The Tale. Photo: Kyle Kaplan/Courtesy of Sundance Institute.

Jennifer Fox’s The Tale (premiering May 26 on HBO) is a cinematic memoir of sexual abuse that’s pieced together before our eyes, with Laura Dern playing Jennifer Fox and Isabelle Nélisse her 13-year-old self — with whom Dern’s Fox eventually argues, across three-and-a-half decades.

With the word abuse I fear I’ve already misrepresented Fox’s complex ambitions. While I (and the legal system) define a “consensual” affair between a 13-year-old and her adult running-coach as rape, pure and simple, Fox argues for at least one shade of gray. Letting neither her rapist nor his female enabler off the hook, she wants to show how loved she felt, how much she chafes under the label of “victim,” even if she knows she was and, in important ways, continues to be. She wants to have agency. She tells The Tale in an attempt to take control of it, to make it hers.

The Tale’s genesis is a real, tender short story written by the 13-year-old Fox that her mother (Ellen Burstyn as a 70-something Laura Allen in flashbacks) discovers, reads with horror, and mails to her 48-year-old daughter. The grown Jenny reads it with a puzzled expression. Dern’s performance is fascinating, since she’s capable of emoting but must have known instinctively to go the other way — to play Fox as someone with a penchant for intellectualizing.

Jenny half-remembers the relationship but has consigned it to the more shadowed recesses of her mind. And here Fox pulls off a visual coup. The young Jenny we first meet (Jessica Sarah Flaum) is post-pubescent, plainly a teenager. It’s only when the older Jennifer hears herself referred to her as “so small” that she readjusts her perspective and the littler Nélisse enters the film. An affair with either of these Jennys would be statutory rape, but there’s a difference in the breed of predator.

The most unusual aspect of The Tale is that the male abuser isn’t the keenest focus of Fox’s memories. It’s the enabling woman — a tall, sleek English equestrian called Mrs. G, played by Elizabeth Debicki, who’s stripped down to chill elegance in short blonde hair. Fox introduces her via her smooth face, her ivory thighs, and an odd voice-over in which Mrs. G says that she’d never met any Jews before coming to America. Fox is a Jew, which adds that aspect, momentous but unplumbed. (Does it need to be plumbed? Hard to say.)

Jenny’s parents — relieved to be absolved of responsibility for the girl, one of five children — send her off to Mrs. G’s farm for a summer to learn that WASPiest of arts, horseback riding. At first, Jenny’s crush is not on the blandly handsome running coach, Bill (Jason Ritter), but on Mrs. G, it happens. But soon, Mrs. G and Bill are sitting with Jenny in a booth in a diner, confessing that they’re lovers (Mrs. G is married to a much older doctor, who’s barely seen), and offering to bring little Jenny into their special, extralegal, ad hoc family. Says Bill to Mrs. G, “I told you she was a deep soul.” And so Bill gradually propels himself to the forefront of little Jenny’s consciousness.

They are beautiful people. And they have a design for living that had currency in the late ’60s and ’70s, when people told themselves all sorts of self-serving lies — among them that repressive social norms (e.g., adults should not have sex with kids) should be flouted. The Tale has some — not enough — period ’70s flavor, but Bill’s counterculture cant about how people should be free enough to love whomever they want has unmistakable reverberations. You don’t have to be a reactionary to understand how progressive social movements can be co-opted by psychopathic opportunists. Their current incarnations are not so smug. Frances Conroy is the aged Mrs. G, whose façade has worn away and who can barely meet Jenny’s eyes. John Heard is the older Bill, a pillar of the community who might have continued his pedophilic ways — his history is shrouded. Or Fox chooses not to go there.

Parts of The Tale have a too-expository feel. A detective comes and goes to little effect. Jenny’s fiancé of three years (Common) is shown from a distance, as a bystander. And when Burstyn’s Nellie says she was afraid to act on her suspicions about Bill because she was “following her husband’s rules,” the revelation has no impact, because Jenny’s father (Matthew Rauch) was hardly ever in the frame. (I know Rauch and didn’t realize he was in this until I saw his name in the end credits.)

But Fox does well by her protagonists — both of them. Nélisse plays Jenny as a girl who feels empowered by secrets, and there’s an amazing exchange in which Dern’s Jenny tries to warn her younger self and the 13-year-old responds as if it’s yet another grown-up trying to muzzle her free will. Although a postscript assures us that a body double for Nélisse was used when Jenny and Bill are together in bed, there are shots of the girl’s face that show she thinks she’s truly loved — that she belongs somewhere at last. In the end, it’s not her conscious mind that breaks away from Bill and Mrs. G but her body, which “knows” what she can’t articulate. (One of the most important books about PTSD in the last decade is Bessel van der Kolk’s The Body Keeps the Score — an idea that’s all over this movie.)

As its title suggests, The Tale has its meta aspects. Dern’s Fox teaches documentary filmmaking, which means we get scenes in which she ruminates on the nature of storytelling and subjects her college students to a documentarian’s scrutiny. Yeah, I groaned, too. But there’s good stuff in those scenes beyond the obligatory thesis statement: “We tell ourselves stories in order to live.” If nothing else, they impel us to pay close attention to Dern’s affect, to the tension between the story Jenny wants to believe — that her 48- and 13-year-old selves are unconnected — and the one that she knows in her bones to be true.

Fox seems to be circling in on the possibility that her own detached, somewhat clinical aesthetic — the one that has shaped the film we’re watching — is the outgrowth of her adolescent trauma, so that The Tale is both a depiction and a symptom. That’s a tricky thing to capture, but it’s in the final shot, which can be read as an admission of failure. It’s the 48- and 13-year-old Jenny sitting side by side, spent, against the wall of a women’s restroom, together in their helplessness, with little to show for their pain except this extraordinary movie.