For 13-year-old goth girl Cassie (Emily Osment), fitting into a new school and neighborhood isn't easy, but she entertains herself by playing pranks on the 'popular' kids and her little brother, Max (Alex Winzenread). As Halloween approaches, Cassie's search for scares leads her to a mysterious Halloween store and an unusual book called The Evil Thing. When Max begs her to read the book to him, Cassie finally gives in, ignoring the warning 'Do Not Read Aloud.' It's when they get to the last page of the book and its clear warning about the Evil Thing - 'Don't Think About It' - that the spooky adventure really begins. Priscilla (Brittany Curran), the most popular girl in school, and Cassie's arch-enemy, is kidnapped along with Max, and Cassie has no other choice but to search for them.