"The Past" is a deliciously soapy French romantic mystery, a melodrama that gives that label a good name.

It’s about divorce and the rippling waves of pain caused by it and the affair that precipitated it. And the more we learn about who did what to whom and when, the more intriguing it becomes.

Ahmad, played by Iranian actor Ali Mosoffa, flies in to Paris and is met at the airport by Marie (Berenice Bejo of "The Artist"). There’s a warmth in that meeting, but something’s a bit off. We start to figure it out on their drive home.

He’s been gone for four years. They were married. She’s ready for a divorce. That’s why he’s come back.

The brittle undercurrent turns more tense when he arrives at what used to be their home. Marie’s daughter by an earlier marriage, Lea (Jeanne Jestin), remembers him. But there’s a strange, hostile little boy, Fouad (Elyes Aguis). Marie, it turns out, has a new beau and Fouad is his kid.

And Marie’s other daughter, Lucie (Pauline Burlet), a soulful, sad-faced teen, cannot stand that new man mom wants to marry.

Ahmad finds himself sucked intoa complicated domestic mess involving Lucie, Marie and Fouad’s father, Samir (Tahar Rahim). Yeah, mom took up with another Iranian. Paging Dr. Freud.

Samir already has awife. She’s in a coma. And Ahmad cannot hide his unease at every fresh tidbit that someone adds to the mix, while Marie has trouble masking her guilt over what she and Samir are doing or may have done.

n

Veteran writer-director Asghar Farhadi takes his time unraveling this French (with English subtitles) soap opera, maintaining a faintly chilling suspense as he does. Emotions, repressed or not, are high. We worry what the combustible little Fouad will do (he’s messing with knives, having tantrums on the Metro, the works), how Lucie’s teen angst will express itself.

Mosaffa is very good at taking on the role of "the adult" here. Rahim underplays a sort of quiet, guilty resentment to perfection, and Bejo makes Marie seem perfectly reasonable -- until that instant she isn’t.

The surprises in "The Past" don’t justify its length. But Farhadi has created a believable, lived-in world of cluttered kitchens, cramped small businesses and the little people with big problems who inhabit them. Like the characters in this inter-connected Paris-Iranian subculture, you may feel the need to let go of "The Past," only to realize, after the credits, the hold it still has on you.

Rated PG-13 for mature thematic material and brief strong language.