S4, E1: In Rome, two workers unearth a mysterious ancient map in a church and turn it over to a secret sect of the Vatican known as the Heretic Order of Shadows. Back at the Library, Jenkins is preparing the Librarians for a tethering ceremony rehearsal. Because Charlene and Judson no longer tether the Library to humanity, Flynn and Baird are going to step into their immortal shoes and dedicate themselves as its eternal protectors. The rehearsal, however, is not exactly going as planned: Flynn's late, the other Librarians aren't taking it seriously, and then an ominous tone rings out - one of the four cornerstones to the Library of Alexandria has been unearthed in Niagara Falls.