In the third season of "The Librarians," the world faces a new threat, this time in the form of Apep (Amin El Gamal), the Egyptian god of chaos. Accidentally released from imprisonment, Apep takes over the people who come along his path and uses these people to wreak havoc. The Librarians scramble to stop Apep, even as DOSA agents led by Cynthia Rockwell (Vanessa Williams) attempt to thwart their every move. Especially obsessed with defeating Apep is Flynn Carsen (Noah Wyle), who convinces Charlene (Jane Curtin) to reemerge from retirement and help with the cause. Rebecca Romijin and John Larroquette return as Guardians Eve Baird and Jenkins. Joining her are Christian Kane, John Harlan Kim, and Lindy Booth as the Librarians Jacob Stone, Ezekiel Jones, and Cassandra Cillian respectively. This season's guest stars include Sean Astin as Kirby Goulding, Felicia Day as Charlotte, and Efren Reyes Jr. as the Monkey King.