A/N: After getting some useful feedback, I decided to revise the chapter a little. It's nothing crucial, but I recommend re-reading it before the upcoming one.

Splash.

"NYEH!"

Splash, splash.

"OF COURSE I KNOW THE SOLUTION TO THIS PUZZLE, HUMAN! AS WITH EVERY WELL-DESIGNED DEATH TRAP, TIMING IS KEY!"

Papyrus' booming voice is drifting toward you over the ever-present rush of water, amplified by the echo of the caverns. You're sitting behind the field of tall sea-grass in the next room, your feet dangling over the precipice. Hearing your brother's obvious enthusiasm about traveling with the kid does nothing to improve your mood, but you have to make sure you're present at the first confrontation with Undyne.

"IT GOES EXACTLY LIKE… THIS!"

A few quick splashes later, you hear the dull thud of a boot meeting with solid ground, closely followed by the other.

"NYEH HEH HEH! A SIMPLE ROCK PUZZLE IS NO MATCH FOR MY GREAT INTELLECT AND ALL-ENCOMPASSING KNOWLEDGE!"

He always liked this one, you muse. He had to go through it so many times when visiting Undyne, he could probably do it in his sleep. He even tried to entice you to do it once or twice, but you insisted that teleporting to the other side counts as a legitimate solution.

"FEAR NOT, HUMAN! JUST FOLLOW IN MY FOOTSTEPS, AND NO HARM WILL COME TO YOU!"

You feel a pang of jealousy. Your brother sounds more carefree and cheerful than he's ever been in a long time. He clearly enjoys the kid's company. They make him happy.

"W-WOWIE! IT'S ALMOST LIKE YOU KNOW THIS PUZZLE AS WELL AS I DO! OR MAYBE - WAIT, WHAT ARE YOU DOING?"

Maybe happier than you ever could.

"OH! I MUST SAY, THIS WORN, CRUMPLED, MOTH-EATEN TUTU IS A GREAT CHOICE, HUMAN! IT DEFINITELY SHOWS OFF YOUR PERSONALITY!"

You can't hear Frisk's tiny footsteps at all, but the soft squelching sounds made by the water stuck in Papyrus' boots are definitely coming closer. You reluctantly get up and look for the familiar armor-clad figure half-hidden in the darkness among the stalagmites. A cold flash of light on metal catches your eye, and it's so familiar, so, so familiar by now that it makes you shudder.

There she is, right on cue.

The heroine.

The most determined of you all.

Or, more precisely, who used to be the most determined.

"You're gonna have to try a little harder than THAT."

She was -

You squeeze your fists in your pockets to push the memories down, back into the deepest recesses of your soul. As quiet as you can, you edge closer to the patch of grass. You hope that even if she does spot you, she will be too preoccupied with the kid to pay any attention to the most useless sentry under her command.

Not even a minute has gone by when Undyne tenses up; she soundlessly summons a spear in her hand and moves closer to the cliff's edge. She must have made some noise though because all of a sudden, Papyrus' footsteps stop.

"UHH…"

The fish monster swiftly retreats from the edge, her spear vanishing immediately, but it's too late already.

"WH-WHAT? NO, THERE'S NOTHING WRONG, HUMAN! NOTHING AT ALL! IT'S JUST THAT I SUDDENLY REMEMBERED SOMETHING OF THE UTMOST IMPORTANCE! SOMETHING THAT I HAVE TO TAKE CARE OF RIGHT NOW! YEAH! SO, UMM, IF YOU'D EXCUSE ME..."

Of course he wants Undyne to let the human live. Of course he wants everyone to be friends.

What enviable nativeté.

"DON'T WORRY! I'LL BE BACK BEFORE YOU CAN COUNT TO TWELWETY ZILLION! OR ANOTHER IMPROBABLY HIGH NUMBER I JUST CONVENIENTLY MADE UP!"

Before Frisk could say anything, your brother leaves in a hurry in the direction of the puzzle room, probably to climb up and try to talk with the captain. You wait a minute to make sure he can no longer hear you, then peek around the grassy patch. The kid has sat down at the edge, a sharp pebble in their hand, idly making some doodles in the dirt. They are clearly not afraid of Undyne at this point.

With some difficulty, you manage to push through the sea-grass and come out in the open. Frisk looks up and immediately scrambles to their feet. They wince for a moment as if they were in pain. You ignore it.

"heya."

"Sans! Where were you?"

"around," you shrug airily. "i even heard some breaking news, buddy. a little bird told me while carrying me over a disproportionately small gap that you convinced my brother to play bodyguard to you."

They fall silent once again, nodding. They don't look away though, staring you straight in the eyesockets.

Playing brave, huh.

"looks like we're on the same page, then," you say, putting on your coldest grin. "except this isn't how it works, kiddo. we made a deal. remember? or are you so used to break your so-called promises that you can't even be bothered to keep them in mind?"

"I - I didn't make any promise about Papyrus," they stammer.

"well then. now's the time for making it. what do you say - pal?"

"No." Frisk shakes their head, their expression stubborn. "You're hurting him, you don't even realize how much. And you're hurting yourself too." They stick their chin up in the air. "If you want to hide and stay out of it, then hide. It's your decision."

"i think you didn't understand me, kid," you growl. "send papyrus home and never talk to him again. now."

"Do it yourself."

"i'm saying it for the last time, brat." You feel rage building up in your soul, burning you, eating you alive. You step closer, your eyelights going out. "Leave my brother alone."

Frisk gasps, staggers for a moment as if they were feeling queasy, and doubles over, wheezing. You barely have enough time to get concerned when they lift their head and look back up to you, smiling.

Even in the dim light of the caverns, you can clearly see the deep red of their eyes.

„What is it, Sans?" you hear the mocking voice of Chara once again. "Are you afraid I'll steal your EXP you might gain from killing him?"

They don't have time to react. You grab their soul and squeeze it, hard. The child cries out and falls to their knees, clutching their chest, but you can't restrain yourself, and you don't want to. You've been wanting to do this for a long time. To who, you don't even know anymore.

They both deserve it. They both deserve it, no matter what they -

"LET THE HUMAN GO!"

A long white bone whooshes through the air and severs your connection to the soul. You jerk back in surprise, nearly falling over.

"SANS!"

You turn back. Papyrus is standing at the far end of the cliffside, his scarf billowing, a few bones floating around him in the air, ready to be launched. His expression speaks of incredulity and sorrow. You feel your marrow go cold. He shouldn't have seen you. You shouldn't have gone near him.

You had one job, idiot...

"BROTHER! WHAT ARE YOU DOING? THEY ARE MY FRIEND!"

You're staring back at him dumbly, not knowing what to say. Your hands are trembling, and you struggle to summon your magic to make a shortcut. You must leave right now. You must.

Do I -

Do I have to -

I want to -

Papyrus waves a gloved hand, making the bones disappear. He makes a hesitant step toward you, his voice softer.

"SANS, IT'S OKAY. I'M NOT ANGRY, I'M JUST -"

"no."

You must.

"SANS, WAIT -"

You finally snap your fingers and leave without looking back.

The secret grotto looks the same as the last time, except instead of your screams, the echo flowers are whispering among each other, repeating a secret wish a monster made upon the stars of the Underground not too long ago. The hushed, shy voice sounds almost too afraid to express what they are longing for.

"I… I just wish that n-no harm would c-come to… to her... p-please..."

Alphys. Undyne's greatest fan. A coward by day, a warrior after the darkness has fallen.

She put up a fight you'd never expected.

They all did. They summoned every drop of their strength to stop you.

You're hiding again. Hiding from the monster you once thought you loved more than anything. Hiding from the child who you made a promise to. A pathetic lie if you ever told one.

Exhausted, you lie down on the bench, closing your eyesockets. Maybe you can catch some sleep while you're at it. Maybe you can forget all of this for a little while.

There's nothing sweeter than unconsciousness...

After half an hour or so, you finally give up and set out to destroy the first save point in the area. The kid must have passed the grass room long ago, and Papyrus is going to make a good job of protecting them, anyway.

You pop up at your sentry station, startling the red newt monster (you never bothered to remember their name) who, as usual, is standing next to the lonely echo flower, waiting patiently for someone who they can explain the flower's purpose to. He gives you a funny look when he sees you grabbing the air next to the snow-covered stall, but you couldn't care less. You squeeze your fist as hard as you can, prepared for some heavy resistance, but the star, after shivering for a moment, immediately crumbles into dust. You quirk an eyebrow.

...Huh.

That was easier than you had expected. Maybe you just had to get the hang of it again?

Or maybe you just had to give in to your long-repressed emotions. Who knows.

In any case, time to take a look at where the kid is right now. Preferably without them spotting you. There's no point in teleporting all over the area without knowing their exact location, so you decide to follow them on foot, your pace a little faster than the usual (a pretty low bar to clear, to be honest). You scramble through the field of sea-grass again, sweeping a few stray strands off your hoodie, when something makes you stop dead in your tracks.

The save point isn't there.

What.

This cannot be. It cannot not be there. It was clearly there just half an hour ago; you've seen it pulsing nearby when waiting for Undyne. Now, though, you see only the empty cliffside, devoid of any light.

What the hell.

You stand in front of the stony surface, gawking at the empty space where the floating star should be. You feel around with your hands in the air, hoping beyond all hope that maybe you just can't see it for some mysterious reason.

Nothing. There's nothing. It has vanished without a trace.

You sit down, still staring at the cliffside incredulously. You must be hallucinating. Why would a save point disappear into thin air?

Did… did that damn flower do something to it? But why would he do such a thing?

You scratch your chin, feeling stupid.

Maybe it moved into another room?

But of course. Save points are now wandering all over the place.

You let out a snicker at the absurdity of the idea, and -

- and your grin falters.

There's no save point.

There's... no save point.

A foreboding chill is spreading in your ribcage, as if all of a sudden, a cube of ice had replaced your soul.

There's no way the kid could have reached the end of Ferry Dock yet. There's no way they could have reached the next save point at the mousehole. There's no way.

Which means…

Which means they currently have nowhere to return to if they die.

Your pupils shrink into pinpricks.

FUCK.

You must intervene before Undyne can catch up to them. You must make sure they get to the next safe haven in one piece. You're certain Papyrus will do his best to protect their companion, but there's no way of knowing if he would be there with them at the time. Being all-too familiar with Undyne's rather intimidating ways, she could have convinced your brother eventually to mind his own business. It's up to you, unfortunately. Stalling the fish monster won't be the easiest task, but you must buy some time for the kid, even if it means taking some verbal bashing from your alleged boss.

Provided you didn't screw this up permanently.

You take some deep breaths, mentally preparing for the inevitable ruckus to come, and snap two shaky fingers together. Space warps around you, and in the next moment, something blue and shiny whooshes right past your skull as you nearly get impaled by a spear.

"AAH! WHAT THE -"

A harsh metallic clang tears through the air as Undyne barely avoids tripping over you. She jerks back in surprise, slipping on the wet planks, her attack going astray. You hear the loud thumps of someone running on the far side of the dock, and as you look over your shoulder, you can see Frisk sprinting away.

Okay. Just in time. I can do this.

Undyne gathers herself and tries to make chase, barely even looking at you, but you quickly block the way, hands in pockets.

"Whuh?!"

"'sup, undyne?"

"What do you mean, 'sup'?!" she shouts in your face. "Get out of my way, Sans! NOW!"

"hmm… why?"

"The human! They're getting away right as we speak! Stand aside or I swear I'm going to push you into the water!"

"good. i was thinking about taking a bath anyway."

Undyne's single eye twitches.

"What - what is your PROBLEM? Can't you see how important this is? This would be the last soul! This is the only obstacle between us and our freedom!"

"yeah, uh, about that." You clear your equivalent of a throat. "i wanted to ask you something. namely, to leave the human alone for now."

"Huh? Wha- why?"

The fish monster lowers her voice to a somewhat-bearable level, clearly confused. Good. You finally got her attention.

"Why would I let them go? Did something happen? Did we get another human soul in the meantime?" She lets her voice out once again. "HOW DID THEY GET PAST ME?!"

"uh, no. nothing like that," you hurry to add. "it's just that they're, um, only a child. maybe you can wait until they… mature a little?"

She narrows her good eye suspiciously at you.

"I know as much as you do that you that that's nonsense. Humans are our enemies, Sans. They cannot be trusted. What if they hurt innocent monsters in the meantime?"

Tell me about it.

"i'll take care of that, don't worry."

Undyne lets out a huff, irritation straining her voice.

"You what? I'm not in the mood for your stupid jokes, Sans!"

"trust me, i wish it was a joke."

"Then what do you WANT?"

"i just said it. don't kill the human at this point."

"WHY?"

"because," you scratch your cheekbone, looking desperately for an excuse, "they might have… important information about the aboveground?"

"All the more reason for me to go after them! Let me through!"

"nah. this is a lovely spot. i like it here."

"ENOUGH!"

Surprisingly agile for someone clad in heavy armor, Undyne leaps over your head and makes a run for it. You snap your fingers and appear in front of her again.

"nope."

Impatience getting the better of her, she tries to shove you aside, but you dodge and summon a barricade of blue bones, blocking her way.

"WHAT THE -"

"i said nope."

"What are you DOING? Have you gone mad?!"

"pretty much, yeah."

"Sans, this is not funny! Stop this instant! As your captain, I command you!"

"sorry, captain, sentry sans has just found his dark and edgy rebellious side." You flash her the widest grin you could muster. "hey, do you think a gold tooth would fit me?"

"I think it'd fit you better if I knocked out a few!"

"if you want to. i'll even let you borrow them for a negligible price."

"I know you only have one HP, Sans!" she yells, making another attempt at getting past you. "Don't make me kick your bony ass!"

"then give up on killing the human."

"NEVER!"

"too bad. then looks like we're going to stand here until the end of time."

Undyne stops and closes her eye, curling her hands into fists and back, taking deep breaths to calm herself.

"Alright," she says, looking at you again. "Alright. What is this all about?"

"as i said -"

"And don't lie to me! I know you're hiding something!"

"look - you wouldn't understand. just let me -"

"Then explain it to me if you're so smart!"

You barely resist burying your face in your palms. Undyne folds her arms, her gaze fixed upon you.

"I'm waiting."

Well, you asked for it.

"ok", you shrug. "in short, the situation is the following: here in the underground we live in a perpetual time loop where on every occasion the fallen human you're currently after dies or makes it past asgore to the barrier, they can reset time itself from an artificial void existing outside of our physical world with the help of their exceptionally strong determination in order to return to one of several previously established fixed points in the timeline from where they can make another attempt to re-enact or change their previous deeds, thereby creating another, alternative timeline with every reset, all the while with us monsters having no memory of the events of the previous timelines happening at all except for a few recurring dreams and gut feelings that more often than not turn out to be result of old memories resurfacing."

Dead silence follows. Undyne is blinking at you, mouth agape for a fraction, rendered speechless by your monologue. She glances aside, then back at you, and you can practically see the gears turning in her head, trying to make sense of it all - or trying to decide whether your sanity has finally snapped.

"not that it'd matter, of course, since you'll forget all of what i just said when it inevitably resets again."

She finally finds her voice.

"What are you TALKING about, Sans?!"

"i'm talking about how our every attempt to break free from this place is in vain since the human child can bring us right back to square one whenever they want to."

"And we don't remember it because -"

All of a sudden, she falls silent, her eye widening.

"Wait. Wait a minute."

You're staring at him with an odd mixture of wariness and curiosity. You should leave to warn the kid, but you realize you don't want to do it just yet.

What is she going to do now?

"I... do remember," Undyne mumbles slowly, her voice uncharacteristically soft. "I do remember."

What are you going to do now, heroine?

"Sometimes, I have these... dreams," the fish monster goes on, looking past you. "Dreams about a human child with a smile and… red eyes." She turns back to you, frowning. "In my dreams, I fight them… and… and I die."

And then the penny finally, finally drops.

"Those were... those were memories? All those times the human killed everyone, Monster Kid, Aaron, Papyrus… and - and me… They really happened?"

You look her squarely in the eye, your voice dead serious for a change.

"yes. yes, they did."

You wait. Wait for her to say something, anything.

What are you going to do now that you know?

Tell me.

Tell me what I should have done.

"Then… then why?"

"huh?"

You spring back as she finally snaps out of her daze and shakes her head violently, her hair flapping wildly in the wind.

"WHY?!"

She bares her fangs at you, practically fuming with anger, which is no small feat for an amphibian monster.

"Why the HELL are you on their side?! If anything, it's one more reason for us not to give up! We can't let them win, Sans! We can't! We must break free and get to the surface before they can slaughter everyone again! We must get revenge for the innocent lives they took!"

Well. Here goes our hope that she'd be so confused that she'd give up.

"uh, it's a bit more complicated than that since -"

"Ugh! Even more? What now?"

This is getting out of hand. And you definitely don't intend to let her on the role you had in things going south. You rub your temples. "look, undyne, just give up on this. trust me, it'd be easier if you just took a break and -"

"And why under the EARTH should I trust you? You've given me no reason to! You knew what was going on all along, and yet never bothered to tell any of us!"

"i told the entire truth to asgore. a few times, that is, since he -"

"So Asgore KNOWS about it?"

"not in this timel -"

"I had enough of this nonsense! What's going on, Sans?"

"i told you: it doesn't matter either way. so -"

"So you're expecting me to give up and brood all day like a pathetic loser just because YOU can't be bothered to make an effort?!"

Screw this. You have enough on your conscience as it is; enough for several lifetimes. You have no intention to get into a fight with someone with a volatile temper and an infinite amount of spears at their disposal. Your left eye lights up as you try to teleport away when a flash of green blinds you for a second, and your soul is violently yanked back, anchored in space by Undyne's magic.

"You're mistaken if you believe I'm going to let you go anywhere," she says sternly. "Not until we set this straight."

"oh, for the -"

You inhale sharply. Your patience is wearing thin.

"okay. let me ask you something, captain. did you even bother to check the human's LV?"

"I - I did," she admits somewhat reluctantly. "What about it?"

"well then. you have seen they haven't killed a single soul. does it look like to you that they're planning to go on a killing spree any time soon?"

"Who knows? They did it before! You said it yourself! They are probably just playing innocent to deceive us!"

"they aren't," you state firmly, showing much more confidence than you feel. "they promised me not to."

"They made a promise to YOU of all people? Why did you even try to -"

"because it's the easiest way to prevent the killing spree you just mentioned!" You grit your teeth, maddened by this inane waste of time. "get it through your thick skull already, undyne. they won't kill anyone in this timeline."

"How do you KNOW?!"

"how i know is none of your business, pal," you growl. "and now, if you would be so kind…"

Your pupils vanish once again, making the fish monster flinch involuntarily.

"...let me go."

"No," she shakes her head, gathering herself. "You must -"

Before you could catch yourself, your eye flashes blue, and a huge draconic skull appears above you, aimed at Undyne. She cries out, a spear appearing near beside her, ready for action. If anything, that just angers you even more.

"Let me go or I -"

Or you?

Or you what?

The words die in your throat. Undyne is standing under the blaster, motionless, the spear frozen in mid-air. She's staring at the weapon almost in a trance, her mouth wide open, forming words but producing no sound. You wave your hand to dismiss the blaster, but it's too late.

Stupid.

Stupid, stupid, stupid, you goddamn idiot -

Slowly, unbearably slowly, she turns back to you. Then, only then does she finally find her voice.

"You."

You're gazing up at her robust figure, transfixed, your soul pounding in your chest, your limbs numb.

Did you really think no-one would figure it out eventually?

Serves you right, murderer.

Undyne takes a step back, her eyes wide with confusion and disbelief. Her grasp on your soul weakens a little, but not enough for you to move. You desperately want to look away, you want to look away from her face, but you can't, you must see this, you must see her reaction, this is better than any prank you ever made, better than revealing the truth to Flowey.

Heh.

Heh heh.

You were looking forward to this, weren't you?

Taking away her hopes. Taking away her dreams.

Trashbag.

"It was... you, wasn't it?" Her voice drops to a whisper. "You… you fought me."

Her lower lip trembles for a second, her breathing getting quicker.

"And I lost."

You don't want to look away.

You're fascinated.

"You killed me."

Maybe now she'll give you what you deserve.

"You killed me. And the others. It was you."

You let out a gasp as Undyne squeezes your soul, hard. She steps closer, her face hardened into a mask, her previous fury giving way to icy tranquility. She summons a spear and points it straight at your chest.

"Lay down your attacks, Sans. You are under arrest in the name of King Asgore."

Still unable to move, you shrug, trying to keep up the calm facade. If you can't beat them, annoy them.

The best prank you've ever done.

You sink your hands into your pockets, flashing Undyne a broad, affectless grin.

"you serious? you're accusing me now? based on some bad dream you had after eating one bag of chisps too many?"

"Yes. Those were memories, you said it yourself."

"i thought it was obvious, but just in case: i didn't mean the ones where impossibly absurd stuff happens."

Undyne takes a step forward, the tip of the spear coming dangerously close to your sternum. Your soul quivers a little, remembering the fights, trying to re-live the memories.

"I'm not sure anymore if it's impossible, Sans."

Your grin is getting strained. You have to stop this before it has a chance to turn really ugly.

"stop kidding, undyne. even if you can picture me going on a killing spree, do you honestly think i could do it? me of all people? who's next on the naughty list, papyrus?"

A shadow of a doubt emerges on her face, but she presses her lips together in defiance.

"Even if you didn't hurt anyone, I have enough reason to have a thorough talk with you."

"you mean interrogation."

"Call it whatever you want. Just stop resisting and come with me."

"i'd rather not, thanks."

"Then I'll make you," she declares, her voice cold and even. "Prepare yourself."

Before you can say anything else, she swishes her spear, and in the next moment, you're engaged in battle.

Well.

She wanted it.

Give it to her. Give her everything you have.

You grit your teeth and try to focus on staying calm.

"wait, no shield? no fair."

"You deserve no such thing. If you can, you may defend yourself. But I strongly recommend that you just let me capture you right away."

"ok."

Blue magic springs up from your left eye, dragging the fish monster to the ground. She cries out and falls on her knees with a loud clang, her movements restrained by the enhanced gravity. She lets out a grunt from the effort, but she struggles to her feet surprisingly quickly, another spear immediately springing up to her hand. Aiming carefully, she throws it at your arm, clearly trying to avoid causing you a whole point of damage. You dodge, moving as far as you can with your soul tied in place.

Good luck with that, meat shield.

You fight silently; Undyne is concentrating on being careful with her attacks, and you're not in the mood for chatter anymore. You try to shove her away or push her into the lake with the largest bone you can create, but she's far too strong for such a maneuver. Besides, you aren't in any better shape yourself. Blue, red, yellow spears are raining from the air all around you, slamming into the planks, leaving cracks in the cavern walls, splashing water everywhere, and damn you're feeling the lack of those extra levels now. Even knowing her rhapsodic attack patterns, it's hard to dodge in several different directions in a row. You're so used to give in to your rage, unleashing your full power on your opponents, that restraining yourself takes more out of you than the attacks themselves. But you must be careful. You're not supposed to kill her; not now. So you dodge and dodge and dodge, jumping left, right, forward, backward until you feel the room spinning around you. Your breathing is getting fast and heavy, drops of sweat forming on your forehead as you feel exhaustion creeping up on you. You can't keep up for much longer.

Wheezing from the effort, you summon a wall of bones in your next turn, blocking the spears coming from the front. You don't want to do this, but there's no other way.

Is there?

Just this once. Just for self-defense.

You slam your fist down, throwing a sharp bone toward her.

There's no other way.

The projectile goes right through Undyne's shoulder. She cries out in pain and her magic peters out, her grip on your soul wavering. You feel the restrains around the core of your very being loosen, and with a desperate effort, you finally struggle free. Your soul immediately returns to white. You must leave. You must leave right now and never look back.

You quickly dismiss the bone attacks so you can gather enough magic to teleport away. You need only a moment, only one moment to do it any other time. But you're more exhausted than you thought, and as you see her leaping up and sprinting toward you, you immediately know that you weren't fast enough. You miscalculated.

You…

...you lost.

Time slows down as Undyne throws herself at you before you could dodge, her gauntlet speeding toward your face the last thing you see before a deafening thud rings through your skull, and everything goes black.