Five years after the defeat of Bill Cipher, Mabel and Dipper Pines prepares their 18th birthday party. But when Robbie Valentino and his friends break into Ford's inventory of anomalies, a dark force from the past awakens.

Five years after the defeat of Bill Cipher, Mabel and Dipper Pines prepares their 18th birthday party. But when Robbie Valentino and his friends break into Ford's inventory of anomalies, a dark force from the past awakens.