Of all the promising places “Frank & Penelope” hints at or threatens to take us, how’d they end up at a murderous “sin eater” cult at a combo tow truck service, garage and motel — complete with a tunnel and body disposal pit in the desert southwest?

Veteran character actor turned writer-director Sean Patrick Flanery (now on TV’s “The Boys”) references “Thelma & Louise” directly, “Something Wild” and “Dirty Mary, Crazy Larry” and the like indirectly in this sexualized, infuriatingly-talky and slow genre thriller.

Frank (Billy Budinich) quits his job and catches his wife sexing up another man in their house. That’s how he ends up, dazed, in the alley behind that strip club. That’s how he meets a pole dancer (Caylee Cowan, channeling Melanie Griffith). Where ya’headed?

“Away.”

Me too, once, she says.

But “away’ just don’t show up on Google maps.”

You need to meet “Penelope,” she purrs. And thus another soon-to-be-satisfied customer is lured in, $25 drinks and private dance to follow. Frank is smitten. Penelope, “an act” she puts on, she implies — is good.

But he interrupts her and her boss/”boyfriend” (Flanery) as they’re brawling over her getting-too-friendly with a customer, and how much they’re going to steal off Frank’s credit card.

The scarlet woman this meets her first-ever knight in shining strip club armor.

“If a man don’t fly into a rage, he ain’t in love.

Trade the Prius for a ’68 Super Bee, and they’re off. They’re headed for the “the prettiest road in America,” Frank says, the one from “the last scene in ‘Thelma & Louise.'” Has Penelope ever seen the movie? She’s smitten, or damned good at acting like it.

“I gotta freight train’a love, headed only for him.”

Flanery’s script traffics in truck stop philosophy, con artist speeches and horror movie tropes that long ago turned into cliches.

I swear, there are just four run-down desert motels that turn up in every one of the hundreds of thrillers like thus.

Johnathan Schaech (“That Thing You Do”) plays the latest in a long line of “Appalachian sin eaters,” a white-haired cult king, keeping a handful of minions in line by means hypnotic or even supernatural. He’s going to interrupt Frank & Penelope’s odyssey. Permanently?

Kevin Dillon plays a flirtatious, drawling Texas sheriff who wears jeans on the job.

And horror icon Lin Shaye has a cameo as another “short term” guest in that motel, where patrons check in but don’t check out.

Flanery scripted this, and the big laugh in that is that somebody else had the cheek to claim a “story by” credit for this cut-and-paste-from-other-movies nonsense.

A framing device — we’re learning about the romance of Frank & Penelope through his “journal,” read/narrated by Frank’s nurse (Sonya Eddy). He’s in a coma. That conceit is mercifully abandoned once Flanery realized — belatedly — that it’s rubbish.

Cowan (“Sunrise in Heaven”) is the big find here, giving us a doll-voiced minx with a hardened sex-worker’s shtick and a survivor’s instincts. Penelope works her search for “something that makes my thighs twitch” act on every heterosexual male in range, and turns most into putty.

If only this script had found some place interesting to send her and Frank. If only the ending didn’t scream “We’re outta money/time/etc.” If only this crawling, drawling horror saga had gotten to the damned point and made something out of it.

Rating: R for strong violent content, sexual content, brief nudity, language throughout, sexual assault and some drug use.

Cast: Caylee Cowan, Billy Budinich, Johnathan Schaech, Sean Patrick Flannery, Donna D’Errico, Sonya Eddy, Lin Shaye and Kevin Dillon

Credits: Scripted and directed by Sean Patrick Flanery. A Redbud release.

Running time: 1:53