PARK CITY, Utah—“The story you are about to see is true,” says the protagonist of Jennifer Fox’s The Tale, “as far as I know.” That opening line of narration sets the stage for a movie in which the boundaries between fiction and nonfiction, past and present, agency and abuse are in constant flux.

Although the Sundance Film Festival’s catalog description didn’t give it away, it became clear that The Tale, in which Laura Dern plays a documentary filmmaker named Jennifer Fox, was pressed right up against the edges of truth, and if any doubts remained by the time the lights came up on the film’s shell-shocked audience, Fox erased them in the post-screening Q&A when she called the film “pure memoir.”

Knowing that it’s heavily based on Fox’s own recollections makes The Tale’s already tough story even harder to absorb. In the movie, Dern’s Jenny gets a series of increasingly alarmed voicemails from her mother, played by Ellen Burstyn, who has discovered a story Jenny wrote when she was 13. The story, called “The Tale,” is itself a thinly veiled fiction describing Jenny’s “special” relationship with her horse-riding instructor (Elizabeth Debicki) and her track coach (Jason Ritter), and its resurfacing opens up doors inside Jenny she had long since closed, memories she has either suppressed or rewritten. (That the film screened the day after Aly Raisman’s testimony at Larry Nassar’s sentencing hearing made its real-world resonance almost overwhelming.) She doesn’t understand the story, even though it’s a product of her younger self, but she can’t get away from it. “This is important to me,” she says, “and I want to figure out why.”

Knowing that it’s heavily based in the filmmaker’s own recollections makes The Tale’s already tough story even harder to absorb.

The secret at The Tale’s center is that 13-year-old Jenny was sexually abused by her coach, Bill (Ritter), who spends months lecturing her on the limitations of bourgeois morality and reading her Rumi poems before raping her. (This might technically be considered a spoiler, but it’s unlikely anyone will ever see The Tale without knowing as much, and given the film’s extremely triggering subject matter, it’s better to know in advance.) A prominent title card at the end of the film establishes that all scenes involving sexual contact with a minor were shot with an adult body double in the place of Isabelle Nélisse, who plays the young Jenny, and the film is more explicit about Bill’s intentions than his actions, but it’s still incredibly hard to watch. Ritter almost broke down in tears describing the shooting and had to turn his back to the audience for a moment to compose himself. But the most unsettling thing about his performance is its lack of any overt menace: Bill seems sweetly sincere, almost guileless, even as he’s grooming a 13-year-old girl for sexual assault. Even as the audience’s alarm bells are ringing, you can see how Jenny’s parents could have been taken in, sending their daughter off to spend weekends in the company of adults they trusted without really knowing. One of the things Fox wanted the film to do, she explained afterward, was to underline the fact that “the perpetrators aren’t monsters that you can pick out.”

The Tale’s most delicate negotiation is the relationship between adult Jenny and her teenage self—and by extension, between Fox and her understanding of her own past. As a teenager, Jenny is convinced she is going into her relationship with Bill with her eyes wide open.

Other adults might not understand what they’re doing, but she does. Jennifer’s boyfriend, played by Common, is horrified at her reluctance to label what happened as rape—an uncomfortable echo, for the few who’ve seen both, of a scene in Louis C.K.’s I Love You, Daddy—but she’s reluctant to let go of the idea that she was in control. It’s as if admitting she was a victim would be to victimize herself all over again. Fox said that it wasn’t until she was interviewing female friends for her six-part documentary Flying: Confessions of a Free Woman that she began to come to terms with what had happened to her. “I started to hear my story” from other women, she said, with half of them recalling some form of childhood sexual abuse. “It kind of blew my cover.”

The Tale’s Jennifer ends up literally interrogating her past: Her present-day self poses interview questions to Bill, to the adults who failed to stop him, and to teenage Jenny, who sometimes gets the upper hand. In one case, her past self corrects the present’s faulty memory. She’d remembered the story taking place when she was 15, and altering that detail forces the film to recast the role with a much younger-looking actress midstream. (Although films and TV often cast adults as teenagers, Nélisse was only 11 when she played the part; and no matter how teenage Jenny thinks of herself, the movie never lets you forget you’re looking at a girl, not a young woman.) Jennifer starts to see herself as a victim, but teenage Jenny fights back: “I am not the victim in this story. I am the hero.”

As she teaches a class of students how to navigate the tricky ethics of documentary-making, Jennifer quotes Joan Didion’s axiom “We tell ourselves stories in order to live,” but it makes you think long and hard about whether the “we” and the “our” are necessarily the same, and whether those stories have a cost as well as a purpose. The Tale instantly became the most talked-about movie of Sundance, and yet one of the festival’s storied bidding wars has yet to materialize, and whatever distributor ends up with the film will have to reckon with the fact that many people will be unwilling, or unable, to face it. But it’s almost impossible to conceive of a movie better suited to the present moment of reckoning with sexual abuse, and one better equipped to extend and complicate that extraordinarily necessary conversation.

The time for The Tale is now.

Read more about the Sundance Film Festival in Slate.