly, Frisk's muscles began to relax and they reached out to grab the hand covering Sans's eye. Sans tried to resist at first, knowing his eye was still burning bright blue, but the kid was insistent. Finally, Sans allowed them to pull his hand away.

Frisk didn't even flinch this time as they smiled up at him. Overwhelmed by the amazing, brave little kid in his arms, Sans pulled them into a hug.

Sans didn't let go as he continued his explanation. "My point was, kid. Even though you have the same face as that creature, you don't resemble them at all. You feel things other than anger, you laugh at my jokes and you let me stack hotdogs on your head." Sans chuckled as he pulled away to look down at the kid, his eye back to normal.

Frisk watched him silently, a small smile beginning to crawl across their face.

"I like seeing you after I have those dreams, Frisk. It reminds me that I'm in the right timeline. You're nothing like that creature… whatever it is."

Frisk sighed and leaned into him. "Chara."

"What- what was that?"

"They're name. The one that kills everyone in that timeline. Their name is Chara."

Sans stared down at the kid, his hold on them going rigid.

"You wanna fill me in, pal?" He tried to sound casual but the tension in his voice gave him away. "I've spent a good portion of my life dedicated to learning about the anomaly, but it sounds like you've got it all figured out."

And so, Frisk told the story of Chara and Asriel. Frisk recounted their nightmare and explained how Chara had been controlling them in the bad timeline. Their face scrunched up as they struggled to fill in the gaps they didn't understand. Sans noticed Frisk skipped over talking about the murders Chara made them do, but Sans didn't comment. It wasn't something he wanted to be reminded of either.

Frisk talked about Alphy's experiments and how the experiment had unintentionally saved Asriel's life, but not his soul. They explained how in the end Asriel had destroyed the barrier and set the monsters free. Sans noticed that Frisk talked as if they had known Chara and Asriel for a long still seemed shaken talking about Chara; as if whispering their name would somehow bring them back to life, but when Frisk talked about Asriel, despite what Flowey had put them through, it was as if Frisk had been talking about a long lost brother.

When Frisk finished the story, the room filled with a heavy silence. The only sound was Frisk shifting on San's lap, their eyes fixated on their hands as they waited for Sans's reaction.

"Wow, kid," Sans said at last. "I don't know what to say." Sans paused as he tried to gather his racing thoughts. After all these years, he finally learned the truth. "I guess that's why you didn't tell us how the barrier was destroyed."

Frisk fidgeted in his lap again. "I-I didn't want to tell mom and Asgore about Asriel. It would only make them sad. And… I don't think Asriel wants them to know either."

Sans nodded. "Yeah, I think we should keep this between us, but thanks for telling me, kid."

"You deserve to know why things kept resetting," Frisk said quietly.

Frisk let out a small squeak as Sans picked them up off his lap. He laid down on the bed, placing Frisk on his ribcage with their head resting on his collarbone. Frisk shifted only once to get comfortable and then let out a contented sigh as Sans wrapped his arms around them.

"I thought you were the only anomaly, kid," Sans said mostly to himself, "but it turns out there were two. I guess when you fell down into the underground your determination trumped Flowey's and took away his ability to reset. But I have one question." Frisk lifted their head to look at him. "When you first started telling me about all this stuff, you said everything was your fault. If you knew it was really Chara hurting people, then tell me kid, why would you say that?"

Frisk shrugged and looked away.

"Come on, kid, you can tell me," Sans encouraged softly.

When Frisk looked back up at Sans, their eyes were brimming with tears. "Because… because in some of the timelines, Chara doesn't kill everyone. I think maybe… I have some control? If I could do that in some timelines, then it's my fault that I allowed Chara to kill everyone in the bad timeline. It's- it's still my fault."

Sans let out a breath. "Ah. I see." He paused for a moment before saying slowly, "I'm… I'm glad you told me that."

Frisk bit their lip to keep from crying as they nodded their head.

"But now I've got something to tell you."

Frisk wiped the tears from their eyes with the sleeve of their pajamas. "What?"

"Knock knock."

Hesitantly, Frisk looked down at from their position on his ribcage. "Who's there?" they asked meekly.

Sans grin widened. "Thank."

"…Thank who?"

"Thank you, Frisk, for… for being strong enough to beat Chara in this timeline, and for keeping my brother safe, and for freeing us. I owe you one, kid. We all do."

Frisk's eyes filled with fresh tears, but this time, Frisk was smiling as they attempted to hug as much as San's large frame they could with their tiny arms. Sans hugged them back as tight as he dared.

"None of this is your fault, Frisk," Sans whispered. "I promise, it's not your fault, and I'm so… so proud of you."

Frisk's breath hitched in their throat as their shoulders began to shake. Sans rubbed their back soothing as they cried.

Minutes passed between them, but Sans barely noticed them. He found stroking Frisk's hair seemed to have the most calming effect on them, and eventually the tears stopped and Frisk's breathing began to slow. He thought the kid had fallen asleep when he heard a little voice say his name.

"Sans?"

He looked up to see a tear-stained determined face starting straight at him. "Yeah, kid?"

"I wanted to tell you… I'm not going to reset anymore, I promise. Everything will be okay now." Frisk reached over and touched the side of his skull. "So please… please don't be sad anymore."

San's chest lurched. "I…" Sans began, but the rest of his words were caught in his non-existent throat. He found himself unable to hold the kid's pleading gaze as he looked away. "Heh. Don't you know the rules for promises, kid?"

"What rule?" Frisk asked innocently.

Sans removed the tiny hand from his face, squeezed it gently, and looked back up at the kid. "Don't make ones you can't keep."

It had come out harsher than he intended if Frisk's wide-eyed and hurt expression was anything to go by, but he couldn't take it back now.

He used to think that if the anomaly ever promised him there would be no more resets everything would change. He would finally be able to care about things again and move on with his life, but instead, he just felt like Frisk's words were just a punchline to the bad joke that was his life. Not that it was Frisk's fault. None of this was.

He just couldn't bring himself to believe Frisk's promise only to wake up one morning with snow outside his window and cave ceiling for a sky. Even if he wouldn't remember the other timelines right away, he eventually would. It hurt more to keep on hoping and Sans was so tired of being in pain.

He couldn't bring himself to believe in a happy ending, or any ending for that matter.

Seeing Frisk's troubled face, Sans ruffled their hair playfully. "Okay, kid, time to get some sleep. We can keep each other's nightmares away, how does that sound?"

"O-okay, I guess..." Frisk faltered. They looked like they wanted to say something more, but decided against it. Eventually, Frisk settled on another question. "Will you stay with me all night?" they asked with pleading eyes.

Sans laughed. "Are you kidding? I've already laid down, of course I'm not getting back up!"

Frisk smiled weakly. "Good night, Sans. Sweet dreams."

"You too, kiddo."

It was the sun that woke Toriel, not Sans like they agreed. Toriel looked to her right, expecting to see Sans asleep on the couch next to her only to find that she was alone.

Toriel climbed the stairs as fast as she could. How many times had Frisk woken up from a nightmare with no one there to comfort them? Had Sans been able to talk to Frisk at all? Where did he go? It was still early in the morning and it was likely he was asleep somewhere. She was going to have a few choice words with him when she saw him next.

Toriel opened the door to Frisk's room and had to clamp a hand over her mouth to keep herself from cooing at the adorable sight.

There was Frisk curled up happily on top of Sans, sleeping more peacefully than Toriel had seen them sleep in the past week. Sans, who was snoring softly, had their arms wrapped around Frisk tightly. Toriel wasn't sure she could pull Frisk from him if she tried.

Toriel approached the two sleepers and pulled Frisk's blanket over the two of them, tucking them in gently. She didn't know how Sans did it, but she was glad she asked for his help. She had always sensed there was some sort of bond between Frisk and Sans that went deeper than she could understand.

Toriel knew there were things that Sans didn't tell her, and that was fine, but sometimes Toriel felt like she barely knew him. He doesn't talk about his interests, or what he used to do before moving to Snowdin. He seemed happy, but sometimes that happiness didn't feel genuine. When they talked, Sans only talk about his brother and made hilarious jokes to get her to laugh. That was about it. Sometimes it felt like Sans was living more for his brother than for himself, and Toriel couldn't help but worry about him.

But whatever the reason why Sans was keeping her at a distance, at least he was slowly letting one more person into his life. Although, truth be told, Frisk could get under anyone's skin, even if they didn't have any.

I hope you enjoyed this. This is the chapter I've been really looking forward to getting out. Since this is a series of oneshots this is the perfect time to put in any requests! I need ideas for oneshots so please review and if you have an idea let me know! I'll try to do it if I can.