Young ladies, what did your mother warn you about foreign travel?

Sure, it starts with seeing the sights, taking the photos, flirting with the nice foreign fellow. That’s followed by the make-out sessions in the clubs, the sex in the shower.

But just you wait. It’ll all end in shackles and padlocks, walled into an abandoned apartment building, imprisoned by a pervert.

“Berlin Syndrome” takes torture porn back to the place where sado-masochism was invented. It’s a slow-moving/unsatisfying in the end how-will-she-escape thriller dragged out by too many scenes explaining the torturer’s psyche, undone by an ending that no Hollywood studio would allow past the “bad idea in the script” stage.

Teresa Palmer (“Hacksaw Ridge”) is Claire, a young Aussie photographer in Berlin on assignment. Or so she says.

“People who travel alone are usually in search of something.”

That’s the street-corner come-on of Andy, a high school English teacher played by Max Riemelt (“Warsaw ’44”). Andy is charming, engaging; something of a gentleman, or so Claire thinks.

One hundred years of German villains in the cinema isn’t enough for her to spot the “sinister” in his eyes. Germans always make the best bad guys.

She falls for him, right up to the moment she realizes he’s locked her in while he goes to work.

“Yeah, and I’m going to tie you up when I leave tomorrow!”

Oh, you tease!

The alarm bells ring in her head, and as much as she pretends this is “normal,” we know she’s just trying to lull him into making a mistake. She knows she’s in peril. In an instant.

Cate Shortland’s thriller, based on a Melanie Joosten novel, squanders good lead performances and a simple, primal set-up as it changes points of view, letting us see how Andy spends his days — his efforts to appear “normal,” to cover his tracks. School, chats with his father, a party, all give hints to his psychosis and its origins.

Because every minute we’re not trapped in that abandoned apartment building with Palmer’s Claire is wasted. The lady proved in “Lights Out” that she can carry a thriller, create empathy and make us reason her way out of this with her.

Shortland does nothing of the sort. “Berlin Syndrome” may get across Claire’s shock, victim’s guilt and fear of her captor, but it never lets Claire make the most of her escape possibilities and cheats a bit when she finally decides on one.

It’s not bad, nor is the under-rated/under-used Palmer.  But “Berlin Syndrome” gets in its own way, fails to tease out the false hopes and generally leaves one wishing for a shorter, tighter and more viscerally satisfying version of this same, creepy story, about the sort of terrors and kinds of men mothers warn their foreign-traveling daughters about.

MPAA Rating: R for disturbing violent content, strong sexuality, nudity and some language

Cast: Teresa Palmer, Max Riemelt

Credits: Directed by Cate Shortland, script by Shaun based on the Melanie Joosten novel. A Vertical release.

Running time: 1:54