To my luck I found the trio that is my group just standing together. Cross looked disturbed while the kids looked perfectly fine. 

Fresh was hanging out above in my strings looking down at Cross in what I could only assume was a mocking way. Also he noticed me first thanks to his height advantage.

"Heya Error! Looky what I found!" He said pointing down at the three who then turned to me.

"Error!" The two kids said before running over. Cross not too far behind keeping a skeptical eye on Fresh who was just waving while his shades said 'BYE BYE'. 

"The game is over and you two won."

They both cheered at this and I gestured them back to the portal that I left open. They ran for it and Cross looked hesitant when he saw I wasn't moving.

"Go on, I need to deal with this first."

"If you're sure..." Cross hurried to catch up with the kids and I heard Fresh drop down from his spot.

"Well? Where's my thank you?"

I groaned a bit and heard Fresh chuckle as he walked around to face me.

"Come on. A thank you. I did just save your butts over there. Free of charge."

"If you're asking for a thank you then it's not really free of charge is it?"

He paused a bit before realizing I was right. 

"Ok, you're totally right. I'll admit. Though I am surprised."

"What? Why?" 

"My homeslice, you are so cold yet here you are saving some randos."

"You make it sound like I wouldn't save children."

"Nah, you got me wrong. I know you save people. I'm just saying you're a bit different from when we first met. Maybe that's a good thing."

"I don't know what you're trying to imply-"

"Then don't worry your glitchy noggin on it broski! I still want that thank you but.... I can wait. You got some radical homes waiting for you right?"

"Yeah...." I headed back to the portal still on guard about Fresh. He just doesn't make sense to me.

I picked up the pace and leaped through the portal closing it immediately behind me. No one was in the bedroom save for Cross but he was in the doorway waiting for me.

"I was starting to think you weren't going to come back."

"Well I did. Where are the others?"

"They're downstairs, come on."

We headed downstairs and saw the two kids by the couch but walked past to get to the kitchen where Sci was. He had the stuff I gave him on the table neatly together and when he saw us he looked pleased.

"Well before our unexpected visitors showed up I figured out what happened to your pal."

"Is it permanent?" Cross asked causing Sci to chuckle. 

"No, not even close. Based on what I read, the chemical residue I found and the powder it seems like he was trying to make some sort of healing concoction."

"So... what went wrong?" I asked not getting how it turn Nightmare into a child.

"My guess is a premature reaction. Happens all the time in science. Did you hear anything before finding him?"

"I remember a boom sound when I was walking by but I figured he was mad about something and threw a book against the wall. After about twenty, maybe even more, minutes I went back to ask him something but he wasn't there. Which lead to me asking two others then searching his office again and finding the kid."

"Well that boom might have been the reaction. That powder is some chemically sensitive stuff in heat. It's possible the stuff in the beaker wasn't cooled off enough and caused that whole mess."

I huffed a bit feeling a headache coming along. Nightmare can't use healing magic. None of us in his domain could do that. It makes sense as to why he would try to make some sort of healing potion. But, he should have told someone incase something happened.

"You said this wasn't permanent, how long will he be like this?"

"At most he'll be like this for the next twenty hours, at the very least maybe eight hours."

"So that would be....."

"Either tonight or the next morning in the domain we live in," Cross said after some thought.

"Thank you Cross my brain could think for a moment." I sighed and relaxed my posture. "That's a relief I guess." 

"Yeah, you guys have nothing to worry about." 

We stayed with Sci for another hour since Moon was having fun playing with Papyrus but we did eventually have to part ways. Moon being sleepy from all the playing made it easier for us as Cross wrapped him up again and we headed out. Sci held an equally tired Papyrus as he waved bye before closing the door so the heat didn't escape.

"So are we going to tell the others?"

"No, we'll just say Nightmare went out and the kid was returned. Just hide him in his room and guard the door hopefully he changes back soon." 

We headed to the Anti-Void once more just to drop off the blanket and went back to the castle. Cross hurried off to hide Moon while I went to Nightmare's office to put everything back the way it was. 

"I really hope he doesn't remember anything..... or would that be worse?" 

Once everything was done in the office I decided to check up Cross real quick and we both agreed not to say a word about what happened... unless Nightmare asked then we would figure it out. No one else had to know what Nightmare looked like when he was younger if he hasn't told anyone yet.

Turns out while I was doing my usual looking through the aus Moon turned back to Nightmare while he was asleep. I didn't know until I went down to get some breakfast. He was sitting there with a mug of coffee, I think, and nothing else. 

"Good morning Nightmare."

"Good morning." 

He seemed to be in his thoughts mostly so I kept quiet and made my way to the table. I took a seat at a chair not too far from the dark skeleton and not too close. I decided to eat one of the fruits at the table for my breakfast.

"I'm going to need you to come by later and report what you have found out so far about Underswap. Not now of course, after you eat."

"Sure, I assume you want to meet at your office?"

"Yes."

Eventually Nightmare did get up and start to head out which made me relax. 

"Oh one more thing."

"What is it Nightmare?"

He tossed something to me and I caught the object. Looking at my hand I saw the Cross puppet I entirely forgot about. I could tell my expression amused Nightmare.

"Let's not talk about the events of yesterday to anyone else." 

With that said he headed out and I rested my head on the table with a groan.