At first "La Moustache" seems to be a darkly witty commentary on what we notice or don't notice about one another; we're so lulled by the predictable and the commonplace, it implies, that we fail to recognize change. Then it widens into a reflection on marriage and the notion that two people, no matter how intimately connected, inhabit separate worlds. An illusion of oneness requires each partner to overlook or deny the other's unknowable qualities.

This handsomely photographed fable is grounded in strong performances by Mr. Lindon and Ms. Devos, who are entirely convincing as a long-married, childless couple, whose relationship still has pockets of passion. "La Moustache" views events entirely through Marc's eyes. Agnès increasingly emerges as a headstrong, changeable enigma, not to be contradicted.

The film is likely to frustrate those who demand that a mystery be solved and wrapped up with tidy explanations. But its refusal to tie everything up in ribbons and bows is one of its strengths. Even after it finally exits the rabbit hole, and the Thiriezes find a tentative peace, unanswered questions and contradictions hover over their cozy rapprochement like anxious spirits.