8 Things to Know About the 'All-Out Civil War' on 'The Good Wife'

When one door opens, another closes.

When Alicia Florrick (Julianna Margulies) opened her door to Cary (Matt Czuchry) at the end of last season, it set up a game-changing arc — one that will "rock everyone's world on the show," Margulies teased.

When Season 5 of "The Good Wife" premieres September 29, the two former rivals are teaming up to start their own firm. But breaking away from Lockhart/Gardner is going to lead to an "all-out civil war," as creators Robert and Michelle King have described it.

Here are eight things to know about the upcoming battles on the CBS drama:

1. The new firm is put on hold… for now.

Alicia and Cary, along with other Lockhart/Gardner fourth-year associates, are going ahead with the divorce — but there will be a delay. Alicia wants to finish up her current case, which has the firm scrambling to save a man on Death Row.

2. When the split happens, it will be nasty.

Cast and crew have described it as a "bloodbath," "gut-wrenching," "tumultuous," and "all-out civil war." And nobody emerges looking good, including Will (Josh Charles) and Diane (Christine Baranski).

"There are moments where people are going to hate my character and think she's just awful," Margulies told The Huffington Post, "and then literally the next scene, you're going to understand why she did what she did and hate Will's character and then it will flip."

Go behind the scenes of the season premiere of "The Good Wife" right here:

3. Alicia and Cary are not the new Diane and Will.

While they may be partners in this venture, there's too much history between Alicia and Cary for everything to go smoothly.

"It's not going to be completely blissful," Czuchry acknowledged to TV Guide. "They both feel like this is what they have to do at this point in their lives for different reasons, but that doesn't mean it's not without challenges and complications."

As Margulies said, "The uphill battle will constantly be, 'Did I make a mistake?'"

4. Being First Lady suits Alicia.

While she still shies from the spotlight, Alicia does like one thing that comes with being the Governor's wife: the power.

"It really challenges her moral compass as someone who always wants to do good, but it is incredibly provocative to be in a powerful situation," Margulies told E! Online.

5. Peter is tempted.

While Alicia relishes her First Lady powers, Peter (Chris Noth) will face what brought him down before: beautiful women. Melissa George has been cast as Peter's in-house ethics counsel. Can Peter stay faithful to Alicia… or will he be a very bad boy?

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6. A maverick shakes things up at Lockhart/Gardner.

Jason O'Mara ("Terra Nova," "Vegas") joins Season 5 in a big recurring role as "a wild-eyed Irish attorney" who has spent his career defending crime families. But his brash style clashes with the more conservative elements of Lockhart/Gardner.

7. Goodbye, Nick; hello to Kalinda's new love interest.

Nick who? Better to forget the story arc involving Kalinda's (Archie Panjabi) no-good husband. The Kings heard the negative fan feedback about the character and got rid of him. This season, Kalinda gets involved with an assistant state's attorney, played by Juliet Rylance. But knowing Kalinda, is this a real thing — or just a way of getting a sneak peek at evidence?

8. Bring on the guest stars (again)!

"The Good Wife" boasts the best guest star lineup in all of television, period. Emmy winner Carrie Preston will be back as the brilliant and kooky Elsbeth Tascioni. America Ferrera, Nathan Lane, and Gary Cole are also set to reprise their roles.

And even though he's headlining a new sitcom on NBC, Michael J. Fox made sure to include a clause in his contract allowing him to return to "The Good Wife." So his wily, manipulative Louis Canning can torment Alicia once more.

"The Good Wife" premieres Sunday, September 29 at 9 p.m. on CBS.