Twin brother and sister Dipper and Mabel Pines are sent to spend the summer with their "Grunkle" Stan in the mysterious town of Gravity Falls, Oregon. Upon their arrival, they sense there is something strange about the town and together they begin to unlock its secrets.

Dipper, Mabel, Soos, and Wendy attempt to discover the identity of the author of the journals, while Stan continues to work on operating the mysterious portal beneath the Mystery Shack. Together, the group must stop Bill Cipher, a dream demon who wants to take over the world.