Starring: Scarlett Johansson, Adam Driver, Laura Dern, Ray Liotta, Alan Alda, Julie Hagerty, Merritt Wever, Azhy Robertson

Director: Noah Baumbach

THE film begins with a fake-out. Via voiceover, spouses Charlie (Adam Driver) and Nicole (Scarlett Johansson) enumerate the things, big and small, that they adore about each other: she’s an unparalleled listener, an expert gift giver, an “infectious” dancer; he’s a natural with their young son, a surprisingly great dresser, cries at movies.

Alas, those lists aren’t Valentine’s Day cards Charlie and Nicole have written for one another, or an intimacy exercise meant to draw them closer. They’re something a mediator has asked the pair to cobble together to kick off their separation in good faith.

This is a tough piece of work, steeped in pain that feels wincingly immediate (it’s based on writer-director Noah Baumbach’s own divorce from actress Jennifer Jason Leigh) and unsparing in its willingness to observe good people at their worst.

It’s also funny and, when you least expect it, almost unbearably tender, thanks in large part to the sensational leads, who deliver the deepest, most alive and attuned performances of their careers.

The juxtaposition of the film’s moony opening montage with the tense mediation scene that follows generates suspense: What went wrong between Charlie and Nicole?

The movie offers a chronicle of conflictedness, and of how a relationship changes — flails, explodes, evolves — over the course of divorce proceedings. Along the way, we grasp the dynamic that led to this particular marital collapse, but that is neither Baumbach’s point nor his purpose.

When we meet them, Charlie is a Brooklyn theater director and Nicole, having turned down a few lucrative offers in Hollywood, his company’s leading lady. After they split up, Nicole takes their 8-year-old son, Henry (Azhy Robertson), and moves back to her native Los Angeles to shoot a TV pilot. She spends time with her daffy mother (Julie Hagerty), a former actress herself, and sister (Merritt Wever). A new life starts to take form.

The challenge is figuring out where Charlie fits into it. Deciding to make their separation official, Nicole consults high-powered divorce lawyer Nora Fanshaw (Laura Dern). Staying friends with her ex-husband is the priority, Nicole insists. “We’ll do it as gently as possible,” Nora reassures her.

Nicole tells Nora her side of the story, recounting how her identity — her ideas, personality and ambitions — gradually became secondary to, and then swallowed by, Charlie’s. The substance of the monologue is familiar: A woman finds herself shrinking in the shadow of her husband’s ego and needs. But Baumbach shoots it in a few long takes, the camera slowly closing in on Nicole, and the whirlpool of feelings Johansson conjures — the nostalgia, the churning vulnerability, the currents of shame and self-loathing — is astonishing.

Nicole’s desire to spend more time in L.A. was a major point of contention during the marriage, and remains so during the divorce. Though his work is still in New York, Charlie — after meeting with two drastically different lawyers (Alan Alda and Ray Liotta) — establishes part-time residency near Nicole in order to negotiate shared custody of Henry. A new normal is established, with pickups and drop-offs, exorbitant legal fees and awkward conversations.

The exes still care about each other, as is illustrated by two moments of gentle heartbreak — one in which Nicole trims Charlie’s hair, another in which she orders lunch for him at a settlement conference. Among the movie’s most piercing insights is that divorce, even when necessary, isn’t always intuitive; sometimes it’s an act of self-abnegation, contrary to what the heart wants and requiring an almost cruel degree of discipline.

It can also snowball, taking on proportions of unpleasantness that dwarf or obscure the reasons it was pursued in the first place. Other American films about divorce have portrayed this phenomenon — the legal process driving and shaping the couple’s feelings rather than vice versa — but none with the force and clarity of this one.

With the attorneys nudging them toward more aggressive stances, Charlie and Nicole face off in an argument of soul-shaking vitriol, their grievances surging forth like scorching lava. As the problems of their marriage are laid bare (his reflexive selfishness and infidelity, her tendency to cast herself as a victim), the scene captures just how easily love can curdle into hate.

Baumbach has always been a master of high-toned cringe comedy, and there are laughs that leaven the mood here. A sequence in which Nicole’s mom and sister help her serve Charlie divorce papers is executed with giddy screwball snap. And when a poker-faced social worker (Martha Kelly) pays a visit to Charlie and Henry, the result is a stealth comic set piece.

Johansson makes you feel the clashing impulses and instincts in every step of Nicole’s transition into life without Charlie.

Driver has an even trickier task. Charlie isn’t an ostentatious narcissist. He’s affable, affectionate and self-aware. But Charlie has had an eclipsing effect on the woman he loves, and Driver delivers a brilliantly inhabited and shaded portrait of a man who’s forced to reckon with that reality.

(SD-Agencies)