Aaron Staton as Ken Cosgrove: (Frank Ockenfels/AP)

Ken, the earnest ad man and promising under-the-radar author, made it clear that he opposes that decision. Then he insisted that he be assigned to the account. And he had another demand: “Pete doesn’t go to the meeting. And Pete doesn’t go to any meetings.”

What was motivating Ken during that conversation? I spoke to Ken Cosgrove — or rather, Aaron Staton, the actor who plays him — by phone Thursday afternoon and tried to find out.

During our conversation, Staton also discussed the impact of Peggy’s departure from the firm and answered the question that so many have wondered about: Did Staton ever watch “The Secret World of Alex Mack,” the Nickelodeon series that starred Larisa Oleynik, the actress who plays Ken’s wife, Cynthia? Here’s what he had to say.

In the scene last week between Ken and Roger. Ken responded to Roger in a smoother, savvier way than he did during the last big conversation with Roger this season. What’s going on with him in that moment? Is he becoming a bit more calculating?

Staton: It is definitely an interesting bookend, those two conversations, in a way. I think it’s that, you know, Ken has the power in that situation. I wouldn’t say that his savviness has grown, but the circumstances under which they were talking certainly were different. [Before] Roger came to him with this ultimatum and said, stop writing or I’m going to fire you. And there was nothing really for Ken to argue there. In this next position, he said, we’re going after your father-in-law. Ken is still opposed to the idea and his response is, okay, if you’re going to do it, these are my terms.

I just don’t think it’s savviness as much as the circumstances are different. Matt [Weiner, the show’s creator] said a few times that the theme this year, or one of the big themes, is that it’s every man for himself. Peggy’s gone. He had a pact. That was his sort of — that was not only his friend, that was his cohort. Now he’s dangling there, and he takes the opportunity to use the power he has.

That scene was so fun to shoot. I thought it was really interesting, too, to sort of see Ken to take that opportunity the way he did. He sort of seems like he has this impenetrable wall of happiness, in a way, he just seems to sort of rise above these things ... In the first meeting with Roger that you brought up, about writing, he said okay, I’m done. I love my job. I’m not going to write. And we see him later on, and he picks another name and moves forward. He forfeits the published works, but he continues writing, so he’s okay. But it was interesting to see that, you know, he used this opportunity to say that — well, what he really did was stick it to Pete.

Yeah, I wanted to talk about that, too. Pete has always seen Ken as a rival, but Ken always seemed less concerned about Pete as competition. Has something changed there? Why did Ken want to do that?

Staton: It’s interesting because, like I was saying, the reason Ken is able to maintain this happiness is because his ambition isn’t defined within the walls of the workplace. His happiness is in his family, and his hobby is in writing. Pete doesn’t have any hobbies. His home life is miserable. He’s miserable — he’s just a miserable person. But what he has is work. And he’s defined by that, Pete. It’s a good day when work goes well, and it’s a bad day when work goes badly. So I think that’s just a huge difference. To Pete — and I’m speaking for him, but it seems to me, anyway — it’s competitive, and it’s a competition, and every day at the work place, it’s kind of a kill or be killed kind of thing.

And Ken is there to do a job, so it just doesn’t seem to affect him the way it affects Pete. But given the opportunity with, you know, their history and the sort of — they have been placed in situations of competition, when they both were promoted to the same job and, ultimately, Lane had to pick someone. For the most part, Ken lets it roll off his back. But, yeah, I mean, I think the writing thing and all the years and — ultimately, I think the straw that broke the camel’s back, in my opinion, was the situation with Joan.

But you know, I don’t think it was directly that you did all of these things and you allowed this thing with Joan to happen so I’m going to take an opportunity to do what I can. I don’t think it’s as cut and dry as that. I think it’s complex. Pete’s power in the company is rising, and I think, you know, having him on this account and mixing that with his personal life — that’s his father-in-law — I think it’s more nuanced and it’s related to all of these things.

Does Ken have a longer plan in mind as far as why he wants to be the one on his father-in-law’s account?

Staton: Um. No, I don’t think he had time to really hatch any sort of plan, to be honest. It was pretty spur of the moment. And his first condition was that he just wanted to be on the account because if they’re going to do it, he’s not just going to sit back and let somebody else be in charge of it. He didn’t really have time to come in with any conditions; that’s just sort of what occurred to him. And in that moment, he said, I don’t want Pete there. Because... [long pause] Yeah. Just fitting in with that theme — every man for himself and I’ve got to look out for myself. And I think it's a better situation with Pete.

It’s interesting to see Ken, someone who normally lets things roll off his back, take this very specific approach and say, Pete’s not going to be involved.

Station: Yeah. Definitely, a shade of gray, in a way. But I still think, I can’t blame him, you know.

You mentioned Peggy’s departure earlier. There wasn’t much reaction to that in the episode that just aired because there were so many other things happening. Obviously, that had to have a huge impact on Ken. Do you know what that impact is?

Staton: I can’t say anything about Peggy, but I can say — well, as it related to that moment and that episode, I do know. It’s something that will — I can’t say anything about the future episodes, (a) because I couldn’t talk about the one that’s upcoming and (b) because I have no idea what’s following in the next season. But I definitely think that that’s — they’ve talked about it a few times. They had this pact, and she severed it. And so he’s got to take care of himself. And while he’s not defined by the office the same way that Pete is, it’s his job. He cares very much about it.

In that conversation with Roger, when Roger said, Stop writing or I’m going to fire you, [Ken] said, I love my job. And I think he does. I think he wants to protect it.

Regarding Ken’s writing: As part of formulating the character, did you spend time thinking about what he writes in his sci-fi stories, beyond what’s in the script?

Staton: You know, it was sort of, it was there in the story to me. I had a couple of conversations with writers on-set. I’d be lying if I said I was a big sci-fi fan myself, so I didn’t come in with knowledge of it. But it’s a really interesting genre because, and also it’s sort of another insight into Ken in that it’s very observational. It takes this context, which is pretty far out but has a way of commenting about this world and relationships and people. Giving it this far-out context, it’s more of a microscope than it is distance

And you see that when he abandons the genre entirely, and you see the snippet of this new story at the end of episode five, which is entirely about Pete and his sad world. To me, anyway.

I solicited some questions from readers, and several people wanted me to ask this: They wanted to know if you were familiar with “The Secret World of Alex Mack” and if you had seen it before you worked with Larisa Oleynik, who plays your wife.

Staton: My wife told me. I did not watch the show. But she told me, “Hey, that’s Alex Mack!”

For some reason everyone is fascinated by that. I’m a little old to have watched the show.

Staton: I know, that’s a show — me, too. I think I was just a little too old for the show. It’s sci-fi as well, right?

It was a Nickelodeon show. So kids’ sci-fi.

Staton: Kids’ sci-fi.

You mentioned earlier that you don’t know what lies ahead in future episodes. Have you had any conversations with Matthew Weiner about Ken’s general trajectory on the show beyond this season, or is it completely unknown to you?

Staton: It is completely unknown to me.

Is that scary as an actor?

Staton: No, not at all. It’s the opposite of that. This is the only series I’ve ever been a part of, but I imagine it’s something that’s so exciting about working in television. I mean, this show is just a dream. The stories are so real. There’s this real timeline, and it’s an actual timeline. And although the people are fictional, they grow along that timeline in such a realistic way that it’s so exciting to see what’s going to happen with these characters when we pick up with them in a year or two years. There’s just a journey, and it’s organic, and it’s affected by what happened in real life — the ’60s as they’re written in our history books — and also affected by these relationships that are created for the show.

(Frank Ockenfels/AP)

As an actor when you’re reading a movie or a play, you’ve got the beginning, middle and end in your hands, and there’s a bit of, you know, that’s the whole story. To know that your character has another year, as I think about, you know, as I look to my next year, there’s an infinite number of possibilities. It’s the same with Ken. It’s exciting because I know I get to go back and do that show again. Well, I hope.

That’s the thing. As we saw last week, sometimes people leave the Earth without knowing about it in advance. That’s the risk you take as an actor in general, I suppose.

Staton: Yeah. Right. There’s nothing ever [laughs] guaranteed, that’s for sure. In acting, I mean. Anyway, I’m just sort of stumbling through the same point. It’s just such a dream to be in a position to talk about a character going into a fifth season and the changes that have taken place. That’s just such a rare thing, I think. And on top of it, for it to be this show, it’s just an amazingly unique position. So I hope I get to do the same thing in another year. I think that was my point.

I follow you. Just one more question before I let you go: What are you working on during the hiatus?

Staton: My wife and I are expecting our second kid in 2 1/2 weeks.

Oh my goodness.

Staton: Yeah, we’re really excited. It’s been great to be able to take this time to hang out with her and my son and also sort of get things ready around the house

How old is your son?

Staton: He’ll be 2 — well, my second son--

Oh, you’re having another boy.

Staton: We’re having another boy. He’s due the 27th of June. And my son now will be 2 on the 29th. So they very well could have the same birthday.

Oh, wow. How crazy.

Staton: It’s been a really cool and fun hiatus.