The opening act of “Wolf Pack” is disorienting, bracing and action-packed enough to give one hope we’re heading into a solid action thriller/mystery.

Then somebody tosses sand into the gears and this B-movie grinds to a halt in the middle acts. Soap operatic “backstory” is added. The plot gets deeper into “pipelines” and China’s interest in them than anyone would care to know.

But it’s at moments like this that many a failing thriller serves up a line that sums up how badly things have gone wrong.

“Evacuate the building!” a Central Asian energy minister barks, in English (the film is in Mandarin, with subtitles, and has some English dialogue).

“Sir, let’s MOVE,” an aide/bodyguard snaps back.

“NO,” says the guy who JUST SAID “Evacuate” replies, perhaps confused. “We must stay here!”

That’s kind of how things go in the movie writer Michael Chiang (“Army Daze,””Our Sister Mambo”) makes his writing and directing debut.

Ke Tong (Aarif Rahman, a physics student turned Hong Kong pop star turned actor) is a doctor in an impoverished desert crisis zone when we meet him, cynical enough to suggest of a dying patient, “Better put him out of his misery.”

That kind of goes against the grain of the idealistic image this charitable, handsome young man of medicine has projected in magazine profiles. But he’s off before we have a chance to wonder if he’d pass muster with Doctors Without Borders.

On the bus to the air strip he’s recruited by an eager young blonde (Luxia Jiang) who wants his help rescuing kids trapped in a volcano in Java. Next thing Ke Tong knows, he’s spirited off the bus, strapped to the woman who just tossed his luggage, passport, etc into a river and air-grabbed by a passing helicopter. He figures out he’s being kidnapped a minute or three before he’s drugged.

Ke Tong hits the ground as a reluctant member of this team of contractors who operate under a corporate name borrowed from Chinese military history — Bei Wei. When they’re quickly captured, Ke Tong, nicknamed “Handsome” by the others, is forced to operate on some Central Asian warloard’s wounded brother.

That ends in a firefight. Who ARE they guys and this woman? Who is paying them and what is their agenda? Because this “mission” isn’t over.

But the deeper we get into it, the more we learn the backstories of those mercenaries — played by Jin Zhang, Luxia Jiang, Mark Luu, Liu Ye, Yi Zhang and Kuo-Chung Tang — and “Handsome,” the less interesting “Wolf Pack” becomes.

“Wolf Pack” works best when we’re as wrong-footed as our hero, when he’s trying to escape this mysterious gang’s clutches, desperate for “Who do you WORK for?” answers.

“I’m not a mercenary. I’m a DOCTOR!”

The whole medical thing is dropped very early on as we learn more about this doc, who has survival and evading pursuers and fighting skills his captors don’t know about.

Well, the head guy Diao (Jin Zhang) does.

The effects are generally adequate even if we can tell digital fire or RPG explosions have been added. The multi-lingual dialogue is a bit of a chore to act in — for some — and listen to (English pronunciations take a beating) for everyone else.

And the best martial arts action and gunplay are in the first act. After that, this convoluted “Wolf Pack” tale turns into something of a mutt.

Rating: unrated, violence

Cast: Aarif Rahman, Jin Zhang, Luxia Jiang, Mark Luu, Liu Ye, Yi Zhang and Kuo-Chung Tang

Credits: Scripted and directed by Michael Chiang. A Well Go USA release.

Running time: 1:44