Lord Hugh Anthony Disward, also known as Huey, had recently lost his grandfather, Sir Wesley Disward, a renowned collector of rare books six months ago. In his grandfather's testament, Huey was declared the heir of his manor and all the property within it. However, to inherit the legacy, he had to take up the guardianship of the Bibliotheca Mystica de Dantalian - an archive of forbidden knowledge - and look after a mysterious girl named Dalian. As Huey settles into his grandfather's abode, an old rival drops in for a visit, someone whom Wesley's murderer killed. Dalian, who tags along with him, discovers that this murderer possesses a Phantom Book - a cursed tome that Huey's granddad tried to seal away. As the book puts their lives in danger, Huey unravels a startling revelation - the Bibliotheca Mystica de Dantalian and Dalian are one entity. Dalian reveals the key to unlocking the knowledge within her, which Huey accepts, and together they manage to seal the Phantom Book away. Thus, begins an unlikely partnership, and Dalian and Huey solve mysteries surrounding other Phantom Books.