On a mission to retrieve a WMD, NATO counter-terrorism expert Colonel Eve Baird crosses paths with occult expert Flynn Carsen, who's on his own hunt for a lost demonic artifact. After a furious battle of gunfire and magic, Baird finds herself drawn to the mysterious man who claims to be simply "a Librarian". Baird is soon invited to join the ancient organization known only as "the Library", based in an endless Library of artifacts hidden deep underneath New York City. Now teamed with Flynn - who's half-mad from a decade of world-spanning magical adventures - Baird finds herself embroiled in the ancient battle between the Library and the Serpent Society. The Society are occultists who wish to bring magic back and use it to rule the world, led by the mysterious Dulaque. Soon Flynn and Baird are in a race against time to save the lives of other extraordinary people the Serpent Society has targeted for assassination: synesthete science genius Cassandra Cillian, rough-living art and history expert Jacob Stone, and infamous high-tech thief Ezekiel Jones. These three reveal a deeper conspiracy, a plan by the Serpent Society to hunt down the key to controlling all magic - the ancient Crown of Camelot's King Arthur.

The Librarians have retrieved King Arthur's Crown - only to discover it's part of a deadly trap laid by their ancient enemies, the Serpent Society. Now the Library is lost in space and time, Flynn is mortally wounded, and Dulaque has recovered the real key to his scheme: Excalibur, King Arthur's magic sword. On the run, the Librarians retreat to a small safe house, an Annex to the Library, run by the brilliant and cranky Jenkins. The Librarians must stop Dulaque from bringing magic back to the world - but they have to break into Buckingham Palace to do it.

With Flynn on the road searching for a way to recover the lost Library, Baird now has to keep three neophyte Librarians - Cassandra, Stone, and Ezekiel - alive, all while training them to investigate bizarre mysteries. Their first case, a simple missing persons investigation, leads them to a wildly successful modern agribusiness in Boston. They discover, however, that the "modern" business has been around a very long time, and its success is based on sacrifices made by the firm's employees. Literal sacrifices.

The Serpent Society makes a bold move to kill one of the world's most powerful magic beings and steal his energies for their own crusade - Santa Claus! Luckily, one of Santa's oldest friends, Jenkins, catches wind of the kidnapping and sends the Librarians on a rescue mission. Santa, it turns out, does more than deliver gifts; he collects all the good will from people around the world during the year, and then returns it to us on Christmas Eve. If he's stopped, humanity will fall into despair and ruin. The Librarians rescue Santa, but are pursued around the world by the Serpent Society. Colonel Eve Baird, Christmas grouch, finds herself smuggling Santa to the North Pole before Christmas Eve counts down. From stolen cars to bar fights to crippled cargo jets, the Librarians are in a race against the clock to save Christmas. But even the Librarians are unaware of the true, secret meaning of Christmas, the one Santa does not share with even his closest friends.

When the entire planet is rattled by earthquakes, Flynn Carsen returns to reveal the secret truth behind the disasters: the Dragons are waking up. The Western and Eastern Dragons are preparing for war and they'll be looking to the Library - the only universally acknowledged neutral party in the secret world of magic - to negotiate a truce. Unfortunately not only the Dragons show up, but representatives of every secret power in the magical world, demanding satisfaction. Even worse, Flynn is maneuvered out of his position to negotiate. Ezekiel Jones, selfish thief, and the one person who loathes him most - Jenkins - must bring peace to the magical world. Flynn and the others set off to find the stolen object at the heart of the conflict. As they search the Vatican for clues, Baird and Flynn clash over leadership styles. Flynn finds that he can't step back into being the boss when Baird's been leading the team and building trust with her people. Things only get worse when they find the artifact, which twists each team member into the worst version of themselves. Can Baird stop the evil version of Flynn Carsen from bending the powers of the Library to evil?

What do a car crash caused by a "giant", a disappearing college student and a naked Mayor have in common? The Librarians investigate an outbreak of weird incidents in a small town and discover that someone somehow is bringing Fairy Tales to life. The Librarians wind up on the trail of the Libris Fabula, an ancient book that brings any story written within it to life. Their search grows complicated as more of the townsfolk fall into the roles of the classic fairy tales, and grows deadly when Jenkins reveals the Libris feeds on the life energy of its victims. Solving the mystery would be tough enough with a Sheriff gone Big Bad Wolf and a Wall of Thorns suddenly surrounding the town, but when the Librarians themselves start playing the parts of the classic Fairy Tales, there seems to be no hope at all of saving the townspeople or themselves. Luckily, one Librarian finds himself as the classic Fairy Tale trickster.