The set-up has “can’t miss” built into it.

A “posh,” educated and upper class family’s son falls for a brassy, sexy and gauche exercise instructor. His buttoned-down, everything-just-so Mom finds herself forced to deal with unsophisticated and less-than-hygienic potential in-laws as the foul-mouthed bride-to-be palms off planning the wedding, in her family’s backward home village, onto uptight Lucia.

But dios mio, how “The Perfect Family” manages to barely wring a single laugh out of this would fill a “How NOT to Make a Screen Comedy” textbook.

Let’s start with the most obvious. Lucia, played by Belén Rueda (“The Orphanage,” “Sara’s Notebook”), is scripted into making the least interesting journey over the blandest character arc you can imagine.

The film’s first scene has her son (Gonzalo Ramos) nervously rehearsing how he’s going to break the news to a demanding “perfectionist” woman who will never approve of the slovenly, tattooed tart he’s taken up with.

And what does Lucia do when she gets this news? Nothing. She holds her tongue as Sara (Carolina Yuste) gives her half a dozen clues that this isn’t an appropriate match, and lets Sara steamroll her into doing all the wedding planning for them.

She maintains good manners in the face of Sara’s bus driver Mom’s (Pepa Aniorte), crude and coarse manners and Sara’s dad’s Miguel (Jose Coronado) increasingly inappropriate attentions, something her older, distracted-astronomer husband Ernesto (Gonzalo de Castro) wouldn’t notice, even if he went along on the scouting trip to wintry Soria, the ancestral home of Sara’s family.

You think, “Well, she’s figuring out a way to sabotage this wedding” encouraging opinionated free spirit Sara to announce her disinterest in the Catholic church to the priest (Jesús Vidal), whom Lucia hopes would see that as a deal breaker.

Nope. That whole train of comedy never leaves the station.

All sorts of possibilities pop up for pulling the seemingly mismatched but under-scripted couple apart. But director Arantxa Echevarría and screenwriter Olatz Arroyo aren’t interested in the youngsters, either in the classic rom-com “obstacle” of mom who wants to break them up or in the least. We don’t see or feel what “connects” them, save for a “she’s so free” endorsement from son Pablo, and hearing their noisy sex in the next room.

What the filmmakers pursue instead are Miguel’s lecherous, boundaries-ignoring come-ons to the mother of the man his daughter expects to marry. He’s in love!

I guess that’s funny in principle, sort of the ultimate transgression. But the execution of that twist, for laughs, is as funny as a funeral. Rueda is supposed to journey from prissy and resistant to intrigued and tempted, and nothing in her performance makes that click. As played by Coronado and written by Arroyo, Miguel is more relentless than charming.

How an educated, refined woman sees anything to succumb to about this creep is beyond me. He’s leaning in, touching hands in front of the priest in the middle of the wedding ceremony.

Note to director Echevarria — a SLAP would get a laugh and be wholly logical in that moment. The audience, at least the one on this side of the Atlantic, is almost begging for it. The possibilities following a public slap in the middle of a couple exchanging vows are chaotic and rich. The repercussions of what happens instead are like everything else about “The Perfect Family” — dull, disastrously imperfect.

Whatever comic possibilities the picture had with its initial set-up, it devolves into an even LESS funny “It’s My Turn” tale of Lucia’s personal growth. So this woman her son was afraid of disappointing is such a lifelong pushover that her “everything must be perfect” life was achieved, how exactly?

Making your leading lady passive when she’s supposedly “My way or the highway” and giving your leading character so little agency undercuts the entire premise of the movie and what’s supposed to be comic about it. Lucia’s so controlling she runs everything about Ernesto’s life, even tying the absent-minded professor’s ties for him. And she’s just letting all this stuff go wrong around her without saying a word?

The dialogue (in Spanish or dubbed into English) is tortilla flat, with only Sara’s unfiltered sweat-suited dolt of a brother (Lalo Tenorio) having anything funny to say or to play.

We treated to a few noisy big family argument moments, a bus driver snaps in traffic gag and sad “get everyone back together and headed towards normal” Christmas dinner, all of which land with a thud.

“The Perfect Family” is so tone-deaf and wrong-footed that you’d feel annoyed at the filmmakers, if you weren’t already busy pitying them.

Rating: TV-MA, sexual situations, profanity

Cast: Belén Rueda, Jose Coronado, Gonzalo de Castro, Pepa Aniorte, Carolina Yuste, Gonzalo Ramos, Lalo Tenorio and Jesús Vidal

Credits: Directed by Arantxa Echevarría, scripted by Olatz Arroyo. A Netflix release.

Running time: 1:46