17 year old Dipper and Mabel Pines have come back to Gravity Falls for summer. But in her Dreamscape, Mabel is being hunted by Shadows of the Underworld. The only one who can help her is the long thought dead Bill Cipher, yet his help comes with a price. Now, they are on a journey to stop the Shadows, and on the way, Mabel's star inside her might shine through the darkness in Bill.