"Moka" is a tense psychological thriller whose twisty plot benefits from a bravura performance by Emmanuelle Devos.
Devos' work will not surprise French cinema fans. Though not a household word over here, she is one of her country's top working actresses, best known for her Cesar-winning performance in Jacques Audiard's "Read My Lips."
With a formidable presence that mainlines emotional intensity, Devos dominates this film, appearing in almost every scene, but she has key support from another of France's most accomplished actresses: the enigmatic, four-time Cesar winner Nathalie Baye.
Devos and Baye — acting together in a film for the first time — have different but complementary energy, and their shared scenes, as structured by director Frédéric Mermoud and his co-writer Antonin Martin-Hilbert, are the film's strongest and most compelling.
"Moka" is based on a novel by Tatiana de Rosnay, whose earlier, equally coincidence-heavy "Sarah's Key" was filmed in 2010 with Kristin Scott Thomas as the star. From the moment we meet Devos' Diane, compulsively banging her head against a glass window, we can see she is a woman in trouble and in pain, but what kind of trouble and pain are not immediately apparent.
A patient at a private sanitarium, Diane almost immediately contrives to flee the place in Lausanne, Switzerland, just across picturesque Lake Geneva from Evian, France, and "Moka's" story shifts back and forth between the two cities.
Diane has been hospitalized because of the recent death of her teenage son Luc, who was killed by a hit-and-run driver while bicycling home from school. That death has understandably unhinged Diane, and "Moka" details the ways she deals with her overwhelming grief.
Both French and Swiss authorities are investigating, but that is going too slowly for Diane. And though everyone seems to agree that the death was an accident, Diane is determined to find whoever it was who drove the car. What form that confrontation would take is unclear, at least in part because the quest-obsessed Diane likely has not thought that far.
A detective she's hired tells her that the car, colored mocha (hence the title), was likely a Mercedes that came from the French side of the border and was driven by a blond woman. Armed with that information and a terrifying determination, Diane goes to Evian to find the culprit.
Almost immediately, she fixes on a mocha-colored Mercedes 450 SL. The car belongs to Michel (David Clavel), who works at a local spa, but the woman he lives with is the blond Marlene; as the potential driver, she's the person Diane focuses on at first.
As played by Baye, Marlene is complex, a self-described "self-made woman" who runs her own perfumery in town. Clearly capable but lonely, a bit estranged from Michel as well as her rootless adult daughter Elodie (Diane Rouel), Marlene is touchingly vulnerable to Diane's devious attempts to see if she was the driver who fled.
Too obsessed to leave things at that, Diane also insinuates herself into the lives of both Michel and Elodie, all with the goal of proving what she feels she already knows in her bones, that Marlene is the guilty party.
"Moka" makes it clear that Diane's mania means her instincts may not be accurate. Mermoud, aided by an unsettling score by Christian Garcia and Gregoire Hetzel, uses the strong cast to slowly ratchet up the tension. Though it demands periodic suspension of disbelief, as many thrillers do, this film's ability to unsettle us is undeniable.
Running time: 1 hour, 29 minutes
Playing: Landmark's Nuart, West Los Angeles