Some of its power to shock and repel still clings to “Hardcore,” the debut feature by “Taxi Driver” writer turned writer-director Paul Schrader.

But as it travels from the conservative Rust Belt just before Reagan and the “Rust” set in, into the strip clubs, sex shops, lap dance “arcades” and porn film industry of the Southern California of 1979, it can feel almost quaint as it exposes a mostly-naive Middle America to variations of “The World’s Oldest Profession.”

It’s a quest thriller, loosely based on the classic John Wayne/John Ford Western “The Searchers,” about a Grand Rapids, Michigan father hunting for a teen daughter when went missing on a trip to church camp in California, and somehow wound up in the sordid, dangerous porn film/sex-worker underworld of Van Nuys and environs, a landscape later surveyed in Paul Thomas Anderson’s epic “Boogie Nights.”

George C. Scott gives us shades of guilt-ridden concern, shock and his trademark enraged histrionics as Jake VanDorn, owner of his family’s venerated furniture manufacturing concern. We’re immersed in their world, first, a snowy Christmas with the whole clan gathered, singing carols, dutifully attending their Dutch Reformed (Calvinist) Church and enjoying the bountiful fruits of lives their belief system tells them they were predestined to receive.

Writer-director Schrader’s religion has long informed his cinema, something he made even more obvious with his 2017 “comeback” movie, “First Reformed.”

When Jake says grace before the whole family that evening, he finishes with “keep up safe from harm and danger, if it be thy will.” Remember that.

In “Hardcore,” that faith is discussed and those values are tested when Jake gets a call that his daughter disappeared on a field trip from California church camp to the Knotts Berry Farm theme park. His support system is such that his brother-in-law (Dick Sargent of “Bewitched”) thinks nothing of saying he’ll book the flights and go with him out West to find Kristen (Ilah Davis) or at least get some answers.

Sitting with a not-particularly comforting cop (Larry Block), seeing a wall of teen girls and boys “missing persons” posters and fliers around him makes Jake despair. But on the cop’s recommendation, he hires “the best” private investigator for this sort of case in that corner of Southern California.

Peter Boyle has one of his best roles and runs with it as Andy Mast, a sleazy guy in a sleazy business doing a sleazy job of hunting through a world of sleaze. Mast’s bluntly sexual questions about the missing teen and his salty language offend VanDorn.

“You wanna hire a choir boy, go back to Grand Rapids.” But he assures Jake he’ll find her in “a week or two, a month at the most.” He doesn’t.

But as seasons change Mast shows up in Grand Rapids, takes Jake to a seedy 8mm peep show porn theater where he shows what he did find. Kristen is working in “Hardcore” porn.

That and rising impatience with how long this is taking launches Jake’s odyssey, a conservative man in conservative suits wandering the mean and sordid streets, showing pictures of his daughter in that dirty movie to sex workers and porn shop operators (Tracey Walter plays one, naturally), roughing up Mast in his righteous wrath over his child’s fate and the private eye’s “methods,” which include bedding porn actresses on VanDorn’s dime “for information.”

Eventually, our hero will have to descend to everyone else’s level, pose as an “investor” with a porn producer (Leonard Gaines, in a definitive portrayal of a “type”) in order to trace his child’s journey, determine her fate and perhaps accept his role in it.

“The Searchers” connection comes from VanDorn’s guilt about something that happened when he wasn’t there to protect his child and his worry about his role in her “predestination.” Boyle’s Mast underscores it by referring to the Midwesterner as “pilgrim,” more than once.

VanDorn’s tour guide to this underworld becomes the skinny, struggling actress/sex-worker Nikki, played with a brazen, somewhat dim worldliness by Season Hubley, in what would be her biggest role. Through her, VanDorn makes his way through connections, from San Diego to San Francisco. Through her, the audience learns a little about Calvinism as practiced by the Dutch, the “TULIP” doctrine, for instance.

His brother-in-law insists “You have to have faith,” but VanDorn slowly grasps the futility of magical thinking. “Would you?” under the same circumstances. “Could you?”

Some of the lore attached to the film is how first-time director Schrader enraged the imperious, Oscar-winning Scott so much that he made Schrader promise to “never direct again” before he’d agree to come out of his trailer. As the story is told by Schrader, we can take that with a grain of salt.

But 20 years before “Boogie Nights,” the famed degree of difficulty this production encounted is borne out by scene after scene of porn world habitués telling Mast, and then VanDorn “I don’t know nobody” else in this industry. We’re told of the box office hits of the era like “High School Honeys” and “Little Oral Annie.” Porn was just becoming legal in much of the country, and the filmmakers met exactly that sort of stone-walling everywhere they tried to film.

By the late ’90s, porn had transitioned to home video and plunged into websites and live streaming and its “history” was out there for all to see and Paul Thomas Anderson to explore with more ease and swagger. Anderson was able to get a lot of famous faces for his cast. Schrader had to settle for Scott, Sargent and Boyle, with the less known Hubley and a lot of unknowns such as a very young Ed Begley Jr., who turns up as a most professional porn actor in a police uniform.

“Quaint” or not, “Hardcore” has an authenticity about it that keeps the viewer engaged, even as we lose hope that it will ever wholly address the themes Schrader introduces but never truly gets his hands on.

Scott’s performance has grace notes, and a moment or two of classic Scott over-acting. But watch his tussle with a porn insider in the third act, the two of them tearing through “sets” in the pasteboard walls of a San Francisco S&M parlor, tumbling over each other in the street as they tangle.

That’s no stunt man. That’s 40something Oscar winner George C. Scott, committing to a part and taking the “shame” of the subject matter and the bumps, bruises and scrapes required, once he finally decided to leave his trailer.

Rating: R, violence, sex, nudity, profanity

Cast: George C. Scott, Peter Boyle, Season Hubley, Leonard Gaines and Dick Sargeant.

Credits: Scripted and directed by Paul Schrader. A Columbia release on Tubi, Amazon, et al.

Running time: 1:48