Sydney Sweeney’s fans will come to the “The Housemaid” for the nudity and the explicit sex. Or so the cleavage-crammed advertising for this thriller would suggest the studio believes.

But they’ll stay for the violence, the twists, the climax and anti-climaxes spoiled by redundant voice-over-narration for dummies?

That said, I wouldn’t be shocked if this Paul Feig thriller — he did the scheming women “Simple Favor” pictures — touched a nerve and found an audience, any more than I wasn’t shocked at the sight of co-star Amanda Seyfriend acting circles around last year and this year’s “It” girl.

Sweeney, playing an unemployed young woman living in her car and desperate enough to endure a job that features humiliation and the threat of worse from the rich, privileged pricks who hired her, brings everything but “desperate” to her performance. Her bland wariness gives away the suspense this picture needs almost as much as a better title.

Letting actors/actresses read to the very end of the script isn’t always the best idea.

The job interview with Mrs. Winchester (Seyfried) makes it seem like a done deal. Nina even confesses to job prospect Millie that the one child she’d be expected to care for, along with cooking and cleaning and errands, will soon be joined by another. She hasn’t even told her husband, she confesses with widened eyes.

But hell, she hasn’t finished interviewing job prospects either. And when husband Andrew (Brandon Sklenar of TV’s “1923”) walks in, he’s surprised about the whole “live in” housemaid thing.

Something’s a little “off” in eager-to-confide Nina and “hot mess” doesn’t begin to do it justice.

Millie? She’s got secrets, and that appointment she isn’t allowed to miss tips us off. It’s with her probation officer.

The mystery unravels as a “Who’s playing with whom” tale, with testy Nina flipping out over perceived failings and hurling blame for everything that goes wrong at Millie, who — being “desperate” — just has to take these mind games and manipulations.

He’s awfully nice to her, but Millie should also be wary of the hunky, rich husband of the manor. If he’s seducing her in her dreams, that’s fair warning.

She opens up about her predicament in the voice-over narrated diary her probation officer insists she keep. No, not one line of that narration– which runs the length of the movie — is pithy enough to be quotable.

As the script (based on a Rebecca Sonnenshine novel) gropes around for suspense it stumbles through its assorted “surprise twists.” The whole second half of this long-film-that-plays-longer is so clumsily structured that it generally spoils the vengeful fun.

Seyfried takes up the challenge of pairing-up with Sweeney with a manic bravado that overwhelms Sweeney’s perpetual poker face. Elizabeth Perkins might have taken a few sips of battery acid between takes to dial up the cruel, imperious, judgmental mother-in-law whom nobody in the house, except for her son, can please.

Indiana Elle plays Cece, the little girl of the house who channels her granny as she holds “the help” to her seven year-old standards, even when it comes to morning orange juice.

“Juice is a privilege. Not something you drink out of a dirty glass.“

There’s promise to this or that character and in the twists that almsot certainly played better in the novel than Feig manages on screen. But the promise is squandered in a pokey, obvious movie that stumbles towards stupid in the anti-climactic latter acts.

As star vehicles go, “The Housemaid” doesn’t do Sweeney any more favors than the flops “Eden,” “Christy” or “Echo Valley” did. Two years into top billed stardom, and her best work is still the TV series (“Euphoria,” “White Lotus,” “The Handmaid’s Tale”) that first made her a famous sex symbol.

Rating: R, violence, explicit sex, nudity and profanity

Cast: Amanda Seyfried, Sydney Sweeney, Brandon Sklenar and Elizabeth Perkins

Credits: Directed by Paul Feig, scripted by Rebecca Sonnenshine, based on the novel by Freida McFadden. A Lionsgate release.

Running time: 2:11