An FBI arc that kicked off with this season’s premiere comes to an intense climax in Tuesday night’s finale — and in doing so, it puts Special Agent Tiffany Wallace (played by Katherine Renee Kane) in quite a moral predicament.

Season 6 opened with FBI agent Trevor Hobbs (Roshawn Franklin) being killed while working undercover with Tiffany, a death for which Agent Wallace felt some blame. That tragedy was revisited six weeks ago, when Tiffany grew convinced that the terrorist who killed Hobbs — Hakim Siran (returning guest star Antwayn Hopper) — was back in the States.

Agent Hobbs and Special Agent Tiffany Wallace in the Season 6 premiere
Tiffany’s repeated defiance of orders in that April 9 episode, based on her unfounded suspicion that Hakim has sneaked back into the U.S., drew scrutiny from Isobel, only for the JOC to learn in the closing moments that Tiffany was right. Hakim is back.

In this Tuesday’s finale, “Ring of Fire” (airing at 8/7c on CBS), the Somalian terrorist group behind Hobbs’ resurfaces, sending the team on a chase to take the baddies down for good.

“It’s a very, very turbulent, shocking” finale for Tiffany, Kane tells TVLine. Hakim’s return “is something she obviously has been is in great anticipation of, and it’s going to be a closing-out of a very heavy chapter for her.”

Reflecting on this arc in which Hakim has evolved into almost Tiffany’s elusive “Joker” has “been a whirlwind,” the actress observes. “There were times when it really threw her for a loop, and we saw where she was almost unraveling, but it’s nice to see her be able to gain some self-possession and go at her nemesis with a bit of gumption, but also a lot of self-control.”

Well, she will exhibit at least some self control, since this week’s episode will once again test Tiffany’s ability to color inside the lines when the insidious Hakim is in her sights.

Last time around, “We were really worried about Tiffany” as she defied orders to pursue her own agenda, says Kane. Now, in a season finale that ratchets up the intensity, “It shocked me a bit when I first read it, to see how much it was bending her out of shape,” Kane previews. “She’s done a lot of work on herself between then and now, and change doesn’t come overnight, but I think we’ll absolutely see her approaching this case and her work with her team with a lot more grace, a little bit more wisdom.”

What will FBI viewers — and fans of the Tiffany character, in particular — be feeling as Tuesday’s finale draws to a real nail-biter of a final act?

“I would say that it’s going to be exhilarating,” Kane promises. “It brings up a lot of questions and a lot of static at some points, and I think people could be along for a really thrilling ride.”