The Librarians return to TNT tonight with a fourth season of madcap fantasy adventures. The series was spun off from the hugely successful Librarian movies, which starred Noah Wyle as Flynn Carson heading up a team of librarians whose job it is to track down artifacts that could pose a threat to humanity if they wind up in the wrong hands.

The first three seasons had a pretty strong arc running through the various adventures. The first season had a somewhat Arthurian theme to it, which is a theme that the series has retained somewhat due to Jenkins (John Larroquette) being Sir Galahad whereas the original caretaker of the Library Judson (Bob Newhart) was Merlin. To that end, every season to date has used classic literature and mythology as source material.

This fourth season promises to be a little different. Much has changed for the Librarians since the show first aired. For one, Cassandra Cillian (Lindy Booth) no longer has a tumor in her brain so now has full use of her gifts as a genius mathematician and then some.

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Added to the that, the Librarians have become more of a team than when they started. Sure, we still get the odd bit of bickering between the different characters, but it is more like a dysfunctional family now than it is a group of people learning to trust each other.

So what lies in store for Flynn Carson, Eve Baird, Jake Stone, Cassandra Cillian and Ezekiel Jones this season?

Thus far TNT has been fairly tight-lipped about the series, but the little we do know is that the series is going to take on a number of different tropes. The first two episodes see the team face off against Santa Claus’s brother, the Patron Saint of Thieves. Other episodes included run-ins with Civil War ghosts, a Freaky Friday-style body swap scenario and a shady casino that’s obviously using an artifact to steal the luck of its gamblers.

The greatest challenge to the Librarians this season will come from the Library itself. With Charlene no longer tethered to the Library, which kept it grounded in humanity, a Guardian and Librarian must step forward and take on the mantle. As Jenkins officiates the tethering ceremony, which bonds their pair to the Library and gives them immortality, it looks like Flynn and Baird are set to commit, but then a woman from Flynn’s past reveals herself to be one of the Library’s dirty little secrets.

The most notable thing about Season 4 of The Librarians is the return of Rachel Nichols as resurrected guardian Nicole Noone. This character was played by Sonia Welger in the original Librarians: Quest for the Spear movie from 2004.

No-one will fill the vacancy left open by the departure of Charlene (Jane Curtain), who uncoupled herself from the Library’s magical hold in last season’s final episode. By the way, Charlene was Guinevere and the original guardian, with Eve (Rebecca Romijn) being the Library’s current guardian.

We can expect a bit of friction between Eve and Nicole Noone. Adding to that friction will be the fact that Flynn, who is currently romantically involved with Eve, had a relationship of sorts with Noone. At least that is how it appeared in the movie, which saw the two ride off for further adventures on her motorcycle.

Rachel Nichols, who plays the resurrected Nicole Noone, has a great mix of genre credits to her name. Over the course of her career, Nichols has appeared in G.I. Joe: The Rise Of Cobra, Conan The Barbarian, the 2009 Star Trek reboot and much more. She is best known to television viewers for the time-travel series Continuum, which ran for four very successful seasons.

Another fan-friendly addition to the cast of guest stars is John Noble who will play Vatican Bishop Monsignor Vega. Noble will bring gravitas to the series and will hopefully get a few scenes playing off against the brilliant John Larroquette.

Noble of course is known for his roles in TV shows such as Fringe, Sleepy Hollow and Elementary and film fans will know him for his turn as the madness-afflicted steward of Gondor, Lord Denethor, in 2003’s multi-Oscar-winning The Lord of the Rings: Return of the King.

The Librarians airs later tonight with a double bill of episodes on TNT at 8pm ET/PT.