Thirty minutes passed and the Mystery Shack came into view. There were no more government agents, and every vehicle was gone. Nobody was there. They ran into the shack, and locked the doors. They stood there for a while, catching their breath. Finally, Dipper took a deep breath, and looked at Stanley.

"Okay Grunkle Stan, we are back at the Mystery Shack," Dipper said, folding his arms. "Now, explain to us what happened to you guys thirty years ago."

Stanley sighed and looked at Stanford and Sandra for their decision. They both nodded, and Stanley turned back to Dipper.

"Listen, kids, Soos, sit," Stanley ordered, and they did.

Stanley took a deep breath, and told the whole story. Dipper, Mabel, and Soos's jaws dropped and their eyes widened. Stanley finally finished, and no one said anything.

"S-So you know Bill?" Dipper finally managed to ask.

Stanley's face darkened. "I will never forget that laugh."

Stanford and Sandra nodded in agreement.

"How do you know Bill, Dipper?" Sandra asked, looking at her nephew.

"Let's just say that we have crossed paths," Dipper replied.

"You were right, Stanley," Stanford said, turning to his brother. "We were chasing Bill's shadow."

Stanley nodded, and brought his attention back to the others. Dipper was staring at Stanford, while Soos and Mabel were talking to Sandra. Stanley sighed. Bill was somehow in this dimension, so his great niece and great nephew were in trouble.

"Mabel, Dipper," Stanley said. "I need to talk to you."

He led them into the living room where he sat them down in the arm chair. He faced them, and nervously wrung his hands.

"Kids, since Bill is back, Gravity Falls has become too dangerous for you two," Stanley said. "Tomorrow, I'm sending you back to your parents."

"Grunkle Stan, no!" Mabel shouted, jumping out of the arm chair.

"Yeah!" Dipper shouted, following his sister's lead. "We have been battling all kinds of monsters during the summer! We even fought Bill! Twice!"

"Look kids, I-"

"Father, let them stay."

Sandra walked into the room, and smile tugging at her lips.

"What? Why?" Stanley asked.

Sandra walked over to Mabel, and pulled at her cheek a little.

"They can help us," Sandra said, standing up and looking at her father.

"What? No way!" Stanley said, crossing his arms.

"Come on Stanley!" Stanford said, walking into the room. "If they battled Bill twice already, then they could help us."

"Thank you Grunkle Stanford!" Dipper and Mabel cried out, and hugged him.

A knock at the door was soon heard, followed by Soos yelling, "I'll get it!"

"Probably a customer," Stanley said, leading the others out of the room and into the gift shop.

Soos was chatting with a man who was looking around the gift shop, curiosity showing in his face. He looked like a very important man. His hair was straight and blonde. He wore a black suit and black shoes. Black sunglasses with golden rims covered his eyes, and he was leaning on a black cane. When he noticed that the others had arrived, he walked over to Stanley, and grasped his hand in a handshake.

"Mr. Mystery, I presume?" he asked in a deep voice.

"Uh...yes," Stanley replied, confused.

"My name is William," the man said, releasing Stanley's hand. "It's very nice to meet you. I just moved here from California, and I heard that this was a very interesting place. Unlike that Tent of Telepathy place."

This brought a grin to Stanley's face. He placed an arm around William's shoulders, and began to show him around the Mystery Shack. Soos followed them, sweeping furiously.

"Well, what are we supposed to do now?" Stanford asked.

Mabel squealed, and, taking Sandra's hand, she ran out the front door, dragging her aunt with her. Dipper and Stanford followed them.

***

"Oh! Oh! And over there is the library where we found out about the eighth and a half president of the United States!" Mabel said with joy as she dragged her aunt and grunkle along the road.

"Eighth and a half?" Sandra asked.

"Long story," Dipper said.

"This town sure has changed in thirty years," Stanford said, looking around the town.

"Oh, I have a question, Grunkle Stanford," Dipper said.

"Yes, what is it?" Stanford asked.

"Where were you and Aunt Sandra when Bill threw you into the portal?"

"The Nightmare Realm."

"'The Nightmare Realm'?"

"Yes. Sandra was only six at the time, so I spent twelve years taking care of her, until she was eighteen. We took matters into our own hands, and for eighteen years, we chased Bill throughout the Nightmare Realm. Then, a day came where a portal suddenly appeared in front of us. Without thinking, we leapt through, not knowing where it would go. Luckily for us, it brought us back home. Unfortunately, Bill also came through, as told by Stanley. We need you guys's help to get rid of him once and for all."

Dipper nodded silently, and their attention turned to Mabel and Sandra, who had stopped. Pacifica Northwest was facing them, and right behind her was her father, Preston Northwest. Dipper frowned at Preston.

"Well, look who it is, the riff-raff," Preston said, sneering.

"Ugh, it's you," Mabel said, rolling her eyes. "Don't talk to us. Come on, Grunkle Stanford and Aunt Sandra."

"Ah, Stanford Pines, the caretaker of these two awful children," Preston said, looking at Stanford.

"Um, do I know you?" Stanford asked.

Preston frowned. "Forgetful old man."

He turned to see Pacifica scooting slowly away from him. He took out a bell, and rang it. Pacifica looked down, and slowly walked over to her father. Dipper's hands clenched into fists as Preston put the bell away.

"Come daughter, we must leave before their simple-mindness rubs off on us," Preston said, walking away.

"Who was that?" Sandra asked.

"Preston and Pacifica Northwest," Mabel said through clenched teeth. "Just because they are rich, they think that they own everything."

"I always hated people like that," Stanford said. "We should get back to the shack. Stanley might wonder where we are."

They headed back to the shack, unsuspecting the figure following them.