Someone is killing off potential Librarians and it's up to Flynn Carsen and his new Guardian, Colonel Eve Baird, to save the three that are left.

The Serpent Brotherhood is trying to return magic to our world. Flynn, Colonel Baird, and the potential Librarians must stop them before it's too late.

The Librarians' two-front battle comes to a head when the Library is simultaneously infiltrated by DOSA and Apep. Flynn, Baird, Stone, Cassandra, Ezekiel and Jenkins must all put aside their differences in an attempt to save the Library, the world and themselves.