 Emily Osment plays 13 year old gothic girl, Cassie, trying to fit in at her new school. To entertain herself, she plays a series of pranks on the popular kids (Brittany Curran from The Suite Life of Zack and Cody and Cody Linley from Hannah Montana) and her younger brother, Max. When she goes to a Halloween store looking for new tricks, she finds a little book called  The Evil Thing.  The Evil Thing is a monster two kids made up, and if you think about it, it will haunt you. And if you try not to think about it, you can t think of anything else! Maybe that s why the book says   Don t Think About It.  on the last page. And that s when the spooky adventure begins.