It was a cloudy day in Gravity Falls. Dipper was watching TV when he got up to get some food. He walked into the kitchen and started looking for some cookies. He found the jar, took it and left.
He ate and ate and ate until there was only one more cookie left. He picked it up, but he saw that there was something under the cookie. It was a wrinkly and torn folded piece of paper. He unfolded it and read:
Dear Reader,
It's been a whole year since I came to this mysterious city by the name of Gravity Falls. I uncovered all of the mysteries in this town, or at least I thought I did…
The rest had faded and was unable to read. Dipper wondered what all of this meant. He kept on reading this letter all over to try to find out what it means.
He asked Gruncle Stan what this stuff meant. He said "How am I supposed to know what this malarkey means?" Dipper left and showed Mabel.
She read it, then licked it, then ate some of it and then said "Yup. This is an old piece of paper." Dipper said "Mabel, please stop wasting my time. I need to find out what this means, and who wrote it." He left the room and set off.
He went around the town, asking people what this meant. Everyone either said "No" or "Stop wasting my time little girl!"
Dipper went to the library to try to find out what this means. Then he flipped the paper over, and found something. It read "VDMCX HR Z VDQDVNKE". Then below it said "If you can decode this, it will reveal Gravity Falls' biggest secret. If only I knew the code…" This made Dipper more interested into this letter.
He kept on reading and reading and reading, but he just couldn't decode it. Now Dipper started to lose hope. He said to himself "Maybe this isn't a real letter. Maybe it was just Mabel or Gruncle Stan was just trying to prank him.
Then he opened one more book, and in it was that exact same letter, and next to it said "Decoding the message. Dipper was excited.