Chapter 1: The Mystery Shack

"Dipper? Dipper? Are you still sleeping?" A little girl said, whispering into his ear as she poked his cheeks. "Wake up! Grunkle Stan said he's going to show us what it's like to run the Mystery Shack today."

The girl's mangy, brown hair brushed against his nose, waking him from sleep. Still perturbed, he swatted at her, unintentionally hitting her in the face. The girl yelped in pain, grabbed her face, and suddenly fell off the edge of the bed, landing on the hardwood floor.

"OW! What the hell Dipper? I'm your sister!" She stood up and raised her hand above his face. "I don't believe for a second you didn't do that on purpose. You better get up and apologize before I smack you!"

Why is that voice so annoying?

When he opened his eyes, he was startled to see a twelve-year-old girl standing over him. She had a chubby face, braces, and messy brown hair tied up in several bowties. She wore a purple sweater with a poorly drawn shooting star in the middle. Her scent was a combination of inexpensive perfume and the sharp tang of expo markers; it was so potent that it caused his nostrils to flare with every breath.

Mabel Pines.

He glanced across the repulsive room and saw the awkwardly disproportionate body of a twelve-year-old boy staring back at him. He lifted the tuft of hair covering his forehead and found the birthmark that gave him his name: The Big Dipper.

Dipper Pines.

Shooting Star and Pine Tree.

Why is this happening to me?

"Dipper?" Mabel asked, somewhat concerned, as she dropped her hand to her side. "Are you okay? I, uh, I'm sorry if I woke you up too early. I didn't sleep all night because I was so excited. It's still kind of early if you want to go back to sleep."

He turned away from her. Just seeing her made him feel uncomfortable. He threw the blanket off his bed and swapped his nightshirt for a red shirt lying on the ground.

"Don't feel bad." He said, clearly attempting to imitate the immature voice of a twelve-year-old boy. "I was planning to wake up early. There's something I want to get done before Stan wakes up."

"Really? Can I come?!" The worried look she had disappeared as she stuffed a few candy bars into the pockets of her pants. "Are you planning a surprise for Grunkle Stan?"

"Not exactly. I still have to find it first. Might take us a couple of hours." Thankfully, Mabel didn't notice anything wrong with the way he spoke. Fully awake, he grabbed a flashlight and a couple of other items off the floor. "But don't worry." He smiled. "It'll be more than worth it."

Mable smiled back and his smile grew wider.

She has no idea.

If Mabel Pines couldn't recognize that the person standing next to her wasn't her brother, no one else could.

This body is as good as mine.

The mystery twins headed out in the break of dawn, searching for the book hidden away nearly thirty years ago. He didn't know if that book could help him get back home, but even if it couldn't, he'd still need it for what was to come. It was like Stanford said, Gravity Falls attracts all sorts of weirdness, and he needed to prepare.

Bill Cipher, I'm coming for you.

=====

"Are you sure this thing even exists? We've been searching for like an hour." Mable rolled around in the dirt out of frustration. She had gotten tired of checking the bark of every tree around the Mystery Shack. Mable was quick to trust him, but she lost her enthusiasm just as fast. If nothing changed, he'd end up searching by himself. Not that it was a bad thing. Mable frequently caused problems in the show. Who knew what would happen if Mable started screaming in the first hours of the morning? It was probably a bad idea to bring her along in the first place.

"Stop complaining. I already found it." He knew it was the right tree when he felt the distinct coldness of metal. Flipping the panel open, he found the two switches. Flicking the right one twice and the left one once, he heard something open up behind him.

"This is it Mable." He grabbed journal #3 and wiped the cobwebs and dust off the cover. Lifting it into the sky, the six-fingered hand glimmered under the first rays of the sun.

"Oh my God? Let me see!" She tried to steal the journal out of his hands but he moved it out of the way and started running back to the Mystery Shack. "Dammit Dipper! Let me see! You can't make me search for this stupid book for an hour and not tell me what's inside!"

He didn't stop or look back. After a short chase, they made it to the Mystery Shack where he locked himself in the bathroom and started reading.

"Dipper!" She banged on the door but he ignored her. Mable would have her turn later. Right now, all he wanted to see was if there was a way he could go back to his original dimension.

Opening to the first page, he started reading. "June 18th, it's hard to believe it's been six years since I began researching the strange and wonderous secrets of Gravity Falls Oregon. In all my travels, never have I observed so many curious things! Gravity Falls is indeed a geographical oddity."

"But the strangest thing about this town is the question: WHY?? Why is it that one remote location houses more paranormal, alter average, and super-usual phenomena than any other location on Earth? There must be a hidden law of nature, a "Grand Unified Theory of Weirdness," which explains how everything in Gravity Falls is connected. My benefactors trust that I will use their grant money to discover something incredible, and I believe this theory could be it."

[Magical artifact discovered. Authors: Stanford Pines, Bill Cipher.]

"Mable?" He looked up, startled by the unfamiliar voice that spoke to him. "Are you still there?"

He didn't get a response, Mable must've gotten bored and gone back to their bedroom, so who was speaking to him?

[37 spells and rituals have been discovered within this artifact. Assimilate?]

His eyes widened in shock. "This is?"

[Assimilation has started.]