As I talked to couples over the last year, I often found myself reflecting back on my own marriage. I started to feel less baffled by the boldness they were showing in opening up their marriages, and more questioning of my own total aversion to the possibility. In interview transcripts, I saw that I was forever apologizing for my own conventionality. I felt, at times, that I was a rusty caliper, trying to take the measurement of some kind of advanced nanotechnology. I was a blunt instrument, or a chipped mirror: Where I discerned motives of retaliation or evening of scores, I was told to see generosity and understanding. Where I read humiliation into a situation, the people I was interviewing saw a kind of expansive love that defied pride, possessiveness, traditional notions of masculinity and ownership. I kept wanting to define terms — but who is your primary? Whom would you choose in the event of conflicting needs? My instructors were patient but resolute in their overarching easygoingness: It works out, and when it does not, we talk about it and are better for it.

Open marriages, I started to think, are not just for people who were more interested in sex, but also for people who were more interested in people, more willing to tolerate the inevitable unpacking conversations, the gentle making of amends, the late-night breakdowns and emotional work of recommitting to and delighting each other.

Few claimed there was no pain in nonmonogamy; but they were not afraid of that pain, whereas the notion of any extra pain in my life seemed an impossible burden, a commitment along the lines of taking on a second part-time job or caring for an ailing parent.

Occasionally, my reporting would inspire me to turn to my poor husband: Why don’t we work more on our marriage? But more often than not, I felt protective of what we had, more certain of its beauty, its cosseted security. I imagined our marriage transpiring within a genie’s bottle, all silk and luxurious hangings in a protective cocoon, a warm, private world in which transformation could occur; the nature of the surrounding boundary providing enough safety that we could feel confident in taking risks. Breaking out of that cocoon would be an act of needless destruction, its violence transforming the retreat into a hornet’s nest. But there was something about that idealized vision of the cocoon that seemed contrived; was it also cloying, or confining, or implicitly fragile?

In February, Daniel planned a weekend away with the woman he saw the previous month — his girlfriend? His date? Neither word felt exactly right. He still felt concerned, both about how Elizabeth was going to feel about the weekend upon his return and about how he would feel in the midst of it. “I was nervous about how I was going to be received, and how I was going to handle it emotionally,” he said. Even the thought of being naked in front of someone new gave him pause. “There’s a little hesitancy — like, what is she going to think? But I think in the end when you’re with somebody who is compassionate and interested in you as a person, that all quickly just goes away — because, look, we’re all people, and we have our flaws and our good parts, and you either dwell on those things that aren’t perfect, or you see beyond it.”

They ordered grilled cheese from room service and ate it on the couch as they talked about why they were there. They smiled at each other quietly as they sensed the attraction building. “And then we kissed, and honestly, it felt good,” Daniel said. “It just felt like, wow, I can be in this moment, and feel this other person kissing me, and me kissing them, and I feel I can do so in a way that is not violating my marriage and my commitment to my wife.” They had sex several times over the course of the weekend. Emailing about it, several months after the fact, Daniel wrote: “It was good, very good. ... As I write this, I am taken back to the moments there, and it does evoke a flood of stark imagery, emotion and sexual desire. ... There were no expectations or history to draw from. She was not afraid to express what she wanted, and in doing so, she challenged me to show up in ways that I don’t regularly — mainly in a more aggressive and dominant way. I guess what I’m saying is that it taught me some very valuable things about myself, or maybe invited some aspects of myself to come out.”

Elizabeth claimed to have no ambivalence about his weekend away. She said she knew from experience that an outside relationship did not have to diminish your love for your spouse. And yet when Daniel returned, he found her a little bit cold, judgmental not about the premise of the weekend, she said, but about the particulars. She and Joseph had waited for months before having intercourse, building the relationship first; Daniel did not wait, which bothered Elizabeth. Also, Daniel had called her to say hello, which she had not expected, then jumped off the phone for a work call and failed to call back. That she did not like — the feeling that he had engaged her, almost deliberately, and then left her hanging, as if to force her to concentrate on him in his absence.