Sebastian's skills and reputation for troublemaking become infinitely valuable when his sixth-grade class is threatened by a supernatural menace. Monsters in human form, known as Morugs, have infiltrated the school faculty to find the Arkus, the student who has inherited the power to stop them. Sebastian and his friends must undermine their plans and find the Arkus first, all while keeping the Morugs from realizing that he knows about them. While using pranks and dangerous stunts to interfere with the Morugs' efforts, Sebastian also begins investigating his fellow students. As the Morugs escalate their efforts to find and eliminate the Arkus, Sebastian begins learning of the experiences of those around him and finds that even the most ordinary people have fascinating stories to tell. Somewhere, in one of those stories, lies the key to defeating the Morugs.