(Caution: spoilers about the Season 2 premiere of NCIS: New Orleans ahead)

As Season 2 of NCIS: New Orleans opens, New Orleans is on high alert as an unknown sniper is gunning down seemingly random people in broad daylight -- in large crowds, no less. Residents are thrown into a state of panic, of course, and with Mayor Hamilton (Steven Weber), the senator and the media demanding answers, the NCIS N.O. team is desperate for a break. Making matters worse, Special Agent Meredith Brody (Zoe McLellan, who departed the show at the end of last season) has made it clear she isn't coming back.

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Just when Agents Pride (Scott Bakula), Percy (Shalita Grant) and LaSalle (Lucas Black) think they have a lead, they not only discover that they were wrong, but something worse is on the horizon: a new agent has been sent to investigate them. Enter FBI Special Agent Tammy Gregario (Vanessa Ferlito), whose no-nonsense, abrasive style causes friction with the team -- especially Agent Percy -- right away.

"I would describe her as pretty bad ass," Ferlito said in an interview with TVguide.com. Agent Gregario is a trained sharp shooter, a skill set that's hardly new for Ferlito, whose turn as Catherine "Charlie" DeMarco on Graceland meant handling firearms -- albeit not the sniper rifle Gregario handles now. She's an uptight, "stand-up girl" Ferlito said, with a tough shell who's making sure the NCIS N.O. crew is doing things by the book. But although she's there to keep them in line in the first few episodes, we'll see that she has flaws, too --including a devastating secret that eventually comes to light.

"Around Episode 5, you'll start to see a vulnerable side to her," Ferlito said. "Pride knows what it's all about." If you listen closely in the premiere, she drops a clue: This isn't her first time in New Orleans.

"Her weakness is this burden she carries from her past. It's really bad. She feels responsible that many people suffered as a result of something she was involved with," Ferlito said, hence her character's choice to join the FBI. "She doesn't trust anybody because of what happened. She's a wonderful agent but when she comes to New Orleans it opens old wounds and she has to face it and get closure. She doesn't find it anytime soon -- it's going to drag out a little bit."

We don't yet know who this person is but Ferlito offered a clue: it's "very possible" it was a lover.

Isn't it always?!

NCIS:New Orleans Season 3 premieres Tuesday, Sept. 20 at 10/9c on CBS.

(Disclaimer: TVguide.com is owned by CBS.)