Twins Dipper and Mabel Pines visit their eccentric great-uncle for a summer in Gravity Falls, Oregon, where he operates the world's most bizarre museum. As soon as the twins arrive in Gravity Falls, they discover something amiss in the remote town.

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.

Stan throws a big weekend party to promote the Mystery Shack. Dipper makes clones of himself to impress Wendy. Mabel fights for the Party Queen title in honor of her two friends.