After his grandfather's death, Lord Hugh Anthony Disward inherits his manor on the condition that he becomes the guardian of the forbidden library, the Bibliotheca Mystica de Dantalian, and cares for a mysterious girl named Dalian. When an old rival reveals himself as the murderer of his grandfather, Dalian and Huey uncover the dangerous Phantom Book in his possession. As they face peril, Huey learns that Dalian and the library are interconnected, and together they confront the threat of the cursed tome. Thus begins an unexpected alliance as they tackle enigmas spawned by other malevolent Phantom Books.