For the most part, writer-director Sophie Fillières’ If You Don’t, I Will strikes an engaging tone of melancholic humor through its portrait of a French marriage slowly falling to pieces. Years into their union, Pomme (Emmanuelle Devos) and Pierre (Mathieu Amalric) are almost completely at odds with each other over every and any little thing; seemingly innocuous statements are laced with bitterness and accusations, and are thus responded to in an overly severe manner. They’re a pair whose compatibility seems to have melted away through familiarity, to the point that after an evening at an art gallery premiere, Pierre suddenly runs off to catch the bus and leaves his wife behind on the sidewalk.

Pomme and Pierre’s joint discord soon spawns individual disharmony, with Pomme repeatedly cutting her hands and falling in the shower, Pierre barely capable of looking comfortable in his own skin, and others (including their spoiled-brat son) regarding the two with bemused confusion, as when Pomme’s amusingly rude co-workers tell her that she looks different even though nothing external has changed. The revelation that Pomme has recently taken time off at work because of surgery for a benign tumor thus comes as something of an afterthought, since both her and Pierre’s problems run far deeper than her medical issue. A stew of regret, resentment, and anger has fostered their now-calamitous detachment, which Fillières visualizes through droll compositions in which her protagonists are frequently stranded alone in the frame, if not shunted off to its corners.

Fillières’ film somewhat falters in a middle stretch during which Pomme, finally fed up with Pierre while on a day-long hike, decides to stay in the forest by herself. It’s a decision that casts into sharp relief their isolation from each other, but which drags the proceedings’ momentum to a veritable standstill. During this sequence, If You Don’t, I Will suffers from the absence of back-and-forths between the superb Devos and Amalric, whose rapport—so prickly that a mere silent, lunging look from Pierre to Pomme speaks volumes about his coldness and hostility—is the material’s lifeblood. Moreover, during Pomme’s stay in the wild, her failed attempts to interact with animals result in unnecessary symbolism about her circumstances that further negate any of the preceding action’s discomfiting humor. Nonetheless, the film more than redeems itself at the story’s conclusion, via a protracted single-shot finale between its two reunited leads that’s a master class in low-key, and yet powerfully poignant, acting and direction.