What’s gone before is never really lost, but lingers in the air — or maybe only in the mind — like perfume, or its memory. That, at any rate, is the picture of personal history painted by “The Past,” the achingly melancholic follow-up to “A Separation” by Iranian filmmaker Asghar Farhadi.

True to its title, the past shows up, quite literally, in the film’s first few minutes, as a French woman, Marie (Bér énice Bejo), awaits the arrival of her estranged Iranian husband, Ahmad (Ali Mosaffa), in an airport. When they first spot each other, it is through soundproof glass, a lovely and effective metaphor for the paradox of access and intangibility that characterizes many acts of remembrance.

They’re not getting back together. It’s been years since Ahmad left France and his wife for his homeland, and the only reason he’s there now is to sign off on the divorce that Marie has, at long last, initiated. Marie, who has a little girl, Léa (Jeanne Jestin), and a teenage daughter, Lucie (Pauline Burlet), from a relationship that predates Ahmad, has met a new man, Samir (Tahar Rahim), who’s ready to move in with her.

Unfortunately Samir, as we discover in a story that peels itself, slowly, like an onion — and with just as many tears — also has a wife in a coma.

That particular circumstance is the point around which “The Past” circles, uncovering its narrative clues like a mystery thriller. Structurally, Farhadi’s screenplay sets up the kind of secrets, denials and shocking revelations that one would expect from a whodunit. Tonally, however, it’s pure relationship drama. “The Past” may have a gripping plot, but it’s more interested in the crackling, complex dynamics between Marie and her soon-to-be ex; between Ahmad and Samir; between Lucie and her mother; and between Samir and his young son, Fouad (Elyes Aguis), who’s consumed by a mysterious, burning resentment.

There are arguments, to be sure, but generally speaking, Farhadi keeps the level of emotion from veering into histrionics. A large part of that is due to Mosaffa, who moves through the film with a wise, sad grace of a peacemaker who has learned about war the hard way. More than anyone else, his is the character who sets — and keeps — the film’s mood of methodical discovery as he mediates between the film’s many moving, volatile parts.

Bejo (“The Artist”) is also quite good at evoking the pain of a character pushed and pulled in several different directions: by two men she loves (and who have — or who will — let her down); by an adolescent daughter who feels like she’s losing her mother; and by a little boy who already has one, and who doesn’t want another one forced on him.

Many thematic ingredients come together in Farhadi’s rich stew of a story: jealousy, resentment, betrayal, forgiveness, healing. The filmmaker stirs them, with the touch of a master, into a dish that both stimulates and nourishes.

More than those themes, “The Past” has something important and powerful to say about the past. It doesn’t shape or haunt the present. In a sense, Farhadi suggests, they exist alongside each other.

★ ★ ★ ★

PG-13. At Landmark’s Bethesda Row and Landmark’s E Street Cinema. Contains mature thematic material and some crude language. In French and Persian with subtitles. 130 minutes.