“In Secret” is a thumping good melodrama, a style of storytelling that’s fallen into obscurity. It generally depends on themes of sexual repression, which hasn’t been much of an issue since great-great-grandmama’s day. Lately if you discover your lover’s been cheating, you don’t administer or take strychnine, you unfriend them on Facebook. The good news is there’s less business at the morgue. The bad news is we’ve lost a terrific source of oh-no-she-didn’t story lines.

Adapted from Emile Zola’s “Thérèse Raquin,” this is a story of lust, madness and destruction set in the dingy back streets of 1860s Paris. Call it petticoat noir. Thérèse, played to scheming perfection by Elizabeth Olsen, is a stifled, simmeringly unhappy beauty married off according to her aunt’s wishes to her sickly cousin Camille. Though Olsen looks très jolie in period undergarments, her spouse lies there like a lox. Kudos to “Harry Potter’s” Tom Felton for making that credible.

Trapped in a sexless union and the petit-bourgeois clique of her shopkeeper aunt’s banal acquaintances (Thursday is dominoes night!), Thérèse is an emotional time bomb. Her eyes positively pulse with resentment. When naive Camille brings home his diabolically handsome friend Laurent (Oscar Isaac, exquisitely untrustworthy), passions erupt that goad them to deceit and murder.

In addition to sordid doings and clear-cut characters, Zola provided a solid three-act structure, with each chapter leading to a climax — murder, marriage, suicide. The film has a wonderful sense of physical and moral dankness. The cinematography is colorful and airy when the story opens in the countryside, then grows suffocating in gay Paris.

Director Charlie Stratton portrays the capital’s lower depths as a hive of shady bistros and leprous souls, claustrophobic and sinister. The Seine looks sewage-brown. Images of murky fluids recur throughout the story, echoing the gothic-tragic drowning that kills the obstacle between Thérèse and Laurent. It also triggers the anxiety that kills their ardor and sends them spiraling into degradation. They never repent of their acts. Their suffering is not moral anguish but nervous apprehension inflamed by absinthe.

The acting here is not in the current line of naturalistic realism. That would hardly suit the lurid subject matter. Olsen and Isaac and Fenton and Jessica Lange as Mme. Raquin perform in a state of ecstatic make-believe. The doomed, damned lovers positively revel in their debasement. Lange’s character is rendered mute and paralyzed by a grief-induced stroke. She spends the last act trying to communicate the killers’ guilt to her doting circle of friends with fierce looks. Their work is delicious ham — ham baked in honey, studded with cloves, and sliced thick.