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, Mabel, and Soos must travel through Grunkle Stan's mind to defeat a tricky dream demon summoned by Lil Gideon.