One morning at Gravity Falls, Oregon, at the Mystery Shack, Dipper Pines was fast asleep in his bed when he felt something or someone hoping up on his bed. He opened up his tired, weary eyes and noticed his twin sister, Mabel Pines, jumping up and down on his bed with her usually glee expression.

"Wake up, dorkus!" She laughed.

Dipper glanced at the time and saw it was 6 am in the morning. He frowned, annoyed to be woken up so early. "Mabel, seriously, it's 6 am in the morning on a SATURDAY! Please stop bugging me and go back to sleep!" He groaned and laid back down, pulling his pillow over his head.

Mabel stopped jumping and just smirked. "Fine, then, sleepy head! I guess that means I'll get to see Grunkle Stan's surprise first!" She playfully stuck her tongue out at him and rushed downstairs.

Dipper rolled his eyes and tried to go back to sleep, but not one second had past when he heard his sister screaming, "AHHHHHHH! DIPPER! COME DOWN HERE! QUICK!"

Dipper sat up his eyes widening. It sounded like his sister was in a lot of trouble! He could tell by her voice. He practically leaped out of bed and rushed downstairs. "Mabel? Mabel? Are you okay? What's wrong?"

"THAT!" Mabel pointed on the ground where their Grunkle Stan's fez and one of their Grunkle Ford's guns was. "They were coming out of the kitchen when they suddenly….. VANISHED! And some of their stuff fell on the ground!"

"WHAT?!" Dipper's eyes grew even wider as he stared at the objects. He turned back to Mabel. It couldn't be true. People don't just disappear into thin air! "Mabel are you sure?"

"Yes!" Mabel wailed, her eyes on the verge of tears for her Grunkles' disappearance. "And not shortly after, a note appeared on the ground and it said they took Stan and Ford! Here it is," She handed the note to her brother.

Dipper grabbed the note from his sister and peered at it. "What? Who? Who took them and wrote this? Why would they need Stan and Ford?" He began pacing back and forth, which is what he usually did when he thought long and hard about something.

"I don't know," Mabel whipped her eyes on a piece of tissue paper. Suddenly, she looked really hopefully. "Wait…. Maybe this time this is a prank set up! I bet Justin Keprank'd took Stan and Ford and is trying to trick us into thinking they are missing and come out with them when we least expect it!"

Dipper glared at her. "Mabel, are you serious? How can you be messing around at a time like this?"

"Okay, you're right! I was just joshin a bit! Trying to lighten the mood a bit," But Dipper was right. This was VERY serious and knew in her heart that there was literally no way this could be a prank. Suddenly, she gasped as another thought came across her and looked very very worried. "Dipper…. You don't think it's….. the triangle guy…. Do you?" She gulped as she said those three words.

"What?" Dipper looked at Mabel as a worry knot feeling came when he heard what she said. "Bi-Bill?" he stammered nervously. "It... it… can't be! Why would he need Stan and Ford?"

Suddenly, the twins' good friend and the Mystery Shack's handyman, Soos entered the room in his usual happy manner. "Hey dudes!" Soos grinned at the twins, beaming at them. "What's-" Suddenly, Soos vanished into thin air!"

Mabel screamed, pointing to where Soos had stood. "Dipper, did you see that?!"

Dipper did see it. He blinked and rubbed his eyes, gaping at where Soos had stood a second before. "What is this?" He hissed, pulling out the Journal 3 from his vest and flipping through it, trying to found out what this was.

"Oh my god! Dipper look! People all over town are vanishing too!" She wailed, looking at the window, staring at the disappearing Wendy, Old Man McGucket, Gideon Gleeful, Pacifica Northwest, her best friends Candy and Grenda and other townsfolk. "Oh, even Candy and Grenda vanished! Even my best friends! Oh this is the worst! What the heck is going on here?"

Dipper grabbed his hair in a total panic after seeing that too, shutting his journal in haste. "I don't know!" He blurted out. "But we haven't disappeared yet, so if this is Bill's doing, he must want us for something!"

"Well we aren't gonna let whoever this is do this to our friends!" Mabel stated with a determined expression. "We need to stop him and get our friends back and put an end to this case!" She made her hand to a fist and held it out to Dipper. "Mystery twins?"

Dipper nodded solemnly at her words and gave her a determined grin, hitting his fist lightly against hers. "Mystery twins."

With those words said, Dipper and Mabel set out to find out who this mysterious person was that had caused their friends to vanish and to get them all back.