Contains spoilers for this episode and earlier episodes.
Mabel's confidence at miniature golf collapses when Pacifica Northwest arrives and boasts about her own ability. The rivals arrange an after-hours match, and Dipper helps Mabel practice because he wants to see Pacifica lose. Their visit uncovers the course's secret: tiny Lilliputtians move the balls through its themed obstacles. The groups living at different holes compete fiercely over which is best. Dipper suggests promising Mabel's prize sticker to whichever group helps her win. Mabel hesitates over cheating, but agrees. When Pacifica returns, pressure from her parents makes the contest feel just as serious to her as it does to the twins.
The Lilliputtians manipulate Mabel's shots, giving her an advantage that Pacifica cannot explain. Their own rivalries soon become more dangerous than the game. One group kidnaps Pacifica and offers to kill her as a service to Mabel, while another captures her servant Sergei. Mabel refuses to reward any of them and tries to end their fighting, only to make herself their shared target. She frees Pacifica, and the girls cooperate to escape the course with Dipper. Outside, Mabel admits that she cheated and apologizes. Pacifica softens enough to take a ride with the Pines family rather than wait alone for her parents. Stan praises Mabel for rescuing her rival, and the competition ends without a winner's celebration.