On last week’s episode of The Americans, we finally discovered why Elizabeth has been posing as “Patty” to befriend a chatty Korean immigrant and Mary Kay consultant named Young-Hee: Elizabeth is trying to get to her husband, Don, who can provide the much-discussed “Level 4” security code in order for KGB biochemical expert William to obtain access to deadly specimens. Played by stage actress Ruthie Ann Miles — who won a Tony Award last year for her performance as Lady Thiang in the Broadway production of The King and I — Young-Hee is a Season 4 standout.

Funny, warm, and independent, Young-Hee becomes a real friend to Elizabeth, who relates to Young-Hee as a fellow immigrant to America. In one episode, the two women talk about how much stricter their mothers were than they are. We see Elizabeth try out Young-Hee’s recipes at home, and call her up to go for a movie when she’s having problems with Philip. When Gabriel offers to ask the Center if there’s another way to get the access code, Elizabeth consents.

In order for viewers to believe that the steely Elizabeth would develop real affection for one of her agents, we need to be convinced that Young-Hee really is that fun to be around. Miles makes that easy to believe. Somewhere in between performing eight shows a week at Lincoln Center, she hopped on the phone to chat about Young-Hee’s sense of humor, re-learning the Korean accent she lost as a child, and becoming her mother.

Flavorwire: This is your first TV role, right?

Ruthie Ann Miles: Yes, it is. I couldn’t be having more fun. The camera actually makes me a little nervous, which is why it’s taken me quite some time to even get the courage to audition for television or film.

What did you know about the character at the outset?

They didn’t give me any idea of what the storyline was going to be. I started going through the news from 1983, about ’83-’85, because they were very specific — they wanted either Korean or Chinese, [they were looking] for people who could speak either of those languages. I thought, well, it’s gotta be about communism. Towards the beginning of shooting, I still didn’t know who this character was going to be, so I kind of left things open — just in case she ends up being a spy or just in case she ends up being a civilian. If I had given a look to [Elizabeth] here, that could pay off in episode 10 or whatever. It was like detective work.

What is it like to play a character who knows less than everybody else?

That’s really freeing. Because in The King and I, my character doesn’t have the voice that the king has, but at the same time she has responsibilities and so she has to make things happen in a quiet way. But with Young-Hee it’s very, very different. She doesn’t have all these huge responsibilities. She’s free to just be herself. She’s in America, where she can be an independent consultant for Mary Kay and make money for her kids. Her husband has a great job. She’s not restricted to being a stay-at-home mom. She has her fun — she makes friends, she goes to the movies. It’s very different from the character that I play eight times a week.

The character does feel like a breath of fresh air for the show.

There’s genuine happiness. And I think it’s really lovely to see Elizabeth absorb some of that. She definitely has a wall that she puts up against that, but you can see her hunger for it, and I think it’s really lovely and heartbreaking, also, to watch. [Young-Hee] shows a picture of a woman going to a foreign place and making a good, honest life for herself, and that’s the life Elizabeth has not chosen to lead.

Patrick Harbron/FX

Had you watched the show before you were cast?

I had, yes. I wanted to be a spy! I really wanted to play a double agent. But I could see immediately that Young-Hee was a very chatty character. Very fun. She’s witty and she has a good time trying to be an assimilated American. Those idioms, she tries to play with words — in Korean, we don’t have a lot of those sayings. She tries to joke, and she chooses hard words even though those letters might not be in the Korean alphabet.

Is there a specific phrase you’re thinking of?

[In this week’s episode] there’s a joke that she tells —it’s not a joke, it’s a family story but it needed to have this really funny punchline, and it doesn’t really punch at the end. She’s speaking it in her mind in Korean and it’s very funny, but when it’s translated it doesn’t have the same punch. It’s kind of a sad moment if you watch it in the context of what’s happening with Don and Patty/ Elizabeth.

How did you develop the accent?

My initial accent was closer to the one that I naturally would have had. I grew up in Korea for the most part until I was 5 or 6 years old. At home my mother only spoke Korean and most of my family spoke Korean. I had to work very quickly and very hard to break my accent.

When we started approaching how old Young-Hee was and how thick they wanted her Korean accent to be, I just brought the one that was natural to me. And they said, actually, we’d like her to be about ten years out [of Korea], not 15, 20 years out, which would be closer to where I am. So I had to go to my mom and say, “How would you say these words? What would be the easiest way your Korean brain would translate this into English?”

I wonder if your mom slipped into the character subconsciously.

Oh, yeah. I didn’t think so until I started watching some of the episodes. I would see my mannerisms coming out — even facial expressions of my mom as I said certain things, or gestures, little head nods that she does.

Young-Hee’s sense of humor stands out right from the beginning. I noticed just from watching clips of you being interviewed or your Tony acceptance speech, you seem to have a similar sense of humor. Did you talk about that with the writers or showrunners?

I only started thinking about that when we were filming the episode at the movie theater. So much of the wit and the humor that they put into Young-Hee is very natural to me, but we had never discussed any of it. But I got to know the writers during lunch breaks, on set, and I wonder, were they spying on me?

Have we seen the last of Young-Hee?

What I was told by J and J [showrunners Joe Weisberg and Joel Fields] was that this is a very common op for the KGB. They would infiltrate a family and get to know them and they’d get what they want and just leave them in pieces. So I wouldn’t be surprised if this is the last we see of this Korean family, just in pieces at the end.

Well, you’ve really bummed me out.

I know. I’m bummed, too.

The Americans airs Wednesdays at 10 p.m. on FX.