When a prehistoric beast snatches Mabel's beloved pig Waddles, the Pines family must journey to a land trapped in time to rescue him.

After 'Lil Gideon swindles the Mystery Shack away from Stan, everything in Gravity Falls appears to be even more west of weird - Dipper, Mabel and Grunkle Stan are forced to move in with Soos and his grandmother, while the town remains enamored with Gideon's charm. Meanwhile, Grunkle Stan isn't certain he can take care of the twins and is considering sending them back home. With their summer in Gravity Falls threatening to come to an end, Mabel and Dipper decide to take on Gideon and win back their home.