Branches On A Tree

The Man Who Speaks In Hands

Sans immediately collapsed as his feet hit his bedroom floor. He was back in Snowdin, in his own room. The sudden headache he'd gotten throbbed behind his eyes, making it difficult to think. He tried to soothe it by massaging his temporal bone, but instead of relieving the pain, it only made it worse.

As much as he hated to admit it to himself, knowing that Gaster was still out there scared him to death. He was supposed to be dead. He'd perished in the core years ago, way before the time loops even began.

At least as it turned out, whatever magic his father had used on him, it couldn't prevent him from using his shortcuts and there was no trace of him here, so at least he had that going for him. An unnerving feeling in his gut told him that Gaster wouldn't be far behind and considering what he just said about having watched all these years, he would most likely know where he and Papyrus lived and that meant they needed to leave immediately.

Papyrus still didn't know about what happened all those years ago, and Sans was determined to keep it that way. Telling him the truth now would only stir up unnecessary guilt and he didn't want that for him. He was snapped out of his thoughts when someone suddenly abruptly knocked on the door.

"SANS? I KNOW I HEARD YOU JUST NOW! WHEN DID YOU COME BACK?" Papyrus nasal voice yelled from the other side of the door. "COME OUT OF THERE! I KNOW THERE'S NOTHING LEFT IN YOUR ROOM TO PACK BECAUSE I AND UNDYNE PACKED YOUR STUFF FOR YOU! BY THE WAY, WE'RE GONNA HAVE TO BUY YOU A NEW MATTRESS ON THE SURFACE..."

Sans slammed open the door. The hasty and unpredictable movement caused Papyrus to flinch and step back in surprise.

"BROTHER! YOU SURPRISED ME. WHAT'S WRONG? DID SOMETHING HAPPEN?"

"yeah, so we need to leave. now."

"WHAT ABOUT OUR STUFF?"

"we'll get new stuff on the surface."

"WHY?" said Papyrus and raised an eyebrow in bewilderment, but he quickly followed Sans down the stairs.

"just trust me, okay?" Sans muttered. He felt skittish and for a reason, he wasn't entirely sure of, he needed to check that the coast was clear outside, though it was highly illogical that Gaster would have been able to keep up unless he too knew how to use a shortcut too. At this point, he wouldn't be surprised.

Being as distracted as he was right now, using a shortcut could be hard, and even more demanding with an extra person along. He made the best effort he could to calm himself down, by trying to regulate his rapid breathing, but it proved to be a hard task to clear his mind.
He knew he'd need to use a shortcut in order to get him and Papyrus to the surface. Frisk would still be there and he could ask them to reset straight away.
Remaining in the Underground, now that he knew his father was out there, was treacherous and he wouldn't risk it even if he knew things would reset soon. He wouldn't take any chances considering Gaster.

In his mind, he was already trying to chart all of his locations and actions in previous timelines so he could make sure to keep himself and Papyrus away from Gaster.
Sans' head kept throbbing and he suddenly started to feel very dizzy. He did his best tried to ignore it and tried to focus on planning instead. So far Gaster had never shown up in any other timeline, so tracing previous movements should be safe even if he would know about their whereabouts.

Undyne, who had been gathering stuff in the kitchen raised an eyebrow and crossed her muscular arms when she noticed them.

Adding yet another person through the shortcut just wouldn't happen and Sans wouldn't hesitate to leave her behind. Gaster had no connection to her, and even if he had seen how close she and Papyrus were and decide to try something on her, she'd be more than able to fend for herself.