“Okay, let's do this then.” Sarah said. Sans’s eyes turned dark, then suddenly his left eye flared with a blue flame. The space around them melted away as they were sent to another area. They appeared back in Snowdin, and Sarah fell forward because of the momentum. “Where are we?” She asked, flipping over onto her back.

“it doesn't matter where we are, just follow me quickly.” Sans headed straight towards his old lab behind his house.

They went inside. “Okay then,” Sarah said. “Please explain to me what’s going on, and what you guys keep talking about with resets, timelines, and different outcomes? I'm so confused.”

“ok, listen kid, all jokes aside. frisk is in real danger. if it is truly chara who is trying to possess her, then we are going to have a really big problem. you may think that you know your sister, but a lot of things have changed. sorry that this is a lot, but i really didn't want to say this in front of frisk. for her safety.”

“That still doesn't answer my question.”

“your sister has the power to reset. the power to make it like monsters never made it back up to the surface. she has the power to destroy us all, or set us free. this makes many different timelines and outcomes. here.” Sans gives Sarah his journal. “this journal contains the outcomes of all the timelines that i’ve been apart of.”

Sarah flipped through the pages, seeing multiple timelines he had made, starting and stopping, then everything ended. Then new ones started, and the pattern repeated. “Does everyone remember these things happening?” She asked.

“if it's just a regular reset, then the other monsters sometimes remember some of the events that happened. though if it's a true reset, then nobody remembers anything…. except me.”

“Why do you remember then? Is there something different about you?”

“you don't need to know why, just know that i do.”

“One more thing.” Sarah said. “Flowey took us to see some guy. His name was Gaster, I think? Do you know who he is?”

Sans’s eyes turned dark with surprise. “what did flowey say about gaster?”

“He said he was the predecessor to Dr. Alphys, whoever that is, and that he could help us stop Chara.” Sarah said, suddenly frightened. Sans turned around to face the weird machine covered by a white sheet.

“while that is true, it's not the whole story.”

“Will you tell it to me then? I want to save my sister. This seems to be the only way.”

“gaster was appointed by king asgore to study the nature of souls and to create an energy system for the whole underground. gaster was the one who built the core and the determination extractor, but gaster did most of his experiments in secret.”

“And this helps me save Frisk how, exactly?”

“the dt extractor could also be used to monitor human souls. if chara is truly taking over frisk, then we would be able to see it. then we would extract just enough determination to weaken her soul and pull chara out.”

“Weaken Frisk’s soul?” Sarah exclaimed, shocked that Sans would say something like that.

“frisk has a very powerful soul, and chara feeds off her determination. this means that if we weaken frisk’s soul, then we weaken chara too. it's the only way.”

“How do you know all of this?”

“gaster did a lot of experimentation on himself. one of them was to make another monster soul with a part of himself. he cut a hole in his left hand, and then he made me. i was weak at first, but he fed me dt pills to strengthen me. he did many horrific experiments to me, and later he created another, after i had escaped. papyrus…. he was stronger and had more hp than me. but that didn't stop gaster from doing experiments on papyrus as well. but unlike me papyrus always believed there was good in everyone.”