Is it okay to laugh? That’s what audiences are likely to ask about the histrionic staging of Helen Edmundson’s new adaptation of Emile Zola’s 1867 novel, “Therese Raquin,” which stars Keira Knightley as the bored young wife who has a tempestuous affair with the best friend of her spoiled Mama’s boy of a husband. But although Evan Cabnet’s hammy direction of the first act does elicit uncomfortable laughter, the physical production is exquisite, and by the end of the act the performers have found the raw passion to leave the audience gasping.

Gabriel Ebert, who won a Tony for his music-hall turn as Mr. Wormwood in “Matilda,” brings the same goofy sensibility to Camille Raquin, the sickly only child and heir of the doting Madame Raquin (Judith Light, regal but with attitude). The man is such a pampered baby (“You are delicate, you will always be delicate,” his mother croons), he’s oblivious to the charms of his cousin and bride, Therese, played by Knightley with all her grace and beauty well hidden under a barrel.

But even for such a bona-fide fool as Camille (“My funny little cousin,” he calls his bride), the characterization is much too light-hearted (and empty-headed) for this Grand Guignol tale of murderous lust and obsession.

Like a kindergarten teacher who has spent too much time romping with the kiddies, Knightley is infected with the same stupid-bug. Tasked to play a delicate and sensitive woman smothered under the confinements of self-satisfied middle-class respectability, she slouches around her mother-in-law’s bourgeois flat looking petulant and behaving rudely in front of visitors. And when Camille brings home his friend Laurent (Matt Ryan, who looks smashing in Jane Greenwood’s form-fitting period garb), she gawks at this conceited stud with the open-mouthed adoration of a lovesick adolescent.

Knightley hangs onto Therese’s girlish demeanor until Laurent puts her out of her misery by seducing her — at which point, Knightley comes alive and delivers Zola’s lushly romantic sentiments with the exuberant joy of a woman famished for love and ripe for a lusty affair.

“There is blood in my veins,” she cries. “I thought they had bled me dry. Drained me. Flattened me until I was a pressed flower.” Beowulf Boritt’s astonishing set — a massive horizontal structure of dark woods and gloomy furnishings that swoops down from the flies like a raptor — visually conveys that ominous feeling of being buried alive.

That’s fun for a while, and both Knightley and Ryan throw themselves into the flames of the lovers’ fevered passion. But the play really catches fire when Laurent, grasping the danger of their affair, speaks his secret wish out loud. “My God, I wish we could be rid of him!” — and then passes that responsibility on to Therese. “Couldn’t you get rid of him?”

Getting rid of the buffoonish Camille brings out the best in everyone. Keith Parham’s limpid lighting design casts a watery vapor over an abstract antechamber of the otherwise naturalistic set. Josh Schmidt’s operatic music heightens the dramatic mood until our nerves are ready to snap. And voila! The scene is set for the psychological breakdown of the guilty lovers in the second act.

Knightley and Ryan are ravishing — and articulate — as these fierce bourgeois Macbeths, undone by their own greed and passion. But Judith Light also holds the stage after Madame Raquin has a stroke, unable to speak, but communicating with eloquence with her eyes.

The play ends as it must, in tragedy. But how we do love their misery.

Broadway Review: ‘Therese Raquin’ Starring Keira Knightley

Studio 54; 1,006 seats; $137 top. Opened October 29, 2015. Reviewed Oct. 23. Running time: <strong>TWO HOURS, 30 MIN.</strong>

  • Production: A Roundabout Theater Company production of a play in two acts by Helen Edmundson, based on the novel by Emile Zola.
  • Crew: Directed by Evan Cabnet. Sets, Beowulf Boritt; costumes, Jane Greenwood; lighting, Keith Parham; sound & original music, Josh Schmidt; hair & wigs, Tom Watson; fight director, J. David Brimmer; dialect coach, Kate Wilson; production stage manager, Peter Hanson.
  • Cast: Keira Knightley, Gabriel Ebert, Matt Ryan, Judith Light.