Matt Czuchry Matt Czuchry

"Welcome back to the dark side."

With those celebratory words from his former rival, Alicia Florrick (Julianna Margulies), one chapter closed and another re-opened for Cary Agos (Matt Czuchry) on The Good Wife. After spending two years working for the State's Attorney's Office, Cary was welcomed back to Lockhart & Gardner on Season 3's penultimate episode.

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Cary may be returning to the same firm that once canned him, but he is no longer a naïve, shroom-taking lawyer fresh out of Harvard. "He has more confidence than arrogance," Czuchry tells "The experience that Cary has been through has definitely helped him gain a greater understanding, not only in his professional [life], but in his personal life. That can't help but translate into the work he's going to do and the dynamic he's going to bring into Lockhart & Gardner in Season 4."

After engaging in a junior associate competition with Alicia during Season 1, Cary was dismissed in favor of his more connected co-worker. But instead of moving to a new city or going to another private firm, Cary went to bat for the firm's biggest opposition — and one of Alicia's greatest enemies: State's Attorney Glenn Childs (Titus Welliver). "It was supposed to be six episodes," Czuchry says. "[Cary] basically was able to show a window into that other side, which they enjoyed.  That's why the writers kept it going for so long."

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What started out as a brief arc turned into Cary working for both Alicia's enemy as well as her husband, Peter (Chris Noth), which Czuchry lists as one of his favorite parts of Season 3. "There is a mutual understanding and a mutual respect that Peter and Cary developed," he says. "Cary looked out for Peter and Cary admitted he was wrong to Peter. There's definitely still potential for that relationship to continue." (But viewers won't learn why Peter was calling Cary at the end of the episode just yet. "That goes unanswered for the moment," Czuchry teases.)

Cary's extended time away also allowed room for his delicate friendship with Kalinda (Archie Panjabi) to evolve into something much more complicated. "That relationship has always been fun to play and there's plenty of room to grow with those two," Czuchry says. "One of the great things about Cary having been gone for two seasons ... is that that really gives a lot of currency to the audience in building that history. In Season 2, we saw Cary protect Kalinda. But in Season 3, we saw Cary was also willing to do his job when he put her in jail. That's a pretty wide swath in terms of what their relationship has gone through. And now that they're both in the same place, that relationship has a lot of potential to be an exciting one for Season 4."

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But the person Cary will have to worry about the most, it seems, is Will (Josh Charles), who Cary was forced to try to indict earlier this season. "Will and Cary are first and foremost good at their jobs and they're also both very ambitious people," Czuchry says. "In the first season, it was probably a pipe dream to think that Cary would get that junior associate position, but now with two years of cases on the other side, that is no longer a pipe dream. That really gives Cary a certain weight that he didn't have in Season 1, and I think that's bound to cause some tension for a little bit."

Cary's ambition is something to which Czuchry can relate. In addition to his long hours in the courtroom, the actor has been keeping busy off-set with his first book, Brothers On Life, which he co-wrote with his brother, psychology professor Dr. Mike Czuchry. "My weekends for the past 10 months have been spent writing this book and hiring editors and graphic designers," Czuchry says. "My brother and I have always loved storytelling, but we've written individually. Last June, it just felt like the right time."

That passion for storytelling is what makes Czuchry excited to explore the repercussions of Cary's return next season. "With Cary coming back to the firm, you create different windows and different dynamics with everyone," Czuchry says. "There's so much history because Cary worked with those characters and also worked against them. It creates a whole new dynamic not only in the firm itself, but just with each of those individual relationships."

The Good Wife season finale airs Sunday at 9/8c on CBS.