Thomas and Julia are enjoying their fall vacation in the Forbidden Forest, at the home of their great-aunt Magda, the good witch. There, the brother and sister try to keep a promise to their grandmother by staying away from danger and magic. But all their best intentions fly out the window when they learn that someone has moved into Count Crudelis' castle. Who is this person, and how can they hide from Magda's crystal ball and magic cards? What happens during the night when the blood moon is in the sky? Thomas and Julia must face someone extremely dangerous who is planning something terrifying. Something that will lead to the doom of the Forbidden Forest. They must do everything they can to prevent this from happening.