Ben is a teenage boy who, along with his twin sister Sally, are the main characters of Demon headmaster spin-off book, "Beware of the Demon Headmaster". This book is considered a spin-off as it doesn't feature any of the main SPLAT characters.
On the day of the much anticipated school field trip to Notley Castle, Ben falls ill and has to miss it. He makes Sally promise to text him every hour to tell him what is going on. The texts start out normal but suddenly change and become weird messages about someone called "the master",