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.

When the Serpent Brotherhood wants to kill Santa, the Librarians must rescue him and help him accomplish the true, secret purpose of Christmas.

An investigation into a missing person uncovers what appears to be an alien invasion.

Baird begins moving through alternate timelines that reveal the destinies of the librarians.

While Jenkins discovers there's something wrong with the Library since it returned from the Void, the Librarians all find themselves drawn back together after having been off on their own for months, to solve the mystery of a massive storm that has parked itself over Manhattan. They soon discover the culprit in both cases is none other than Shakespeare's Prospero.

The Librarians discover that Prospero's renewed magic is wreaking havoc with the technology of the world. He is recreating an idyllic forest utopia, whether we want one or not. In order to stop him, Flynn and Baird must travel back to 1611, while the rest of the team battles Prospero in the present. Little do they realize that they can only defeat Prospero in each time by finding a way to work together – separated by five centuries.