An open marriage is always destined to end in recrimination and tears, I should know, says BEL MOONEY

Try to imagine the scene. Your two young sons are asleep, you’ve had another day of being the perfect mother. You love your husband very much, and he loves you.

Your sex life with him is excellent, even after ten years. In fact, it’s hard to imagine a better marriage. . . and yet. And yet you want more. You long for exciting sex with that man you met in the bar, the one with the slim hips. . .

Tormented by desire and the urge to break away from domesticity, you confess your desire for sex with another man to your husband.

His easy response turns your world upside down. He says, “You can date him again, as long as you tell me everything.” You realize that he wants to reveal details about your sex with other men. Oh, and he reveals that he wants to sleep with other women too. Tit for tat, you might say.

Does this come as a shock to those of you in committed relationships? Could you do it? Would you ever want to open the door of your marriage to let others in?

In the early 1970s, the concept of “open marriage” was hot – and some of us even succumbed to the theory that it is possible to both stay and stray.

Marriage should not be a prison, we shouted. We heard Black Panther Bobby Seale’s rallying cry to “seize the time” and we considered personal sexual freedom a human right. Away with your repressive, bourgeois morality!

People like me (on the left and yet living a privileged life) worshiped Jean-Paul Sartre and Simone de Beauvoir – intellectually united, yet remaining unmarried and free to openly participate in any number of relationships.

Not that there are such pretentious theories in More.

The author and her husband, Stewart, are the next generation: our children, Generation X.

No political attitudes for them, only sexual ones. With a minimum of discussion, they agree to their open marriage with astonishing ease. Molly has fallen in love/sex with Matt, who in turn feels guilty for betraying his girlfriend. But Molly doesn’t have to feel guilty for only doing what Stewart agreed to. Meanwhile, he is dating another woman. . .

If it sounds like a complicated mess, that’s because it is. I’ve been there: the moment when you say goodbye to the spouse you love and ride to the loved one’s bedside. All very 1970. And Molly’s account reads like a confessional from Cosmopolitan magazine of that time. Yet this book is a story about 21st century New York. The consensual infidelity that Molly and Stewart have chosen is, she explains, “a double life.”

“In one lifetime, I wake up early in the morning with the kids, make breakfast and pack lunch, arrange pick-ups and playdates, cook dinner, run the bath, read bedtime stories. I go to sleep and sing lullabies.

In her book, Molly Roden Winter identifies “the void” in the lives of many women as “a need for something that marriage and motherhood cannot fill.”

‘I greet Stewart when he comes home late at night, give back massages or make love, and sleep next to him. I am the image of the dutiful mother and wife – but only in service of my other life, the one in which I think of Matt. I imagine what he’s doing and who he’s with. I wonder if he thinks about me too.’

What is happening? Like many women (even if they don’t admit it), Molly Roden Winter identifies “the void in my life” as “a need for something that marriage and motherhood cannot fill.”

She wants ‘to be seen with fresh eyes’ and recognizes her desire as ‘not to feel like a woman or a mother anymore, but a desirable woman again’.

In the film of this book (which will undoubtedly be made), this is the reason for Try A Little Tenderness on the soundtrack.

But no matter how many women have those feelings, few want the complicated life this book describes.

Molly has returned to teaching and is a good wife, mother and daughter to elderly parents, who (she discovers) had a kind of open marriage of their own.

This is almost the most fascinating part of the book. A therapist suggests that there are two sides to her: the ‘Straight-A Molly’ who always did what she had to do, and the other Molly, the ‘badass’ woman who wants to be seen with her own eyes, who wants to cross boundaries.

But neither of those “two” Mollys can stand it when Stewart has sex with another woman (his ex, to complicate matters) and hates the cool way he reminds her that she has “consent” to him datum.

They have set some ground rules for their respective interactions, including not falling in love with any of the other people. Very wise. But how can you be sure you don’t?

Matt lasts four years of shame (her), guilt (him) and good sex. There’s a little more angst on the author’s part, but she decides she still wants to “expand my sexual horizons.”

A dating website offers Mike, who is a failure; Leo, who is kinky; weird Laurent; then Liam. Meanwhile, Stewart has four wives at once, and Molly takes advice from a book helpfully titled The Ethical Slut.

When the dating site offers Karl, Molly gets into trouble. She likes him too much. Is this love?

It turns out that Karl’s partner, Martina, is a female version of Stewart and wants to know all the details of his sex with Molly.

So the affair continues until Molly is talked into having a rather awkward threesome with the two of them. And then she fell. Next up is a meeting with Scott. But enough!

More is a compelling book, but it leaves you wondering what this couple has in store for each other in the future. They are still crazy about each other – and the book is dedicated to Stewart. Yet there is a whole other book that begs to be written, about their two children for example, and what damage can be done to them.

An open marriage is all very well when you’re young and irresponsible, but – take it from me – growing older usually brings recriminations and tears.