Sally and her twin Ben have been looking forward to their school trip to Notley Castle for ages. There are dungeons, and weapons, and a cannon to fire...But on the day, Ben is ill and has to stay in bed, so Sally promises to send him a text message every hour, to let him know what's going on.When Sally's messages start sounding very strange indeed, Ben decides to get out of his sick bed and ride to the rescue.An exciting, fast-moving story with a topical plot based on text messaging. At only 99p, this is the perfect introduction to the Demon Headmaster books for a whole new generation of readers.