Marsha Thomason

On Tuesday's episode of White Collar, the team takes on an extortion case against adoptive parents. To nab the bad guy, Diana (Marsha Thomason) and Clinton (Sharif Atkins) must go undercover as a couple trying to adopt a child.

Going undercover is Thomason's favorite part of the gig.

"The parts on the show I really enjoy are going undercover, which we do quite a bit. That's really fun because then Diana gets to become an actress," Thomason tells TVGuide.com.

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"I just like when Diana goes undercover, because she becomes somebody else. She's always in these outfits that couldn't be less Diana, which is really fun. But she isn't uncomfortable with that, she embraces it because she's a professional and will do anything to get the job done."

Diana's undercover missions have also given her colleagues and viewers new insights into her back story. Earlier this season, fans learned about her years of traveling as the daughter of a diplomat and about Charlie, her bodyguard and father figure who died protecting her.

Looking ahead, Thomason says Diana's current living situation will get the spotlight as the curtain is pulled back on her girlfriend, Christie.

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"[Diana]'s very, very ambitious. Whatever it takes to get the job done, she'll do," Thomason says. "She does her best to juggle both. It's intimated that Christie isn't happy about coming back to New York, so I imagine there will be some bumps in the road. "

However, whatever troubles lie ahead, domestic or otherwise, she says Diana can handle it.

"Diana's kind of known as a bit of a no-nonsense ball-breaker; which I really like. I like that sometimes Neal approaches her with caution at times because he knows she doesn't take any s---," Thomason says. "She's not to be messed with."

Thomason promises that Diana's relationship with Neal (Matt Bomer) will develop in a "very slippery" manner over the next few episodes. As for the mystery surrounding the music box, she's tight-lipped about any such progress.

"Eventually they'll be a crescendo, but it's very slow," Thomason says.

White Collar airs Tuesdays at 9/8c on USA.