Olivia Colman and Jessie Buckley never share a frame in “The Lost Daughter,” since they play the same character, Leda, a literature professor and translator, at different and equally challenging ages.

But for anyone who considers these two to be among our very best screen actors, as honest and exacting as they are supple and versatile, the satisfaction of seeing Colman and Buckley create different stages of the same life is enormous. Taken from Elena Ferrante’s 2006 novel, first published in Italian, “The Lost Daughter” is a triumph of adaptation for writer and first-time feature director Maggie Gyllenhaal. Her film, relocating the novel’s southern Italian setting to a Greek island, spins a subtle web of intrigue.

“Subtle,” however, doesn’t mean calm. Leda is not one of those reader- or audience-placating figures designed to cope with a couple of neatly spaced setbacks and then get on with the triumph-of-the-human-spirit part of the story. Gyllenhaal’s film, one of 2021’s essential character studies, makes its Netflix streaming premiere Friday, in the same trough (sorry, “platform”) where a mediocre agitproppy comedy starring Leonardo DiCaprio and Jennifer Lawrence is currently sucking up all the oxygen. I mean, see them both; it’s your subscription. But see “The Lost Daughter.”

Leda arrives to her vacation destination alone, which for her is customary. She is in her late 40s. Early on, director Gyllenhaal and editor Affonso Goncalves flash an image of Leda’s younger self, played by Buckley, and one of her daughters. Also early on, Leda talks — frustratingly briefly — to one of her two now-grown (and unseen) daughters by phone.

Welcomed to the modest island resort by American caretaker Lyle (Ed Harris, pitch-perfect), Leda enjoys her solitude, and the occasional interaction with Lyle, who, like Leda, is a loner by temperament with grown children. Leda also meets a young Irish resort employee (Paul Mescal, equally good), whose life has yet to find a clear map.

Gyllenhaal’s adjustments to Ferrante’s novel aren’t structural but they too are strategic. The Leda of the novel is more violently out of control in the flashback scenes; the movie’s version keeps the edges but strikes a greater variety of chords. In the book we learn more about Leda’s own childhood despair. Gyllenhaal’s only real misstep, I think, is reaching for a more unreservedly affirmative coda, too abruptly.

At various points in Ferrante’s book Leda puts things a little more bluntly than Gyllenhaal’s adaptation favors, again for the better.

“I seemed to be falling backward toward my mother, my grandmother,” the book’s Leda says, “the chain of mute or angry women I came from.” That’s a first-rate line, and many like it remain in Gyllenhaal’s screenplay. But her filmmaking instincts are shrewd in “The Lost Daughter,” shaving off as many of those lines as she keeps. Gyllenhaal’s work with her actors is quietly spectacular, and she takes the best of Ferrante’s fearlessness while letting Colman and Buckley unfold the character’s secrets through action and reaction.

Actors turned directors generally learn a lot along the way, watching how others work (or don’t) with performers. For years, on the other side of the camera, just like Rebecca Hall (“Passing”), Regina Hall (“One Night in Miami … “) and other triumphant debut filmmakers, Gyllenhaal has kept a close eye on what brings out the best in a scene, and in a story worth telling, with morally imperfect, fully dimensional, persistently human characters. I suspect even a so-so adaptation of “The Lost Daughter” starring Colman and Buckley, with the same unerring supporting cast, would’ve likely been worth seeing.

As is, we don’t have to settle for so-so.

“The Lost Daughter,” in theaters and streaming on Netflix, is rated R by the Motion Picture Association of America for sexual content nudity and language. Running time: 120 minutes. Four stars out of four.