Starring Jodie Foster, 'A Private Life' is a character study in the guise of a thriller

She speaks in French but swears in English. It’s a cute way of clueing us in that Dr. Lilian Steiner, the American psychiatrist in Paris played by Jodie Foster in writer-director Rebecca Zlotowski’s “A Private Life,” hasn’t entirely left the U.S. behind. Lilian has lived and worked in France for decades, yet this divorced grandmother still finds herself needing to look up the slang phrases her young, upstairs neighbors yell at her when she asks them to turn their music down. (They’re blasting the Talking Heads’ “Psycho Killer,” which turns out to be an amusing selection on several fronts. Qu'est-ce que c'est?)

That sense of never quite feeling at home permeates Zlotowski’s film, a wry character study in the guise of a thriller. Lilian is the meatiest role Foster has played in some time, a buttoned-up, sarcastic shrink whose social graces have atrophied considerably, if she ever had them to begin with. She’s cold and aloof with her adult son (Vincent Lacoste), whom Lilian only calls on when she needs him to order the obsolete digital mini-discs on which she records her patient sessions — a technology I haven’t seen since the ‘90s. Hardly the world’s greatest grandma, Lilian times her visits to when she knows his newborn baby will be asleep so she won’t have to fuss over the child.

But the good doctor’s austere, carefully ordered existence is rocked upon learning of a patient’s suicide. She never saw any signs of this coming, which is deeply upsetting because that’s supposed to be her job. The widower (French national treasure Mathieu Almeric) is inclined to agree, chasing Lilian out of his wife’s shiva while snarling obscenities. In a screenwriting touch that’s perhaps a bit too cute, Lilian’s tear ducts begin to malfunction. Suddenly, she’s crying on the subway and in the middle of sessions. Not sobbing, just leaking. Her ophthalmologist ex-husband (the immensely charming Daniel Auteuil) insists there’s nothing wrong with Lilian physically, and a scarily convincing hypnotist thinks this all might have something to do with their past lives, an idea Zlotowski indulges to not entirely productive ends.

The problem is with Lilian right now. There’s simply no way she could have not noticed that a patient was contemplating suicide. Her entire professional identity rests on this, and since she doesn’t really have a personal life anymore, that’s all she’s got. So it must have been murder. It had to have been. Maybe it was the daughter who did it, though it’s usually the husband. After a bit of awkward snooping, Lilian discovers a large inheritance is in play. Soon thereafter, she and her ex-husband are traipsing around dark and stormy nights, acting like clumsy amateur detectives as old sparks reignite via some absolutely delightful chemistry between Foster and Auteuil.

“A Private Life” isn’t the kind of movie that usually spawns sequels, but I wouldn’t mind watching these aging exes solve a few more mysteries together. Auteuil has grown doughy and expansive the way European hunks tend to as they get older, unlike their gaunt and fitness-crazed Hollywood counterparts. He’s got a comfy softness that cushions Foster’s pointy features and flinty line deliveries. A tricky thing about divorced couples in movies is that you usually wind up wondering why they were ever together in the first place. But these two feel familiar in ways we instantly believe. There’s also something awfully sweet about watching a couple of 60-somethings get hot for each other again.

It's a kick watching Foster act in French. Thanks to her Francophile mother, the actress attended an immersion school as a kid, so she’s been fluent since she was a little girl. (One of the funniest parts of Rebecca Miller’s recent “Mr. Scorsese” documentary was old footage of Foster handling promotional duties en français for “Taxi Driver” at the Cannes Film Festival when Martin Scorsese and Robert De Niro were too distraught — ahem — to leave the hotel. Heck of a movie to send a 13-year-old kid out there shilling for, and she did so with aplomb.) Foster previously spoke the language during an unadvertised cameo in Jean-Pierre Jeunet’s “A Very Long Engagement,” a picture that screened for Boston critics the day after the Red Sox won the World Series in 2004. Let’s just say that some of us weren’t at our most astute that particular morning, and since I was still wearing the previous day’s clothes, I couldn’t be certain that Jodie Foster showing up and speaking French was something that had actually happened in the film until I went back and saw it a second time.

Zlotowski is throwing a lot of stuff at the wall here. The movie probably didn’t need to dwell so much on lush flashbacks to Lilian’s past life during wartime when she was having an affair with a previous incarnation of her deceased patient, no matter how dashing Foster may look as a tuxedoed cellist. But as her ex-husband points out, this steadfast woman of science falling for New Age mumbo jumbo is a sign of just how rattled she is by her failed perceptions regarding her patient. Lilian will believe a crackpot fortune teller or the most cockamamie murder theories, anything that can reassure her she wasn’t wrong.

“A Private Life” doesn’t always do right by its superb supporting cast, leaving marquee names like Aurore Clément, Irène Jacob, Virginie Efira and especially “Return to Seoul” breakout star Park Ji-min with precious little to play. Zlotowski does, however, make room for a honey of a scene with documentary legend and local hero Frederick Wiseman. In her previous film, “Other People’s Children,” the 96-year-old, part-time Cantabridgian played a kindly gynecologist who delivered the moral of the story. He’s got a similar job here as Lilian’s former therapist and mentor, the one person who can cut through her delusions by being even more brusque than she is.

Foster has spent her entire life in front of a camera, and she’s an unfailingly precise actress. This isn’t always to her benefit, as she can sometimes come off as too controlled. The key to her performance as Clarice Starling in “The Silence of the Lambs” — one of the all-time great movie performances, as far as I’m concerned — was that we were able to watch this young woman fortifying herself, brick by brick. The fun of “A Private Life” is watching all those walls come tumbling down. Foster is less poised in another language, especially when she switches back to English to swear. Lilian is obstinate, frazzled and, in the end, quite appealingly vulnerable. She spends most of the picture waiting for other people to finish talking so she can fire off a smart rejoinder. But we notice something different about her in the film’s final scenes. She’s listening.

“A Private Life” is now in theaters.