Humongous Studios makes the weirdest horror movies ever, and in its next film, the monster is a real-life threat!  Sean and Holly’s dad owns the wackiest business in Grover’s Mill: a horror filmmaking studio. For his newest movie, their dad has decided to feature a gigantic robot octopus as the star of the show. When Holly and Sean visit the studio with their friends, they are excited to get a first-hand look at how movies are made. Unfortunately, there is one problem: Gigantopus is completely out of control, and its alien master plans to use the star to take Grover’s Mill back to her home planet! In a fight fit for the big screen, Holly and Sean must battle Gigantopus and save their town from being sucked into space. This may turn out to be their dad’s oddest movie yet!