When a dragon is murdered at a top-secret dragon-Fae peace conference in Vienna that the Library is mediating, the fate of worlds lies in the balance. Tasked with solving the case, Vale and Irene immediately go to 1890s Paris. It seems that the murder victim had uncovered possible proof of treachery by one or more Librarians. But to ensure the peace of the conference, some Librarians are already hostages in the dragon and Fae courts. To save the captives, including her parents, Irene must get to the bottom of this murder. But was it dragon, Fae, or even a Librarian who committed the crime? -- adapted from back cover