In the years leading up to World War II a new age of heroes began in the Marvel Universe. Courageous men and women stepped forward to fight the tyrannical forces of the Axis Powers, with valiant heroes standing tall against the regular Axis forces -- as well as their super powered and supernatural operatives. When the war ended, many of these heroes disappeared or retired from the heroic life. One hero who kept fighting the good fight into the 1950s and '60s was Margaret "Peggy" Carter, who many readers will recognized from Hayley Atwell's iconic portrayal across various Marvel Studios feature films starting with "Captain America: The First Avenger" and graduating to her own ABC television series earlier this year, the aptly named "Agent Carter."

Peggy served as a highly decorated resistance fighter during the war, and in the recently concluded "Operation S.I.N." miniseries writer Kathryn Immonen and artist Rich Ellis documented one of her first post-war exploits, telling a 1950s adventure that involved alien technology and a battle with a Hydra cell operating in the Soviet Union. This September, Immonen and Ellis reunite for another post-war Agent Carter tale tying in with Marvel's upcoming "SHIELD" celebration. The "Agent Carter: S.H.I.E.L.D. 50th Anniversary" one-shot celebrates the titular espionage agency's history by teaming Peggy with Lady Sif, the Asgardian god who starred in Immonen's run on "Journey Into Mystery."

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CBR News spoke with Immonen about returning to the characters of Peggy Carter and Sif, the role Howling Commando turned S.H.I.E.L.D. agent Dum Dum Dugan plays in her story, and Agent Carter's initial perspective on S.H.I.E.L.D.

CBR News: With S.H.I.E.L.D. celebrating its 50th anniversary, you and your "Operation S.I.N." collaborator Rich Ellis are being asked to return to Peggy Carter, a character you both have great affection for. Do you feel any added pressure given that the milestone adds an extra spotlight to the book and the character's place in the organization's history?

Kathryn Immonen: Any time you get to make stories with characters you love, it's a privilege and a joy but you're right, this is particularly wonderful. Creators often get asked what their character bucket list is and more and more the response has to do with creator bucket lists. The "Operation S.I.N." mini was the first time Rich and I had worked together and, as is typical with limited series especially, just when you feel like you're getting going, Carol Burnett shows up and starts singing to you. It's a terrific feeling for us to get another opportunity.

At what point in Peggy's history does your "Agent Carter: S.H.I.E.L.D. 50th Anniversary" special pick up at? What's Peggy's life like when your story begins? How much time has passed since we last saw her in "Operation S.I.N.?"

It's probably less than ten years on from "Operation S.I.N." and Peggy's been called in by Dugan in an advisory capacity. It all goes well and nothing gets broken.

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Which aspects of Peggy's personality are you especially interested in exploring in this story? How does she initially regard an organization like S.H.I.E.L.D.?

Peggy likes to be fully apprised of a situation. Being in control has maybe been the only thing she's been in control of and it's probably saved her life more than once. On a different day, I might come down on a different side of this, but here, she's really not impressed with the idea of S.H.I.E.L.D. It's maybe just a step too far outside jurisdictional oversight. Peggy's spent a lot of time operating at the fringes of protocol but she still knows how to wear the uniform.

You mentioned Dum Dum Dugan plays a part in this story. What kind of dynamic do Dugan and Peggy have together, and how substantial is his role in the one-shot?

Peggy meets up with Dugan on a S.H.I.E.L.D. ship, called in to provide her gut reaction to one of the most insane proposal's for a S.H.I.E.L.D. operative ever: Sif.

So Dum Dum is the catalyst for getting Peggy and Sif together at last and is not part of the main action of the book but Sif and Dugan both are responsible for turning Peggy on her head in this one. Peggy trusts Dugan, they've got history, they've built a solid relationship. Or so she thinks.

It's been a little longer since you last had your hands on Sif. How does it feel to tell a new story with the star of your "Journey Into Mystery" run?

I've missed Sif like crazy. I was entirely joking when I said to editor Jon Moisan, "Remember that time Peggy met Sif?" and he was all, "Let me check if we can do that!"

What is Sif like when we first meet her in this story? And how would you describe her initial dynamic with Peggy?

It's the Sif we all know and love, maybe a little less daffy than she ultimately ended up being when we wrapped up "Journey into Mystery." As for their dynamic, Peggy's awe is only outweighed by her bemusement. She mostly keeps a lid on both.

Let's talk about Rich's approach to this story. "Operation S.I.N." showed how great he is at period, spy action stories that involve all sorts of fun sci-fi weirdness. Can we expect him to stretch similar muscles with this story or will we be getting something different with this story?

Rich has a great feel for adventure. There is a lot of action in this story, a lot of gunfire, a lot of explosions. I'm just sorry that I didn't get more knives in. Next time.

Finally, it's clear you and Rich enjoy telling stories with Peggy. Any chance you're game for more stories featuring Peggy Carter?

I would go absolutely nuts for a Peggy Carter team-up ongoing!

The "Agent Carter: S.H.I.E.L.D. 50th Anniversary" one-shot is on sale this September from Marvel Comics.