Here are edited excerpts from the conversation.

How did you first react to the role of Joan?

I was intrigued by it. I didn’t understand why she did what she did, because I think every female reaction would be, “Just leave him!” So I went into it with that question and step by step by step started to formulate an understanding and really love her. Figuring out her complicity in the relationship and how from the very beginning she didn’t want to lose him.

Do you have experience with this kind of unevenly weighted relationships?

I’m not going to go down on record with that. [Laughs] But I certainly observed my mother, who was married in the ’40s. [My parents] got married when they were 18, and my mom never graduated from high school. My dad went in the war and then became a brilliant doctor and it was all about him. And my mother basically sublimated herself to him, and we all watched it and loved her for who she was and for all her potential. She had this vague feeling of being a failure, of not having accomplished anything, and I understood it. And that kind of broke my heart.

Your first scene with Jonathan is almost startlingly erotic, especially for audiences not used to seeing an older couple having sex onscreen.

We talked about it. We didn’t ever get up on our feet and rehearse it but certainly by the time we did the scene in bed, it was very organic. I felt like we were two old pros kind of coming together, and it was like, “O.K., we’ll just do this.” I think it’s lovely that they’re so hot for each other in the beginning, and they have sex the first time you see them later in life. It just felt really real to me.

Your daughter, Annie Starke, plays Joan as a young woman. How did that happen?

Annie earned it. She did three screen tests and had a long lunch with Bjorn, so she got it herself. I was proud of her for that. And then she was very much part of the discussion before we started shooting because Bjorn shot their scenes first. She really did a beautiful job of establishing that character early on.