By Jessica Michele Herring (staff@latinospost.com) | First Posted: Sep 07, 2013 11:34 AM EDT

"Vegas" star Jason O'Mara will be joining the plethora of powerful attorneys on the CBS hit "The Good Wife." 

According to TVLine, O'Mara will be joining the fifth season as Colin, an Irish defensive attorney who spent 10 successful years defending gang members and crime families. Colin now wants to go into corporate law, and is looking to join the Lockhart Gardner firm. O'Mara, an Ireland native, has also appeared on "In Justice," "Life on Mars" and "Terra Nova." 

The last season of "The Good Wife" ended with Alicia (Julianna Margulies) and Cary (Matt Czuchry) getting ready to say goodbye to Lockhart Gardner and establish their own law firm. While the prospect seems like a good idea, the pair will encounter some bumps along the way. 

Julianna Margulies told TVGuide that Alicia and Cary may not get along well as firm partners. "I think the biggest thing [will be] watching [Alicia] realize that her and Cary are not Will (Josh Charles) and Diane (Christine Baranski)," Margulies said. "The uphill battle will constantly be, 'Did I make a mistake?'"

Marguiles added that her actions will cause problems with her former employers. "There's going to be a lot of tension and a lot of friction and a lot of heartbreak," Margulies said. "Diane and Will will end up feeling, when they find out, like she stabbed them in the back. And she did." She also commented on Alicia's relationship with Will.  "I think we all know Alicia's heart was with Will and she never acted on it," Margulies said. 

Will, who is played by Josh Charles, may be leaving the show after next season,TVLine reports. Charles signed a new deal with the show last spring to continue playing the character of Will, but the deal is only for one year. Producers of the show are preparing for the possibility that season five could be his last. 

Robert King said that he is prepared for the possibility of Charles staying or leaving, despite the drastic changes that would entail for the storyline. "We can turn on, well, not a dime, but a 50-cent piece," King said about the show's direction. "We can turn things pretty fast if we need to."

"It's what Josh is about. He's someone who wants to always explore different sides of himself," King added. "And how [season five] goes helps him decide what he wants to do. That sounds like there's some contentiousness in our relationship. There's not. Josh is one of the friendliest and nicest actors I've met. Anything that is contractual stays with the agents." 

Although Charles' future with "The Good Wife" after season five is uncertain, it is confirmed that season five will include Charles, as well as a number of new guest stars. According to TVLine, Talia Balsam of "Mad Men" and "Homeland" will be joining the show as a featured guest star. Balsam will be appear early on in season five as a political journalist.

In addition to Balsam, Melissa George of "Hunted" and "Alias" has joined the show to play the recurring role of Marilyn, Governor Florrick's in-house ethics counsel. Zach Grenier, who plays David Lee, has also been upped to a series regular. Gary Cole, America Ferrera and Emmy-nominated Carrie Preston are also returning to the hit CBS show. 

"The Good Wife" returns to CBS on September 29. 

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