A/N: Surprise, you thought this update was going to take me approximately nine centuries, didn't you? To tell the truth, so did I, but my hazy update schedule aside, I'm very excited. I've been looking forward to the next few parts since the very start of this story, and we are almost upon them. There'll be drama, bloodshed, mystery, and complimentary refreshments in the lobby. It'll be great. Just you wait. The next chapter will be out any second now.

...I wonder if anyone else writes like I do, where I set a goal for when the chapter should come out, I write a little bit to start, do nothing for a month, then write the whole thing in about two nights.

I wonder if these remarks will even matter once the story's complete and anyone who reads this won't have to suffer from my update speed, but oh well. Here's your chapter.

CORE

It was done.

The two royal guards nodded to each other. They grasped the activation lever, grunting at the effort it took to move. But sure enough, the CORE came to life in a brilliant flash of neon light as soon as the switch reached the 'on' position. Around the guards, monsters that had gathered from every corner of the Underground started to cheer, a deafening wall of noise that rose inexorably as the lights came on—and stayed on.

There were vendors that had traveled from as far as Snowdin to sell food and novelty T-shirts to locals. Reporters from the Hotland Times, New Home News, and The Daily Waterfall were excitedly chattering amongst themselves, hoping for an exciting new detail to their story. Among them all, residents of the newly-christened CORE Residential Area and far-off visitors alike continued to cheer wildly. For them, the thermo-magical power plant's activation was the first good news they had heard in a long time, and it showed in all of them.

Except for a short skeleton in a blue jacket.

No one noticed him when he purchased a hot dog off one of the street vendors, or at least, no one paid him a second glance. After all, there were plenty more interesting things to be looking at, like the number of impromptu parades, dance parties, and the concert that an especially bold Shyren was putting on. So it came as no surprise to the skeleton that no one saw him look around the room, sigh through his teeth, then disappear into thin air.

"you missed the party," he commented as soon as the world reappeared—metal hallways and neon lights materializing before him. It was almost identical to the atrium-like room he had just been in save for one major difference.

There were only two monsters in it.

"i get it, it's not your scene but after all that work i figured you wouldn't want to be all-" sans paused. In the distance, one could hear a faint drumroll. "a-bone."

The lab was beyond silent. It was so soundless sans could hear his thoughts.

"aw c'mon, you could at least sigh in disappointment, you know?" sans paused. "no, really, what's with the silent treatment?"

"Tachyons."

Sans blinked at the doctor's unfamiliar tone, then blinked again out of confusion. "uh, bless you?"

The doctor didn't respond, and the skeleton walked cautiously to the royal scientist's workspace, a neat collection of desks and whiteboards arranged around an office chair. The scientist in question was holding a paper in his hands at an angle sans couldn't see.

"These readings, these results," he murmured. "None of them are as they should be. Not instrumentation failure, not across so much of our equipment. What is it, then? Are we asking the wrong questions?"

"doc?" and that only barely got his attention, the doctor waving him off as if to say 'not now.' It wasn't until he grabbed several other papers and tapped at a computer while Sans waited patiently that either of them spoke again.

"Sans."

"yup. that's me."

"Our testing equipment is near-flawless. They have many faults, but the ability to take accurate readings is not one of them. And with the CORE's energy output, we now have a practical way of fueling some of our more ambitious testing devices."

"yep, nice, you're two for two."

The scientist held up the papers again before muttering to himself. "Then- no, a malfunction, perhaps our model was wrong. The-"

"doc, stop," Sans sighed. "can you just- explain, please?"

The doctor paused as if only just realizing Sans' presence. "The tachyon-detection machine is not functioning as expected," he said, as if it was the most obvious thing in the world.

Sans blinked again.

The doctor spared him a glance. "I suppose you wouldn't have gotten to that point in your lessons," he mused before straightening up. "Tachyons. Hypothetical subatomic particles, they travel faster than light and backwards in time. Existence is hard to prove or disprove, rendering them more as a mathematical curiosity rather than a real exotic particle."

Sans nodded. He understood most of that and knew it was best to hold questions until the end of the doctor's lectures. "sounds like you could get some real interesting data if you could ever find them," he offered.

"Precisely," the doctor agreed. "Given accurate-enough readings and the proper methods, some believe it may be possible to even predict future events."

He motioned at a blueprint on the table. "I have long theorized a machine capable of detecting them, using much of our recovered samples of human technology and our own magic engineering. Though I have been unable to use it until now, the CORE being the only generator capable of powering it. Had I only completed it sooner..."

"i get it, but what's the problem? if the machine is broken, you can just-"

"It's not the machine being faulty that worries me," the doctor interrupted. "It's if it's right. I will need to run more tests. Before…"

He trailed off, Sans forgotten, bundle of papers in hand as he headed for the door.

It was only when he left the room did Sans dare to look at the files and papers strewn across the desk. There were datasheets and graphs that only the doctor could make sense of, though Sans was confident he could figure them out given a few minutes. But what caught his eye was a photograph, blurry and warped, as if whatever film it had been on caught fire. He could barely make out a vaguely bipedal figure, a red glow around its head, and something else out of frame, too hard to make out.

And below that, pointing to the figure, were words inked in red, 'COMPLETE TEMPORAL COLLAPSE. CAUSE? OR EFFECT? NEED FURTHER DATA.'

Sans realized, only after he set the picture down, that he knew what had been in Dr. W.D. Gaster's voice that he had never heard before.

Fear.

The elevator doors slide open with such ease that it had to have seen either constant maintenance or little in the way of passengers.

And judging by the empty corridors and platforms that made up the road ahead, I was inclined to think it was the latter.

"Can I ask," Chara began after I took a few steps out, "why we're here?"

I ignored them in favor of looking around. It was a sheer drop off of one side, but the other path went on and split into several forks.

"I mean, you're always talking about how you don't want to waste time and you want my help to get out of here as quick as you can, but then you do this-" the kid motioned, searching for the right word, "-gallivanting around, and for no real reason. We can just skip this floor, you know? It's not-"

I sighed. They were a little endearing and kind of useful at first but by now, I was getting real sick of this kid's shit.

And apparently I was thinking that so intently that Chara noticed, scowling at me. "Oh you're one to talk, what have you even gotten out of wasting time down here?"

Tell you what, kid. When you've got a functioning corporeal body and you're not trapped as an annoying ghost, you can set the rules on adventuring. Until then, be quiet. Are we clear?

Chara glared, but didn't stop me from picking up a worn and stained apron left on the ground. Might be good for repairing my coat.

Whatever. They weren't exactly wrong, stopping here had been a bit of a waste of my time. And maybe I was being a little rude, but still, you don't ask someone to travel with them and then pester them. Depending on what kind of person you're tagging along with, that kind of shit can get you shot. Not that I would do that, or that it would even work on a ghost, but the point still stands.

Also, you never realize how annoying a child can be until you're stuck with one.

I stepped back into the elevator and hit the button for the third floor, ignoring Chara's bitchfit for the moment. I almost did a double take as the doors closed, for a second I could have sworn there was another child outside the doors, frying pan in hand.

Maybe I really am going crazy.

"I…" Alphys sighed. "I wish I had done this sooner."

Undyne tilted her head slightly in confusion, and Alphys turned scarlet. "N-not this, I meant th-that, that I told you how I felt about," Alphys waved a screwdriver around. "All this. You."

"It's fine," Undyne ground out. Alphys winced, the vocoder attached to her helmet had been a spare part for Mettaton, and while it (thankfully) didn't sound like the egotistic robot, it was also a poor mockery, at best, of Undyne's real voice.

But when someone had severe nerve damage and you had little time to fix it, sacrifices had to be made.

"W-well, still, I- there's a lot you don't know about me," Alphys tried to examine her handiwork before looking down in defeat. "Despite all the times w-we hung out, I mean. There's a lot I should have- a lot I wish I told you sooner."

Undyne was silent as Alphys switched to a wrench and began tightening the final bolts, something the royal scientist was privately grateful for. It had been one thing, she reflected, to find Undyne at her door, broken and bruised from limping and dragging herself all the way from Waterfall. It had been horrifying and nerve-wracking to fix her many injuries while she told Alphys how the human had bested her, how it mocked her and left her for dead. It had been something of a small shock to Alphys when some of the scanning equipment in her lab reported an excessive amount of determination in Undyne, far more than the average monster.

It had been even more sobering to remember what happened to monsters who had that kind of determination in their bodies for any amount of time.

And it had been heartbreaking to tell Undyne. To tell her how long she could be expected to live. To tell her, exactly, how she had learned that information, and why she sequestered herself in her lab, and just why she had developed a fear of answering the phone, the mail, anything.

Alphys didn't know when exactly the tears started, but at some point her vision had definitely gotten watery, and she had dropped the tools in her hand in favor of crying as the realization of just how much she had been been dealing with all caught up with her all at once.

Undyne had been still. Then, achingly slowly, her arms had gathered around Alphys for a hug that felt, she realized, completely genuine in its care and understanding embrace.

Alphys didn't know exactly why she kept crying, or how long she was doing it, but she knew what she was going to do when it was over and her mind cleared.

She paused at her work, looking over the plans on her computer before turning back to Undyne. It was probably a dumb question to ask, but… "This is the last one. And once I activate it, I… I don't think I'll be able to fix you, even if we make it out of this. Monster bodies just aren't built for this much DT."

And I'll never know if I could have fixed you, she thought, silently bemoaning that she would never get to study how excess determination affected a living monster. And then she felt guilty for thinking that.

"No," Undyne growled. "I didn't… come this far to… stop. Do it."

Alphys pressed the activation button.

All over Undyne's suit of armor, several indents and cuts had been made to allow for metal bars that ringed around her limbs and her spine, like a wireframe skeleton. They came to life with a soft whirr, an exoskeleton Alphys had hastily made out of spare parts. They almost made Undyne look like that future-knight from the science fiction episode of Mew Mew Kissy Cutie…

But more importantly, Alphys reflected, it was able to interface directly with Undyne's mind, translating electrochemical thought into muscle movement. Thank goodness she had a few USB cables and another phone lying around to make the mind-machine interface.

Undyne rose to her feet, slowly, then faster as her movements steadied.

"W-well uh, how does it feel?" Alphys asked. Undyne didn't answer, flexing her arm and making a fist. "T-the power cells won't last long, but it'll be enough for what we need to do. Does anything feel off though-"

"Thank you, Alphys," Undyne said at last, voice synthesized and halting, but not from fear. "I know it sounds selfish but thank you. For giving me this," she motioned to the powered exoskeleton that wrapped around her armor. "For giving me a chance to save all monsterkind."

"For being my friend."

Alphys' vision got blurry, and it took her a second to register the tears before she hugged Undyne again. After a moment, Undyne returned the embrace.

Way better than the knight from Mew Mew

"Okay," Alphys breathed out when they let each other go. "Okay."

Less than an hour ago, answering the door felt too daunting for her to stomach, much less risking her life against a human. But somehow, even knowing the danger and what was at stake, with the decision made and Undyne at her side she felt…

Lighter, almost. Calm.

"Let's do this."

ENTRY NUMBER [REDACTED]: ...All data points to a catastrophic event in the near future, one I predict will be severe enough to cause a complete shutdown, if not total destruction of the CORE. Something is going to happen, an anomaly capable of immense and widespread destruction. Will have to investigate further...

"Ma'am, with all due respect, we need to get you out of here, now. This area is unsafe."

"All the more reason for me to stay then! I can't very well leave without the rest of my brood! Or would you have me abandon them to- to whatever danger it is you insist is lurking about?"

"Ah, of course not, ma'am, just, how long do you think it'll take to gather up the rest of your… family?"

"Hm… hard to say, I know Regina split off with her own clan somewhere near the CORE, but it shouldn't take too long to gather everyone. There's only a few thousand of us, after all."

"A few-!" the dog-like monster grabbed his head, looking like he'd rather be anywhere else, doing anything else.

I felt about the same.

I turned to Chara, who was also observing the whole thing.

What was it you said? The way ahead is clear, stop wasting time, let's just go? Because I'll be honest, this—I motioned towards the crowd of guards at the stairs in front of some kind of hotel—is not my idea of 'clear'.

Chara glared, storm clouds of smoke rolling off their face and flickering intermittently like sheet lightning. "I just said that to keep you moving, you know, since we weren't accomplishing a lot with you wandering around on the lower floors."

And that worked out great, I thought while looking for a way past the guards. There were the two guards from earlier, those bipedal dogs with black cloaks and battleaxes. But with them were even more guard dogs, one with a huge set of medieval armor, another sniffing curiously at the rocky terrain, and one more having an intense debate with a spider-lady about the morality of leaving spiders behind in a dangerous area.

Just my luck they were all crowded around the only set of stairs that led to the exit.

"Oh for-" Chara sighed. "Just kill them all or something, I doubt they'd slow you down."

I frowned. It's not the worst plan, but I can't help from looking over at the kid, annoyed.

It's about the principle of the thing. I don't actually want to kill them, you know. That's why I was trying to consider a different route.

"You keep saying that! And yet you always end up killing whatever's in front of you anyway," Chara shot back. "Or did you just forget about Toriel and Undyne?"

That was different and you fucking know it. They were actively trying to stop me from getting out of here, these guys don't even know I'm here yet. I don't make a habit of killing people outside of self-defense.

"Mhm, tell that to Silus."

That's-

I froze. So did Chara.

"Where did you hear that name?" I asked, slowly.

"I-" Chara looked ready to fight or bolt. "You don't-"

"TELL ME!" I roared. How dare you. How fucking dare you, you insolent little shit, like you know a goddam thing about why I-

"Hey, what was that?"

"Over here!"

Fuck!

I stepped back, knife already unsheathed and in my hand while I got ready to meet the guards. And judging by the skitter skitter sound of too many feet hitting the ground, I was probably going to end up fighting the spider-lady too.

Joy.

I threw a quick glance backward. When this is over, we're going to have a talk, you-

Then I did a double take. Chara was gone.

Burgerpants—who had long given up on having his name changed—cleaned the counter for the eighteenth time in his shift, which wasn't even halfway done. "If you've got time to lean, well darling, you've got time to clean!" Mettaton always admonished.

God he hated his job. And his boss. And… most facets of his life.

At best, he was overworked and constantly, constantly the outlet of some random person's frustration that he hadn't gotten their fries in time, or that the glamburger didn't look exactly as it did in Mettaton's show. Over time, he had learned to numb himself to those types of monsters, and thought he was fairly proficient at putting on a fake smile for the day, retrieving pre-made food from behind the counter and tallying it up on the register. It was a chore all the same, but one he could deal with.

But on days like today, where no one was coming in, and Burgerpants was left with nothing but his thoughts and his stupid name for company, he truly felt his job was at its worst. Often- hah, no. Always, whenever that happened, he'd just end up mindlessly cleaning the shop and keeping an eye on the door and the clock, wishing someone would show up, or that his shift would end soon. Anything to distract him from having to clean and constantly think of how he had gotten to this point. Even Mettaton showed up on occasion to berate him for not doing his job as 'fabulously' as he could be doing it.

But not today. The lobby of the MTT Resort was as silent as a tomb, and all the more unnerving and annoying as a result. There was a point at which daydreaming turned to internal philosophical debate about whether or not he was sleepwalking himself through life at the ripe old age of 19 and oh my god he hated his job.

Because of that, he was cautiously optimistic at the sound of a scuffle from somewhere outside. Maybe, if he was lucky, someone who wasn't a complete jerk would come inside and make light conversation for a few minutes. Then he could replay the conversation in his head for a little while.

He could dream, at least.

It was a full forty-three seconds after the sounds outside died down that someone walked through the door. Burgerpants started; he hadn't even heard footsteps.

"Welcome to the MTT-Brand Burger Emporium, home of the Glamburger™," he greeted automatically, as he had done literally thousands of times before. The customer only paid him a little attention during the whole spiel, which was fine, it meant Burgerpants was free to observe the new arrival. Tall, with a heavy coat and glowing red eyes. Probably a bit strung-out judging by how sluggishly he approached, as if life itself was weighing him down.

He could sympathize.

"Can I take your order?" he asked once it was clear the guy wasn't going to say anything.

Those red eyes turned to him, as if finally registering his presence. Burgerpants wondered if maybe it wasn't such a great thing that someone had come in today.

"Why are you here?" he asked.

Ho boy. One of those customers.

"Bad life decisions," Burgerpants answered.

"No, I meant with the evacu- nevermind. I'll have a-" the guy paused. "A… glamburger?"

"Alrighty! Here you go, have a FAB-U-FUL day," he said, reaching next to the register with practiced ease and passing one of the pre-wrapped burgers while the guy paid up. Once that was done he just… stared at it. Eyes fixated on the counter, not moving.

Why did I have to get one of the weird ones today?

"Can I get you anything else, valued customer?"

"Do you ever feel like you've made a mistake?"

He blinked at the non-sequitur. "I work at a fast food joint, buddy."

"Not a little mistake, either," the guy mumbled, probably more to himself than to Burgerpants. "I mean something where you really, genuinely messed up?"

"Pft. Who hasn't?" he tried to joke, then stopped when the guy kept staring blankly ahead.

Burgerpants sighed.

"Listen, guy, I don't know what your deal is. And I don't think wandering into a burger joint and asking for life advice is your best bet-"

The guy looked up.

"-But I'm pretty sure that we all make mistakes, and the best we can do is try and learn from them, move on. And I know that ain't always easy, or possible-" god he knew way too much about THAT. "But it's important that we try, y'know?"

"...Yeah. I know," the guy said after a while. Then, "Thanks."

"Don't sweat it, people have breakdowns in here, five, ten times a week."

"Mhm. Thanks for the burger," the guy said as he walked out. Burgerpants glanced down, the glamburger he'd sold was still on the counter.

He watched the doors close, then breathed a sigh of relief when the guy didn't immediately get back inside.

"What a weirdo," he mumbled, reaching into his pocket for a joint.

ENTRY NUMBER [REDACTED]: Preliminary experiments have failed. All models point to an end my actions have only hastened, and now I have no choice but to welcome it. I will do what I must.

Please forgive me.

The first thing I noticed about the CORE were the lights.

It was a maze of neon lights on metal floors, like Hotland's upscale cousin. Circuitry and lights ran across the walls, throwing up a wave of iridescent blue and purple light on everything. Steel hallways and catwalks that hung over clouds that had to be ozone, judging by the smell. And everywhere, side-paths and intersections decorated with industrial equipment and side rooms. I couldn't tell if the whole place was a power plant or a residential area. Maybe both.

But the second thing I noticed was… how quiet it was.

All the puzzles in the area were deactivated, the lasers down and not even doors barred to stop me. It wasn't hard to stay on the main road either; signs cordoned off every detour with notices of "Full evacuation now in effect." and "Remain calm." A few screens were mounted to walls, notices scrolling down of monsters asking if anyone had seen their loved ones, but the only person around to read them was me. All that was really left was the steady thrumming of idle electronics in a very big, very empty room.

If I was feeling more introspective, I'd say walking through the place would have left me with more time to contemplate my actions, where I'm going in life, and how to find Chara.

But for the moment, I just couldn't bring myself to care about that. What concerned me far more than their temper tantrum was how they knew about-

"U-um, you! Stop right there!"

...You gotta be fucking kidding me.

"You may have come this far, but your reign of terror ends now, human! You've walked right into our trap!"

Dr. Alphys was shouting into a megaphone at me, with something that looked very much like a laser pistol in her other hand. But more concerning was the monster right next to her.

Undyne, bruised, beaten, and born again. Now sporting a suit of armor that seemed bigger and more wicked than before, ringed with reinforcing struts that reminded me of the gutted exoskeleton frame in power armor. Eyes were still alive though, still filled with hate.

I knew I should have shot her while she was on the ground.

"A-all of the Underground is counting on us!" Alphys said, maybe to hype herself up. "We can't lose now, so take your best shot, human, we-"

"Fuck this," I muttered.

Faster than either of them could react, before Alphys even finished her speech, I drew my gun and shot her with every round in the chamber.

Alphys scarcely had time to react when the first bullet hit her.

It was hard to tell how the human would fight. It was fast, she knew that well enough from Undyne, but it was hard to say what kind of tricks the human would have up its sleeve. Still, Alphys was confident that the personal shield generator she fashioned out of spare parts would do the job.

And it almost did.

The first round stopped an inch in front of her, repelled by a shimmering barrier. The scientist flinched, then took a step back with the second impact, then the third-

And on the fourth hit, the shield collapsed. A spiderweb of electricity coruscated into the air in front of her as the barrier was taxed to its limit, and there was nothing to stop the fifth shot from tearing into her.

Alphys fell to the ground. Dimly, she was aware of someone shouting, of a face looking above her, tears falling down a vaguely-fishy face. Undyne.

She took a ragged breath. It's fine, she wanted to say, feeling very calm. It's fine as long as you're up, as long as you-

Something rolled down Undyne's cheek, and Alphys started to realize just how much of Undyne's face was streaked with tears and how much was her.

How much of your determination came from me?

The last thing Alphys ever saw was Undyne's face, melting as her determination surpassed the limits of her broken body.

Then Alphys died.

You can find out a lot about someone when they're dying.

There are the common ones; a thrill of fear flashing across the eyes of a stone-cold killer. A peaceful man erupting into psychotic rage as his last vestiges of life fade away. You grow used to seeing them after the first six or seventeen, but there were a few that gave me pause, once. This old criminal, some thief with a bounty on his head. He knew I was coming for him, and instead of running or fighting when I found him, he sat down, told me to do what I had to, and awaited my judgement. An NCR soldier stationed near Camp Searchlight, severe case of radiation poisoning. Face all blotchy and half sloughed-off, those guys were so under-supplied they didn't even have painkillers to spare. And the first thing she asked when she saw me—between bouts of vomiting her insides out—was to end her suffering. To just make it all stop.

There's a lot to learn about someone when they meet their end, and if you see it enough they tend to blur together. But the ones where you learn something about yourself? You never forget those.

Not ever.

I had torn the limbs off of fiends and fed them to starving coyotes. I bombarded an entire Legion town with kiloton-yield nuclear missiles because I could. I did things no one in their right fucking mind would ever forgive me for, no matter how evil or guilty the targets were. None of it really bothered me all that much.

But this was the first time I made someone melt from sheer despair until they were nothing but dust, and something about seeing it reminded me of those times. When Private first class Andrea Lane begged me to put her out of her misery, the way her skin slide off her face after the gunshot in a kssschlop sound.

It all came rushing back from watching the anguish in Undyne's face as she fell to her knees, completely ignoring me in favor of kneeling over Alphys' dust and whispering I'm sorry, I'm so sorry and Alphys, Alphys, please...

Undyne fell to the ground, most of her lower half already liquified. She continued to apologize until she could do it no more, leaving only a metallic skeleton.

Some part of me thought that if Chara was here, the kid would be laughing their ass off. The other part of me plodded onward, through the door and into the next corridor, leaving the dust and the corpses behind. Footsteps were automatic, like walking in a dream. I kept walking until all I knew was that there was an elevator in front of me, and that I'd give anything to not turn back.

I hit the 'up' button and waited for the doors to close before I slumped against the wall. Not out of exhaustion, that's not the right word for why it felt so hard to stay upright. I was…

I was just so tired.

The elevator whirred to life and left the CORE behind.

ENTRY NUMBER ?:

I HAVE SEEN IT NOW

THIS SWIFT AND TERRIBLE END OF MINE

UNYIELDING, INEVITABLE, AND…

HOW VERY CURIOUS

UNENDING

WE'LL JUST HAVE TO SEE ABOUT THAT

LET'S SAY HELLO

A/N: Well, that's it then. We're almost done. Next chapter coming soon.

See you there.