Frances, a smart girl who is starting high school a year early, finds herself in the wrong places at the wrong times after mysterious pranks start happening in her small town. An older boy named Larry, who says he is an imaginary friend, offers to help Frances after he tells her that she's being framed by the Boogeyman. Frances's younger brother, Darwin, then gets kidnapped by the Boogeyman, and she and Larry follow him into the Boogeyworld dimension, which exists under Frances's bed. She then realizes that the "Boogeyman" is actually her old imaginary friend Zoe, who turned mean when Frances stopped believing in her when she wanted to grow up. Frances restores her faith in Zoe's existence and all becomes right in the world again.