Twin brother and sister Dipper and Mabel Pines are in for an unexpected adventure when they spend the summer helping their great uncle Stan run a tourist trap in the mysterious town of Gravity Falls, Oregon.
Dipper and Mabel go trick-or-treating in the summer and encounter a candy-loving monster who threatens to devour them if they don't bring him sweet things to eat.
Stan leaves Mabel in charge of the Mystery Shack while he is gone and the power goes to her head.
While Stan, Dipper, Mabel and Soos are falling in a bottomless pit, they tell stories to pass the time.
When Mabel befriends a cute merman trapped in the public pool, she's determined to help him out. Meanwhile, Dipper decides to volunteer as a lifeguard to see Wendy.
The twins discover a hidden room inside the Mystery Shack and compete over who should have it.
When Mabel discovers that her favorite boy band is actually a bunch of imprisoned clones, she sets them free, only to decide on keeping them for herself. Meanwhile, Dipper is convinced that Robbie plans to brainwash Wendy with a secret message hidden inside one of his songs.