Dipper and Mabel discover that their seemingly cherubic new neighbor, Lil' Gideon, happens to be the town's adored psychic. But when Lil' Gideon guilts her into dating him, she and Dipper soon learn that his cuteness can fade all too quickly.

Dipper wants to correct a mistake he made in the past with assistance from a time machine. Mabel is overjoyed when she wins a pet pig at a fair.

When Waddles is snatched by a prehistoric beast, Dipper, Mabel, Stan, Soos, and Old Man McGucket must journey to a mysterious land trapped in time to rescue him.

Li'l Gideon swindles the Mystery Shack away, forcing Grunkle Stan and the kids to move in with Soos. While Stan weighs how he can still care for his grandniece and nephew, they decide to take on Gideon.