So Peter, you didn’t write “Ben Is Back” expecting Lucas to do it?

PETER HEDGES I very much believed that he would not be in a film of mine, and that he certainly didn’t need to be in a film of mine, with the way things were going. But with “Ben Is Back,” I did want to write something that both of my boys would be proud of, that they could look at and go, “That’s my dad.” I sent the script to Julia, she said yes, and when I talked with her, I came with a list of actors that could play Ben. And she didn’t ever want to see the list. She just wanted Lucas.

LUCAS HEDGES It would have taken a lot for me to want to do it, because I had no intention of doing it. But I heard people were receiving the script well, and I wanted to read it more as his son supporting him. So I read it late one night, and I was just really blown away by it. There was a part of me that was like, “O.K., maybe I’m going to want to throw my hat in the ring here.”

But you didn’t say yes right away. What was holding you back?

LUCAS HEDGES Just sheer discomfort. My dad giving me notes seemed just as uncomfortable as us talking about sex. But I sat with it longer and did the I Ching, a thing a lot of hippies did in the ’70s: You roll some dice and get your fortune told. I got really good results, and it struck me that the role was similarly special to Patrick from “Manchester by the Sea,” a part that I felt blessed to play. And I wanted to be of service to my dad in some way, during a big moment in his life. So I signed on, and it was hard and rewarding.