Dipper and Mabel Pines go on summer vacation to Gravity Falls.

The uncle Stand’s house is the mystery shack, there go many tourists to see the strange things that he invents.

Mabel wants a boyfriend because she feels away from her parents.

Stand tells Dipper to go put some signs to the forest that indicate the location of the shack.

The tree where Dipper puts the sign, has a strange sound.

Dipper finds a door in the tree and there is a machine, moves a lever and opens a hideout and in the discover a very old book.

NORMAN

At that time Mabel arrives and surprises Dippper, go to the hut and teaches the diary but she doesn't attention because her new boyfriend arrives.

Dipper suspects Mabel's boyfriend because he looks strange, he thinks he's a zombie, so he decides to investigate it.