It’s a reflex reaction.

You see an actress “putting it all out there” for a role — skin, simulated sex, violence and drug abuse. You remember how Hollywood burns through starlets, uses and misuses young actresses until many are “used up,” most often long before having a shot at becoming a Leading Lady.

And you think of the film’s premiere or that first time that young woman’s parents see the film and fret over what they must think of her choices, this often unsavory, reflexively sexist “business” that their precious child has gotten into.

Then you see a movie like “Strange Darling,” with Willa Fitzgerald talking the kinky talk and sprinting, bloodied, out of a motel room into the broad light of day in nothing more than her unmentionables, and you have to say, as a parent or in words of reassurance to the parents — “That’s a gamble that was totally worth it.”

Most of Fitzgerald’s “breaks” up to now have been on episodic TV — “Scream: The Series,” “Reacher,””The Fall of the House of Usher.” I remember the name from if not her supporting performance from “The Goldfinch” and “Desperation Road,” a recent Mel Gibson thriller which, as everyone knows, isn’t going to warrant a gold star on any resume.

If she’s going to make it happen, a big showy part in an edgy, nervy thriller like “Strange Darling” is a safer bet than it looks.

It’s an “unsafe sex” play thriller about a hook-up gone wrong, a motel encounter involving choking, handcuffs, “safe words” and worse. And writer-director JT Mollner, telling this “true” story in “six chapters,” shown out of order, is all about twists, the dark and darker turns, the shocking violence and the upended expectations.

Kyle Gallner of “Smile” is the unnamed hook-up, a stereotype with the mustache, pick-em-up truck with beer in the back and a gun under the seat.

“The Lady” seems to figure he fits the profile, and not just a voting “weirdo” one.

“Are you a serial killer?”

Pretty, sexy in a magenta wig, boots and prone to a lot of eye contact, she’s well-read on “the kind of risks a woman like me takes to have a little fun.”

Recreational sex with a stranger is on both their minds. But she’s out to lay down her concerns and set up some ground rules.

As the film opens with her, in red scrubs and red boots, blonde hair mussed and weepy and running for her life, we can guess that somebody didn’t respect the “safe word.”

The “chapters” jump about as we meet a couple of “old hippies” (Barbara Hershey and Ed Begley Jr.) whose help she seeks, and learn how she came to be chased down a deserted Oregon road by a stereotype in a pick-up with her trapped in a “’78 Ford Pinto.”

“Seriously?”

Mollner is unsparing in the torture and violence and unblinking in the gender politics he puts in play. And Fitzgerald and Gallner just flat out bring it — the suspicions, the sketchy boundaries crossed, the role reversals, the blood that tells us things have gotten out of hand.

I didn’t love everything about this. Scenes have characters lose the logic of the moment and do the one stupid thing that would put them in the most jeopardy — repeatedly.

And a long opening title crawl tries to convince us this is a “true story” for some reason is READ in voice-over for the benefit of the reading-impaired (apparently) by Jason Patric.

But writer-director Mollner (“Outlaws & Angels”) doesn’t take many other missteps, and actor-turned-cinematographer Giovanni Ribisi (he has a cameo here) keeps his lens close even as he’s and his crew are sprinting ahead of the gasping Fitzgerald in hand-held chases.

It matters that the story’s told out of order. It’s great that they landed Hershey and Begley for small but chewy supporting roles. And Fitzgerald’s gamble on her most daring, naked (not quite literally) performance pays off in what could be her break-out role, even if she had a bit of explaining to do to mom and dad when the credits rolled.

Rating: R, graphic violence, drug abuse, sexual situations, profanity

Cast: Willa Fitzgerald, Kyle Gallner, Barbara Hershey and Ed Begley Jr.

Credits: Scripted and directed by JT Mollner. A Miramax release.

Running time: 1:36