In this season of The Librarians, our heroes embark on new, action-packed adventures, risking their lives once again to save the world. They face off against Santa's brother the Patron Saint of Thieves, try to save a town plagued by ghosts from the Civil War, battle a casino that steals luck, endure a body switching fiasco and join forces with a time traveling Librarian from the past. But their greatest challenge will come from within the Library itself. With Charlene no longer tethered to the Library, which keeps it grounded to humanity, one Librarian and one Guardian must step up and take the mantle. As Jenkins organizes the Tethering Ceremony, the high ritual that will bond the pair to the Library forever, thus granting them immortality, Flynn and Baird seem poised to make this sacrifice. Until a woman from Flynn's past reveals herself to be one of the Library's dirty little secrets.