Something felt wrong back then. When Papyrus ran ahead to intercept the human on the path leading out of Snowdin, his self-assurance was that the kid would be completely fine with Papyrus. He wouldn't hurt a fly. His brother would never do anything to harm her. That was true.
So when Papyrus didn't return, he mustered up the energy to see them for himself. Via shortcut of course. But no one came. Rather he saw no one. Where else in the Underground would Papyrus wander off to?
One of the perks of being a skeleton monster was the fact that neither the cold nor the heat bothered him. In fact, what was temperature? He trudged through the narrow field of snow he knew they should be.
"Hey, bro! Where'd you run off to? I'm chilled to the bone here!"
Silence. Which was strange because Papyrus was never at a loss for words. The snowfall was obscuring his vision. Blizzards have great timing.
So he called out again.
"Come out! Hey! Pap! This isn't funny anymore!"
Nothing.
"Come on, you're starting to freak me out, bro! You win! So just get over here already!"
He wasn't used to speaking this loudly. It bothered him. So he kept walking forward, his hands in his pockets but his eyes searching for any telling indication.
Then he saw.
Snow. Dust. Snow and dust kicked together. And the only sign anyone had been there was a red scarf.
What did he do then? Nothing.
He watched her sing to Shyren, as kindly as she always acted. Under his hood, hidden by the lack of light in the Waterfalls, no one should have noticed him. But the kid did. That kind face changed so quickly.
Mocking. Him.
He wanted to kill her.
But that would mean going back on his promise. And probably never understanding why she did what she did.
"I guess that skeleton really wasn't all that great after all~"
Going back on the promise. Understanding why. Those words repeated like a mantra in his head. He almost lost it. Even though the bone of his jaw felt as if it were being ground away, still, he did nothing.
The child waited a moment. He realized she waiting for him. With no answer, she simply stated. "I don't know what I expected from someone who gave up a long time ago."
That one really threw him for a loop. He didn't stay to listen to anymore she had to offer.
He set aside his sentry post and his job. If he wanted to keep his promise, he would never see face again. Realistically speaking though, that wasn't going to happen. At first, Undyne tried to reach him, no doubt to set him straight for skipping out of work. But then suddenly, she stopped calling altogether, the day Papyrus didn't come over for his cooking lessons.
Instead, with his time, Sans brought back his old habits of deduction, speculating to himself about why she so suddenly changed her tune? She had been nothing short of kind. And now, the worst part was her mercy. She SPARED everyone. Every monster she encountered, regardless of how much she was hit, was left without a single scratch. Every monster she SPARED. Everyone except him.
There was something that struck him as strange about her. She walked like she knew the Underground. Looked as if she'd heard it all before. And made her journey straight to Asgore without a hitch. Long ago, he'd discussed the possibility of the existence of several alternate timelines with the Royal Scientist. Alphys wouldn't be able to comprehend. If these theoretical timelines existed, then there had to be a cause. Until now, he hadn't had an idea as to what that cause might possibly be.
So at judgment, he stood before the kid. And delivered his spiel. Without bringing in all of the questions he needed answers to.
"So. Uh."
Just one.
"If you've got some kind of special power... isn't it your responsibility to do the right thing?"
He eyeballed the kid with his left eye closed. What he searched for was more than a one word answer. Not a yes or no. He knew there was much to it than that. One more chance.
Tell me, kid. Give me a reason.
He stood in silence. She stood in silence. With that same innocuous expression.
Then her mouth spread wide into a horrifyingly remorseless smile.
"No."
After all his speculation, he thought nothing she she could possibly say would shake him, but that one word cut into him like a knife to his own soul.
He closed his eyes.
"Well. That's your opinion. I won't judge you for it."
Hate and burning disappointment rose to fill his empty chest, then his head, burning away his desire for closure and his willingness to accept a justification. When he opened his eyes again, it was as if he were seeing everything through a black-and-white screen–
...
Blue light sparked to life in his left eye, and Sans jerked awake, into his senses, now sitting nearly upright at his sentry station. Huh. He put his head down again. That was one hell of a bad dream. Not that he could remember it. Oh well.
Sans looked up and around. No one. In that case, he might as well should stay awake in the case Papyrus or Undyne ran over to check on him. Besides the unpleasant waking up, at least he got his nap, and he visited the lady behind the huge doors.
If a human ever comes through this door, could you please... please promise me something? Watch over them, and protect them, will you not?
The strangest request he'd ever heard. He hated making promises. And he didn't even know her name, but... someone who sincerely liked bad jokes had an integrity he couldn't say no to.
Frisk's hand hovered over MERCY.
Stubborn, aren't you?
After being SPARED, Froggit hopped away without a scratch.
Feeling good about yourself now?
Even though Chara's will relentlessly tried to throw her own aside, Frisk held strong. She kept walking forward, already past the last of the puzzles in the Ruins. She knew she would reach Toriel soon, praying no other monster would stumble into an encounter with her.
Another Froggit.
The black-and-white battle screen appeared before her once again, and she felt Chara forcing her way to the surface. There was no way she would let that happen. ACT. COMPLIMENT. Froggit didn't understand what she said, but it was flattered anyway.
You're starting to annoy me, Frisk. Chara snarled. What's with this whole MERCY act again?
Frisk ignored the second child in her head and kept walking. She'd had enough. This time, she was DETERMINED not to give in. Her cellphone rang as she walked into the next room. Toriel.
He felt something strange. It wasn't intuition. Maybe it was just that he was still disturbed by the bad dream he had earlier. Whatever it was. Remembering the promise he made earlier, he felt like going back to visit the lady. Something didn't feel right.
Still, Toriel blocked the way.
"What are you doing? What are you proving this way?"
Yeah, Frisk. What are you proving? That you can do what you want to do when you want? Congratulations! Chara mocked. Then she brought up the image of the toy knife in Frisk's possession. Just do it already. Kill her and save all that extra time for later.
"Fight me or leave!"
Kill her.
"Stop it."
Kill her.
"Stop looking at me like that."
Kill her. Kill her. Kill her. Kill her.
Frisk's thoughts filled with only those words, blocking out every other thought of her own. But she was DETERMINED. Chara had attacked her this way before. When she cut down Papyrus, she had absolutely no way to defending against the fallen child's strength. But now...
Frisk stood completely still, her eyes on Toriel, and Toriel had no idea of the deafening cacophony within the child's head. Her eyes gazed down on her with maternally.
"I know you want to go home, but... please go upstairs now. I promise I will take good care of you. We can have a good life here."
The second presence in her head suddenly went silent. Chara stopped her assault. Then. She laughed. The both of them knew every word Toriel would say. And that she would eventually give in.
"...It is sad that I cannot save the life of a single child."
Finally able to focus on the monster with the fallen child's silence, Frisk felt the urge to apologize to her.
"If you truly want to leave the ruins, I will not stop you."
Toriel's eyes dropped, and in that moment, Chara's will crashed into hers, breaking free.
Live with this, Frisk!
Frisk's body started into motion, the toy knife from earlier concealed in her hand. Toriel's eyes widened in surprise.
But instead, Frisk's arms embraced Toriel, quietly dropping the weapon. Her heart raced because now she knew that if even for a moment she let her guard down, Chara would shove her aside and take control. That was too close of call.
Chara was beyond frustration. Throwing a tantrum just like any other young child. You think that just 'cause only you can RESET that you're in control?! You're never gonna get rid of me! EVER! She was screaming in her head, absolutely furious, but that only made Frisk hold on tighter. Toriel knew nothing. And it was best that she should never know how close her body had been to becoming dust. So Frisk bore with the agony until Toriel walked away.
I'm gonna get you, you know. Sometime, you're gonna get tired of fighting me, and I'm just gonna do whatever I want.
She held her body weight against the door as the heavy brunt of the fallen child's anger nearly knocked her over, physically tangible. But she was DETERMINED.
Frisk steeled herself and pushed open the door "I'm the one in control."
His slippers crunched onto fresh snow in the deep forest. Shortcuts. Super convenient. His eyes focused on the huge doors just ahead. They were closed. Of course they were. He didn't know what he expected.
Crunch.
Now his eyes focused on the opposite direction.
Well. Would you look at that. A human. So the lady really did know what she was talking about. And was that... a child? Huh.
She was making slow progress, trudging through the snow with uncertain steps, but still she followed the clear path straight out of the deep woods. He decided it wouldn't be a good idea to shock her too much. Instead of the usual shortcut, he walked a good distance behind her as he planned how best to introduce himself.
Crack.
Whoops. Didn't mean to step on that. But she neither turned nor slowed, so he guessed she just didn't notice. So about that self-introduction...
The human stopped in her tracks. Just before the bridge.
"Sans."
The sound of his own name definitely took him by surprise.
Then she turned to face him. It really was a human. He'd never seen one this small before. She was even shorter than him. But what most stood out was the expression on her face. Her eyes were squinted, unfocused, and her entire body was trembling, but not from the cold. Though he'd definitely never met her before, any decent monster would be concerned about her well-being.
"Hey. You alright there, kid?"
At the sound of his voice, a smile pulled at the side of her mouth. But her quiet, clipped words stated something entirely different.
"Sans... Stop me."
It was like her entire body shut down.
"Whoa." The kid dropped just like that.
He caught her on her way to the frozen ground. Knocked out cold. It was obvious she wasn't gonna wake up soon and staying out in the snow probably wasn't any good for her either. What was she wearing? Just a sweater and pants? He never took off his jacket for anything, but this was good probable cause.
He stared at the small human in his arms in incredulity.
Well. Guess it was time to make good on his promise.