Season 1 Episode 1:Day at the Mystery Shack

Well, me and Mabel, my sister came to Gravity Falls to visit our great uncle Stan, or Grunkle, for short. Everything was going great, except for when we feel something 'Fishy' is going on. And I didn't prove myself wrong, when I found this 'Journal 3' on one of the trees in the forest. The author of the journal is still unknown! But I know, somehow I can find out who's the author of this journal.
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A gravity falls inspired story by @Orange_Foxes