It was hours and hours of stuff. One of our producers was at [Ball’s daughter] Lucie’s house, and she pointed to a box, like, “What’s in that one?” It was very much a genie-in-the-bottle moment, finding all these audiotapes. When you’re doing a documentary, you realize that you and your editor [Robert Martinez, whose credits include “The Bee Gees: How Can You Mend a Broken Heart”] are like two people on a life raft. There was so much material, and that was by far the most overwhelming thing. Once we made the decision to hear Lucy and Desi tell us their story [via the recordings], everything changed, because not only did it make them feel alive and human, but we were able to age them as the film went on. Even though I strongly believe that most people are unreliable narrators, I think you learn a lot from what people don’t say, and it’s just as important as what they do say. I was always very moved by how they spoke about each other.

The film gives you the sense that on one hand, they’re upholding this very 1950s version of happily ever after, but that off camera, at least later in the marriage, they struggled. It’s sometimes hard to reconcile that with the Lucy and Ricky we see on television.

Television is an intimate medium that you often watch with your family, and they were the early inventors of the idea of rupture and repair, which is, maybe Lucy baked too much bread or Ricky forgot her birthday or whatever it is, and you think there’s no way they’re going to fix it, and they fix it at the end and everything’s fine. There’s a deep longing, especially in postwar America at the time, of thinking: “Can things be fixed? Are we going to be OK? Is the family going to stay together?” And what was really exciting to me is they were experiencing very human, complicated things that most people feel with success and marriage. You know, all the things that happen in a human life.

Did you have discussions with the producers or your editor about their marriage or about why their relationship might resonate with modern audiences?

Yeah, we really tried to deconstruct the idea of a partnership and ask questions about what makes a successful marriage. What Lucy and Desi do in their lives is they work very hard on themselves and their craft. They create this beautiful music together. And they go on to continue to create separately, respecting each other and finding ways to work together. So there’s always that question of, what is a successful partnership? Their marriage ends, but they co-parent and find new love. I loved talking to Laura LaPlaca [director of the Carl Reiner Department of Archives and Preservation at the National Comedy Center] because she said that America just didn’t accept their divorce. America was just like, nope. But they showed what it was like to get divorced and show respect for each other. They were blazing a trail. You know, if I had had the privilege to speak to either one of them, they probably would have just been living their human, complicated lives. They weren’t trying to do any of that.

Desi passed away in 1986. Their daughter Lucie tells a moving story about bringing them together to watch old episodes of “I Love Lucy,” which, in a way, is a little bit of a happily ever after, but very bittersweet. What did that story mean for you, and what do you think it says about their marriage and that notion of happily ever after?