Last night’s episode of Mad Men was called “Far Away Places,” and perhaps no one traveled as far as Roger Sterling, the veteran ad man who, along with wife Jane, took his first LSD trip. Slate spoke with John Slattery, who portrays Sterling, this morning.

Slate: When you first read the script, did the acid trip surprise you?

Slattery: I guess it did a little—although, you know, the scripts are always surprising. I think it’s interesting that of all the people that could have taken LSD or had that experience, that it was Roger.

Slate: Part of the genius of the show is that things happen to the least expected characters, and yet those things feel plausible and believable.

Slattery: It’s also not like they pick a name out of a hat. I think it has to do with where his wife was in their relationship. Maybe he was the character that needed it the most.

Slate: That was one of the other striking things about it. Roger Sterling often seems like a man from another era, and, in the first few episodes this season, it seemed the world was changing and he wasn’t changing with it. And then suddenly this episode comes along, and maybe the changing times won’t be as hard on him as we thought.

Slattery: I think you see the shift in all these characters starting. Peggy’s life is changing. I thought it was interesting when she had that unsuccessful pitch to Heinz, and she comes in and does what Don did in the pilot and stares at the ceiling on Don’s couch. You can see these characters overlapping and changing and almost becoming one another.

Slate: During that LSD trip, Roger sees Don in the mirror and later he sees Bert on a dollar bill. Did you have direction from the script as to how to respond in those moments, or did you need to come up with on your own sense of why he was seeing those things and how he would react?

Slattery: That was all in the script that Scott Hornbacher directed. That was a very difficult sequence to put together. And there were things that were cut—some jokes. I think they were smartly cut, because there were a lot of gags, and I think the whole trip was less jokey in its final form, less joke-filled than it was on the page. Which is smarter, I think, because it would have been just a series of gags.

Obviously we have a very short time to put all this stuff together. There were a lot of special effects they have to lay over—a gag where Roger’s cigarette shrinks, and then the mirror stuff. Looking down at the bill and then looking at her in the cab—you know, it’s all on a stage in the car with a green screen, and them talking us through the beats—“Now look at the bill, now look at her.” And it was all really specifically laid out—the music coming out of the vodka bottle was there in the background. I took the cap off, and they played the music. I put it back on, and it would shut off. So they do everything they can to help you out.

Slate: And does that include saying, “OK, so you’re looking in the mirror, and you see Don, and you’re feeling this.” Or is that more up to you?

Slattery: Well, I’m acting the scene, so I’m playing it, and then the director comes in and says, “That’s good. Now try less anxious.” Or, “Try one where you’re just having a conversation.” It’s really just a series of adjustments. But it’s interesting, the room for interpretation that everybody has—the actors, the directors, the cinematographer, designer. You know, everybody’s expected to put their stamp on it. So, that’s what we’re all trying to do while telling the same story.

Slate: At one point on that LSD trip, Roger is in the tub with his wife, and he starts seeing the 1919 World Series and bursts out laughing. Did you develop in your own mind some idea this as to why he was seeing some old baseball game—and why it was so funny to him?

Slattery: I mean, you have to find something that amuses you to the point where you’re pretending to watch the 1919 World Series, which I never saw, when you’re just pointing at the crew, basically, and laughing, in a bathtub of cold water with a few people staring at you. And, actually, we reshot that scene. Matt decided he wanted it to be funnier. He wanted me to be more amused. You know, he always has a really specific vision of what he wants, and I think since he had the chance to reshoot it—since the schedule has been different and our air date is further away from production, he’s had the luxury of changing things if he thought it was necessary—we reshot that scene.

Slate: Did that then change your own sense of who this guy is—or do you not think about the character in that way?

Slattery: There’s a core knowledge at this point—all the scenes that you’ve played as this person exposes a core knowledge, and there aren’t many wrong notes. I suppose the wrong notes sometimes come in direction, because the writing is fairly consistent. But sometimes when someone comes in and says, “What if we try it like this?” it doesn’t feel right. So I guess the knowledge of the character comes in when you think, “Well, maybe a character wouldn’t do this.”

Slate: When something like that happens, when a director says, “Let’s try it this way,” and you think, “Eh, that doesn’t really sound right to me in terms of how Roger Sterling would act,” is there room on the set for you to say, “Hey, I don’t know if that makes sense?”

Slattery: Yeah. Matt and the directors respect our input. However, a lot of the direction comes from a tone meeting or a discussion prior or an understanding between the director and the producer that this is what they want from a scene—so you know it’s coming not just from the director. But some directors don’t have as much experience with the show as we do, so you sometimes have to read between the lines and figure out what’s coming from where, and sometimes you have to protect yourself.

Slate: You’ve directed a few of the episodes yourself. Did you learn something from directing that was different from what you’ve learned acting in it? Did it provide a different kind of insight?

Slattery: It does give you a chance to see how well put-together it is by everybody. And it does illuminate the need for different interpretations from take to take. There’s no point in doing it the same way five times, because then you get in the editing room, and you’ve got nothing to work with. So you have to allow directors to have an interpretation—you’re the person they’re working through. So when someone says to try playing it a little less amused or a little more amused, you have to be open to that, because you’re really only part of the story.