Marnie screams for an operatic treatment. First published in 1961, Winston Graham’s psychological thriller features a woman navigating a world of men with murky motivations, a woman who discovers her own complicated emotional landscape while lying about it to those around her. Marnie swaps identities as freely as she changes hairstyles, embezzles from her employers and avoids intimacy at all costs. Rather than send her to jail, one employer, intrigued by this complex and brittle woman, blackmails her into a marriage and bullies her into sexual relations she finds repellent. Marnie’s deeply troubled relationship with her mother and her guilt over a traumatic childhood incident made her an obvious character study for Alfred Hitchcock, playing into so many of his own obsessions as a filmmaker.

When director Michael Mayer called me to suggest it would make a fabulous opera, my mind raced first to the Hitchcock adaptation. Strangely, though, I had just started dipping my toe into Graham’s novels. Michael and I asked Nicholas Wright to take on the libretto, and he said he had just read Graham’s novel himself. Then, not long thereafter, the serialisation of Graham’s Poldark novels began on the BBC. Clearly something was in the air.

In so many ways, Marnie reminded me of Mélisande, whose first line in Debussy’s opera Pelléas et Mélisande is: “Ne me touchez pas!” – don’t touch me. When her future husband interrogates her, she declares that “everyone” has hurt her, and that she cannot tell him in which ways. That sort of intense emotional ambiguity has always moved me deeply.

The three of us quickly agreed to focus on the book and all the subtleties and nuances that are missing from the movie, which cut or consolidated characters, changed locations and simplified plotlines. Nick created a lean, elegant libretto that preserves the lecherous and flash antagonist Terry, Mark’s brother (played by a countertenor) and provides a greyer, more subtle final scene, with Marnie facing a far from happy ending. The action, too, has been restored to London and Buckinghamshire, allowing a more true-to-the-text reading of the various class-based anxieties Graham deployed in the novel.

As I write this, ever more accusations about Harvey Weinstein swirl around and the UK’s Parliament is reeling from allegations of sexual misconduct. A year ago, a tape was released of Donald Trump boasting that women “let” him “grab them by the pussy”. Not long after that, while I was in the middle of writing the second act, Tippi Hedren published an autobiography stating that during the filming of Marnie, Hitchcock had sexually assaulted her.

Men in positions of power have a long history of such behaviour. One of the most difficult elements in Marnie is an act of sexual violence committed against her by her husband, Mark. Spousal rape has a convoluted legal history in many countries – while sexual harassment, sexual coercion and the boundaries of consent remain hotly debated issues everywhere. Graham’s novel walks a razor’s edge here, and Nick’s libretto follows suit. No character is unambiguously good or bad; everyone hides or denies their true selves. Marnie is both hunter and hunted. The journey she goes on is to know and understand her true self.

A huge musical challenge lay ahead: how to create an obliquely menacing atmosphere without reverting to Jekyll/Hyde or Madonna/Whore caricatures. I wanted to use music to indicate each character’s hidden intentions. A simple invitation to a poker game, a standard occurrence in a 1950s workplace, can become much more layered with the help of an orchestra. What immediately became clear was that each principal character had to be “twinned” with an instrument: with few exceptions, nobody actually tells the truth in the show, and individual instruments vying for position can reinforce the chamber music-like tugging between various deceits and agendas. For instance, when Marnie senses trouble, she can sing the casual phrases required of her, chipper and practical – whereas in the pit, the solo oboe tells us that she is trying to find a way out as quickly as possible.

In the second act, Marnie undergoes several sessions with a psychiatrist. I’ve long wanted to write such a scene, but the actual physical business of analysis is terribly untheatrical. So we created a quartet of body doubles for Marnie, meaning she could occupy the analyst’s couch while another actor fleshes out her story. This also solved another problem: how to take advantage of the wonderful ENO chorus in a way that doesn’t always reduce them to gang-like antagonism or gossip. Our chorus is freer to become a weather system in flux: here, office workers and typists; there, floating narrators offering comment on the nature of guilt.

The four Marnie doubles (who are called Shadow Marnies in the score, but are referred to by all as the Marnettes) exist as an all-female barbershop quartet, surrounding Marnie at times, representing not just her anxieties and her multifaceted nature but also her coping mechanisms. They sing in an early music style, with very little vibrato, and the score obsesses over the close intervals that cut through the larger vocal textures. The effect should be as if her inner monologue is actually a warped recording of the Tallis Scholars singing a single chord from an obscure Tudor motet.

Meanwhile we all agreed – composer, librettist, director, stage and costume designers – that the biggest logistical challenge would be staging the fox hunt, which is a climactic point in Marnie’s emotional journey. It’s simultaneously disastrous and somehow freeing, while being specifically linked to horses – which ruled out any clever substitution with something more practical, such as cars or small kitchen appliances.

I had an alarming vision of the chorus clacking coconut halves together in an endless procession across the stage. Mercifully, Nick reminded us that Marnie identifies with the vixen and then it became clear: set the whole thing from the point of view of the hunted. The dreaded coconuts become off-stage drums, operating like distant ominous thunder or undistinguishable noise. The shouts of the hunters and the braying of the dogs are abstracted into a huge cycle of pivoting chords, while what we see is the undersides of hooves, making us feel like we have our ears to the ground.

This is my third opera and I have learned something alarming: no matter how perfect things seem on the page, it is impossible to gauge impact and efficacy until one listens to the entire work sung by human beings straight through. I started writing Marnie in my small studio in Koreatown in New York almost four years ago, and only recently did we all turn up at ENO’s rehearsal studios in London for our first day. There is nothing as thrillingly touching as seeing the incredible amount of work so many people have done based on my scribbles: props, the beautiful set, the heroic acts of memorising by actors, a beautiful piece of stitching on a gown, performers learning the fiendishly complicated piano reduction. A year ago, I was the only person who had heard this thing. Now, hundreds of people are using it as a document, determining their daily labour for months.

Marnie herself remains elusive still. Do we ever know, can we settle on, who is a hero and who is a villain? As in real life, is there a bit of each in both Mark and Marnie, played by Daniel Okulitch and Sasha Cooke, who must tease out the impossible bond between their twisted characters? In the end, they are just like us: struggling to negotiate their best and worst instincts, including those they can control – and those they can’t.

• ENO performs Marnie at the Coliseum, London WC2N, from 18 November. eno.org.