Sans' death changed the small family. Without his biggest supporter, his biggest fan, Papyrus backed into his shell. He still talked, but he rarely shouted. He still played, but never vied for the lead roll in anything. Puns just about made him break down in tears. His smiles weren't as big.

Gaster, on the other hand, became much, much louder. When Papyrus was around, he was fiercely protective, always at his son's side, ready to defend him in an instant. Never did he hesitate to sweep up his son in a hug, or hold tightly to his hand. And when Papyrus wasn't there, he became something akin to the man he was before he created Sans. The tall, imposing Royal Scientist who completely disregarded any rules other than his own (and even those, sometimes), driven by a dark anger towards his enemies. Any who got in his way were quickly brushed aside, and any who attempted to help struggled to keep up.

At Gaster's command, all efforts were set towards building traps. He was determined to have his test subject. All his time not spent with Papyrus was put toward this.

Papyrus wore Sans' jacket. He wore it always, the too-long sleeves rolled up on his arms, hands lost in the folds of the pockets. When things got bad, he could pull the hood over his face and curl up in the jacket, almost able to pretend that Sans was there, hugging him.

Of course, in the long run, that only made him feel worse.

Gaster and Papyrus spent all the time they could together. As soon as Papyrus got home from school, once he started going to school again, that is, Gaster would leave the lab and head home, no matter what was going on. He would help Papyrus with his homework, and then the pair would find something to do together.

Papyrus had a hard time with that. One of the best parts of doing just about anything was being able to tell Sans about it. Sans' smile had always widened when Papyrus showed him something, anything, really. He had always loved to see everything Papyrus had to offer him.

And now he didn't. Couldn't.

Another thing was Frisk. The human. They lived with Queen Toriel, and went to school with Papyrus. Once the initial shock of "yes, I am a human," wore off, they were pretty much a normal kid. They were reasonably nice to everyone, and everyone was reasonably nice to them. Frisk and Papyrus were alright friends.

They didn't talk much. On Papyrus's first day back at school after Sans died, they didn't say a word to him. Just walked up and wrapped their arms around him and patted his back. Since then, they stayed pretty close to him, and he took willingly to their company.

Not a replacement for Sans; that would never happen. No, Frisk was not someone to fill the aching void in Papyrus's Soul, but instead to soften the jagged edges of Sans' absence. They did not help Papyrus forget, indeed, much of what they did, in a peculiar way, reminded Papyrus of his late brother. But they helped him to remember not with sorrow, and instead with a sort of quiet contentedness, to let Papyrus look back on his memories of Sans without the agony.

And slowly, slowly, the two members of the Gaster family settled into their life without their third counterpart.

~o0o~

The Royal Scientist was irritated. Anyone could see that, had they been allowed on the tenth floor of the lab. As it was, only Gaster's four assistants were there to witness his fury. He paced the hallways, gesturing wildly and roaring angrily, Speaking, or, rather, Shouting in Hands.

Because he had finally come up with a workable trap to catch one of the Corrupt, and Asgore wouldn't let him go out to set it up.

Asgore would let a group of soldiers go set it up, but not his Royal Scientist.

But of course, Gaster couldn't allow that. He was the only one who knew how to set it up, firstly, and then he wouldn't be surprised if it got broken or uncalibrated in transport. On top of that, a large group of monsters in hostile territory wouldn't go unnoticed as easily as the few it would take to set it up, and the whole point of a trap was for it to go unnoticed, until it was too late, at least.

So no, Gaster would not allow his trap to be set up by soldiers.

Eventually, he decided that there was nothing else to be done. He would go set it up himself. Regardless of the king's orders.

He told Papyrus only that he would be leaving for a few days.

Papyrus wanted to come with him, but there was not a chance that that would be allowed. He was not going to let Papyrus on the warfront. Not ever. He was not going to run the risk of losing the only family he had left.

"You'll be staying with Queen Toriel," he told Papyrus two days before he left, "and the human. It'll be fun, you'll see. You won't even notice I'm gone, and then I'll be back."

Papyrus was curled up in his lap. This was the most comfortable sitting arrangement for both of them, despite the couch being more than wide enough for them to sit side by side. "But Dad," Papyrus whimpered, holding tightly to Gaster's sweater, "I- I wanna stay with you. I don't want you to go anywhere. I don't want anything to happen." There were tears in his eyesockets.

Looking at his son's face, Gaster almost decided then and there to risk letting the soldiers set up the trap. But he hardened his resolve. He was setting up the trap to protect Papyrus, after all. With a living test subject, he would be able to find a cure to the Corruption, and end the War.

Before Papyrus could be hurt any more.

Gaster used the sleeve of his sweater to wipe Papyrus's face dry. "Papyrus, it'll be alright. I'll be safe. Nothing is going to happen to me." He clutched Papyrus closely to his chest, letting Papyrus's skull rest on his shoulder. "I'll be fine; I'll come home perfectly safe."

"If it's so safe, why can't I come with you?"

Crap. He's smart. I mean, it obviously runs in the family, but... Gaster sighed. "Because..." He scrambled for an excuse. "...it's- ...it's not safe for small skeletons. I'll be fine, because I'm grown up, but you're still small, so you might get hurt." Gaster screamed at himself internally. AAAAGGH. That's... That's not even a real excuse! Idiot. I'm so stupid.

Papyrus seemed to accept it, though. He let out a defeated sigh. "... Someday, I'm going to grow up tall. And then I'll be able to go everywhere, and do anything, and nothing will be able to hurt me, because I'll be grown up, and then... I'll stop everyone from hurting anyone else."

Once again, Gaster's Soul almost shattered. Papyrus sounded so... Dejected. Broken. So sad. Gaster blew out a breath and gave Papyrus a squeeze. "Yeah." He quietly agreed. "Someday..."

~o0o~

Two days later, with Papyrus safely under Toriel's care, Gaster stepped off the boat and onto the ground of Waterfall. He had a large, heavy backpack, and the two of his assistants that had come along had similar loads. Soon, the trio was walking into, and then through the Pure army camp. They drew some curious looks, but all could see the Royal Scientist's dark expression, and no one dared get in his way.

No one on a rank lower than he, that is.

"Hey!" Commander Undyne stepped in front of him, her one eye glinting furiously. "I don't know if you heard or not, but this is a warzone! You can't just go walking out there!"

Gaster paused for a minute. "Commander, I realize this is a warzone, and if it were not a warzone, then my being here would be pointless."

"And what exactly is the point of your being here?"

"That is classified information on a need-to-know basis. Of everyone in this camp, my assistants and I are the only people who need to know."

For a moment they stood, Undyne's hard glare met by Gaster's equally cold, calm one.

The Commander folded her arms across her chest. "You're not going out there. It's too dangerous."

Gaster sighed and massaged the ridge of his nose. "Commander, this is a war. Everywhere is dangerous."

"Yeah, but out there, it's more dangerous."

"Well, then. I suppose I shall just have to be quick." He started to walk around Undyne, who grabbed his shoulder.

"No. You are not going out there!"

Again, they were locked in a staring contest.

"Doctor," Undyne began, "I realize you are still in mourning. We all are. But that's no reason to be rash, or go get yourself killed! What would happen to Papyrus? The Commander-- he-- wouldn't want his brother to be alone."

For a moment, it seemed like Gaster might explode. How dare she use my own sons to stop me from fighting. He closed his eyes for a moment and took a few deep breaths. Had Undyne been any less of the brave soldier she was, she would have withered under the glare he gave her when he looked at her.

As it was, she managed to flinch only slightly.

"Commander Undyne," Gaster growled through clenched teeth, "you will get out of my way now. I will not waste any more time here. I will go do what I intend to, regardless of your opinion. If you must do something, then you can accompany me to ensure I am safe, if it becomes too dangerous. Otherwise, I bid you farewell." He shrugged out of her grip and stalked onwards, gesturing for his assistants to follow.

Undyne stared after him, stunned at the fury in his voice. After a moment, she trailed after him, fuming. If the Royal Scientist was killed on the battlefield because Undyne had neglected to send someone to keep him safe...

...Especially because that would be the second member of the Gaster family she failed to protect...

Better not to think about that.

As they walked, she saw Greater Dog nearby. After gesturing him over, she told him she was going with the Royal Scientist, and to keep watch of things 'til she got back.

Then she was jogging to catch up with Gaster, whose long strides had already propelled him to the border of the camp.

It was not without trepidation that Undyne found herself following him deep, deeper, and yet deeper into hostile territory. The farther they got, the less of Waterfall's ambient light there was; the water had lost its glow, the crystals all emitted a dark, almost anti-light, and the echo flowers were wilted.

On top of that, there was a general unfriendly, Corrupt atmosphere.

Undyne shivered and kept her Magic at the ready. "I really don't think we should be here." She whispered.

Gaster glanced over his shoulder at her. He still looked calm, but there was a sort of tension in his eyes that unnerved Undyne.

"Yes. I think here will be far enough." He set down his backpack and gestured to his assistants, who did the same and began unpacking.

"What is all this, anyway?"

She didn't really expect an answer, not when she had been so bluntly denied one before. Maybe it was the uneasy atmosphere that made Gaster feel the need to trust her, or maybe he hadn't wanted to say anything in front of the others at the camp. Either way, he answered. "Trap." Undyne had to strain to hear the murmur of the Royal Scientist's voice. "Catch one. Study it. Find a cure."

"...Oh."

With that, Gaster left her to keep watch, and began assisting his assistants in assembling the trap.

It was probably much more complicated, but from what Undyne could tell, it looked like it was a set of steel panels, laid into the ground. When a monster, preferably a Corrupt one, stepped on the pressure plate at the center, the panels folded upwards, trapping the monster in a box.

Yeah. It had to be more complicated than that. The Corrupt would never fall for that, and on the off chance that one did fall for it, a metal box wouldn't hold them in.

Admittedly, by the time the scientists were done, Undyne couldn't see the trap at all. Had she not seen them setting it up, she wouldn't have known it was there at all.

"Alright," she quietly hissed, nervousness making her scales itch, "now let's get outta here."

Gaster nodded. "Agreed. Better that we're not here when they come."

They set off, as quickly and quietly as the could, heading for safer territory.

They got back to the camp without incident. The daylight simulating crystals were dimming into twilight, so Gaster stayed the night there. He set off for home first thing in the morning, and arrived by ferry in Hotland later that afternoon, and made it to Toriel's house in New Home by fiveish.

He had barely knocked on the door once before it was flung open and Papyrus, small as he was, tackled Gaster to the ground in a hug.

Dazed from the fall as well as the sheer speed of things, it took Gaster a minute to realize that the weight on his chest was Papyrus, and the nearly bone-cracking pressure around his ribs was Papyrus's arms.

Once he did figure it out, he wrapped his arms around Papyrus, returning the hug. And for a minute, he just lay on the ground, happily cradling his son in his arms.

~o0o~

A/N
Welp, I'm still writing these chapters a heck of a lot faster than I had anticipated. And I'm also getting my homework done... A lot slower than I normally do. But hey, as long as it's done by the due date, it doesn't matter when exactly I do it, right?

Anyway, thanks for reading, and votes and comments are not only always welcome, but always appreciated, too!