Demon and the Princess (Mabel x Bill)

The journal

After they woke up from a dreamless sleep. They got ready and ate breakfast. Mabel made some Mabel juice for the whole family! Well, Dipper knew what was going to happen when he drink it, so he avoided it.

After finishing their breakfast, their uncle decided that they should put up sign to attract more customers to the Mystery Shack. They set off to the forest.

*after a few sign*
(Ting,ting)

Mabel: What was that ?
Dipper: I don't know, but this tree sound like it is made out of metal.
Mabel: Ooooo... a mystery.
Dipper opens the panel, and inside had some lever and buttons. Mabel pushed the big red button.
Dipper: Mabel! What are you doing !? You don't know what it does!

Suddenly, the ground shook a little.
Dipper: WHAT WAS THAT ?!
Mabel: Look! Over there!
She pointed to a rectangular hole on the ground, both of them slowly walked to it. What they saw was a journal with a golden six finger hand with a number '3' on it. Dipper picked it up, and flipped a few pages.

Dipper: Mabel look! It said 'trust no one'!
Mabel: Do you don't trust me Dipper ?
Dipper: I do but what about Grunkel Stan and the town's folks
Mabel: Dipper ! You don't even trust your own Grunkel??
Dipper: Mabel! Quiet down!
He said with a hint of angry in his tone.
Mabel: Whatever bro...
She pouted.

*after putting up the signs*

They went back to the Mystery Shack, they looked exhausted.
Grunkel Stan: Uhh... hey, you did a really good job today.
Dipper: Umm thanks ?
Mabel: No problem !
Grunkel Stan: So as a gift, you guys get to choose something from the shop.
The twins looked at each other with anticipation. Dipper had chosen a blue and white hat with a blue pine tree printed on it, as for Mabel she had chosen a grappling hook.
They both look happy.

After that, they went back to their room. Dipper was all about that journal while Mabel was adding stuff into her scrapbook. But little did they know that they were being watched.