Christina Hendricks, <i>Mad Men</i> Christina Hendricks, Mad Men

Christina Hendricks fans, take heart. Joan is back!

Although the Emmy-nominated standout had a noticeable lack of screen time during Mad Men's third season, Hendricks promises a juicy season ahead for Sterling Cooper Draper Pryce's fiery office manager. "At the end of Season 3, there's a grand announcement from Joan's husband that he's joined the Army.  You will see a continuation of that story and watch that unfold a bit," she tells

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Indeed, Sunday's episode finds Joan and her husband, Greg (Sam Page

), considering starting a family, despite not knowing when he will ship out to basic training. Joan's visit to the doctor reveals some intriguing tidbits about her past, but it also shows Joan again putting on a happy face when she is perhaps anything but."She's trying to be a good wife and take care of this man who's clearly not who she expected him to be," Hendricks says. Let's not forget, before Greg's poor surgical skills ended his chances to become chief resident, he also raped Joan. But Hendricks says Joan's ability to mask such a terrible thing with a smile is what makes the character vital to the agency."There's all this turmoil and darkness and conflict going on in the office. Joan has a lot of conflict at home that she doesn't bring to the office, and therefore brings this levity and this light to the office," Hendricks says. "She has a sense of humor and is also very nurturing and takes care of these other characters. ... She just keeps plugging along and trying to make things work. There's something very positive about her in that way."

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Hendricks, 35, believes the new office set was built to accentuate the importance of Joan's role in the day-to-day business. "Joan's office is smack-dab in the middle of everyone else's, surrounded by glass," she says. "She's in this fish bowl, but she can watch over everybody."In fact, Sterling Cooper Draper Pryce may have never gotten off the ground at all, if Joan's former lover, Roger Sterling (John Slattery), hadn't made a well-timed phone call in the Season 3 finale. But Hendricks cautions viewers not to automatically assume there will be a resurrection of that affair."Those characters have worked in the same office for 10 years, so they have a lot of history. When things are about to go down, Roger really knows the best person to call, whether it's about a more intimate relationship or not," Hendricks says. "The fact is that he trusts her and she knows that. It's always going to be there between the two of them."Mad Men airs Sundays at 10/9c on AMC.