Henry James, that Mandarin stylist of 19th-century American letters, has long been a prisoner of the Masterpiece Theatre ghetto. The smart, sleek film “What Maisie Knew” liberates his 1890 novella, a disturbing story of emotional violence surrounding an upper-class London child-custody dispute.

The film relocates the drama to present-day Manhattan. Instead of self-involved aristocrats, the not-so-noble players are Susanna, a fading rock star (Julianne Moore, never better), and Beale, a manipulative art dealer (Steve Coogan at his most insinuating). The manners of the leisure class have transformed. The nature of emotional warfare endures. A century after James’ death, nothing essential has changed, as if we are fated to commit, and suffer, the same cruelties.

The film is true to James’ spirit, as psychologically probing as his baroque prose, and a lot easier to digest. The central character is the unhappy couple’s daughter, Maisie, a 6-year-old moppet played by the magically talented Onata Aprile. From the first half-overheard argument that greets the waking girl, the story unravels through her perspective. The child works to grasp adult issues that are all too clear to us.

Susanna, with her noxious temper and fame-coddled ego, is a catastrophe as a parent. Beale retreats behind a shield of sarcasm and constantly travels to escape a situation he can’t deal with. Maisie looks on as the lock on the apartment door is changed while daddy is away.

Maisie is played as a pawn as divorce hearings approach. A young friend of Maisie’s, whose mom might be recruited as a character witness, is invited to a sleepover. Susanna’s hard-partying hangers-on create a ruckus that sends the girl home in tears. Beale ups the ante, abruptly marrying Maisie’s pretty, responsible nanny, Margo (Joanna Vanderham). Surely that will convince the judge that he’s prepared to provide Maisie a stable home. Susanna retaliates with a quickie marriage to Lincoln (Alexander Skarsgård), a weak-willed bartender.

Maisie learns to see through the adults’ charade. Her mother forgets to pick her up after school, and a lesson is learned. When she observes Beale throwing away an emotionally significant floral bouquet from her mom, she rides her little bike in circles on the balcony. It’s as if we can see the gears turning in her head. Her parents will fight over her, but not fight for her.

Maisie can also see the good in grownups. Her new stepparents, who are also her parents’ victims, mean well. Even though Beale is as horrible to his new wife as he was to his first, Margo makes a loving environment for his child. Lincoln fills the void left by Maisie’s neglectful mother, who snaps, “You don’t get a bonus for making her fall in love with you.” Maisie, with a child’s wisdom, opens her heart to those who will value it.

Co-directors Scott McGehee and David Siegel infuse the film with energy and emotional intelligence. The color scheme is as vivid as a box of crayons. The Manhattan locations percolate with vibrant life. Each character gets his due. Even Susanna, greedy once again for Maisie’s affection, tries to win her back. The gesture can be read as sincere contrition or the performance of a woman who postures in a spotlight for a living. Here, in Coogan’s spooky silences, and in the hypnotic performance by its young star, this film takes us to the very heart of acting. The story is sad, but the talent involved in its telling is elating.