Hetty’s unexpected resignation and the arrival of Claire Forlani's character shook up NCIS: Los Angeles Tuesday, and it appears this surprising arc has just begun.

Next week's season finale features a visit from NCIS star Rocky Carroll as Director Vance, and will include a reveal that leaves viewers - and Callen - reeling.

Intrigued yet? NCIS: LA creator and show-runner Shane Brennan spoke to TV Line about the root of Hetty’s actions and a whole lot more. Excerpts below ...

On Hetty's mission: There is nothing in this series that is not connected to Callen. While it’s kind of a buddy show, everything ultimately goes back to Callen."

"We are on Callen’s journey. And the shift, the twist, the reveal at the end of this season – that Hetty is involved in something – ultimately plays back to Callen."

"This has been laid out for sometime, and it plays out next season. In fact, what we reveal in the last episode is another big step in Callen’s journey. It’s something that the audience will go 'Wow!' about. They’ll be as surprised as Callen is."

On the back story of Claire Forlani's character, Lauren Hunter: "I’ll give you a line from the finale. Hunter tells Callen she knows Hetty better than Callen does. So to say there’s a relationship between Hunter and Hetty is an understatement."

"In her first scene with Callen, in the final episode, I put both of them through the wringer. Basically it’s a confrontation, but it’s a confrontation in five different languages. It becomes a confrontation and a contest at the same time."

"There are questions, Callen wants answers – and Hunter has some of those answers. And the other interesting reveal is that Vance makes his presence known in L.A."

On Cristine Rose's guest starring role in the finale: "It’s probably one of the most powerful reveals. When we introduce her in that episode, the hair on the back of your neck is going to stand up ... She is just a fabulous, fabulous actress."

On the new partnerships of Season 2: "It was important to really establish the team. Eric Christian Olsen, from the moment I saw him, I knew he was perfect for the show. This year was about Deeks joining the team and solidifying his place in it."

"And of course we did the same, much more low key, with Nell Jones (Renée Felice Smith). To me [NCIS: LA] is about partnerships. I was keen to get Deeks and Kensi (Daniela Ruah) together as partners, with the kind of rapport that happens with Sam and Callen - and likewise, though I didn’t anticipate it, with Nell and Eric (Barrett Foa) as well."

On Deeks and Kensi's "thing": "We’ll just have to wait and see. We revealed some interesting backstory on Deeks this season, and there’s more to find out there, but next season we’ll focus on Kensi – the why and where of Kensi."

"Again, it goes back to partners: When you reveal something about one character the other doesn’t know, it puts pressure on the partnership. It makes them ask questions."

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.