The couple that kills Nazis together, stays together.

Or so the heroes in Robert Zemeckis’ new World War II film, “Allied,” thought. Brad Pitt and Marion Cotillard star in this throwback vehicle, one with a major reveal that’s spelled out in ALL CAPS in the trailer.

It’s got romance! Action! Mystery! And more than a few manufactured moments to gin up our intrigue. It’s all handled masterly by Zemeckis, aided by stars dabbling in old school chemistry.

(Final warning: The trailer below reveals the story’s big twist)

Pitt stars as Max, an intelligence officer prepping for a dangerous assignment in French Morocco. He must play house with Marianne (Cotillard), a French spy infiltrating the Nazi high culture.

Together, they’ll attempt to take out a German official while pretending to be hopelessly in love. She’s a quick study on feigning romance. She knows everyone is watching all of the time, and the wrong move can blow their cover.

If that means stealing a steamy kiss on a rooftop … well, it’s all in a day’s work.

Two guesses where the story goes next? What you may not see coming is the aforementioned twist, one that tests the duo’s loyalties and makes for a bracing third act.

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Pitt so often underplays his marquee good looks it’s surreal to see him embrace them. No scruff, haggard haircuts or hokey accents. Only you can tell he’s doing just that. A major movie star, think a Gable or Grant, would effortlessly deploy his charm offensive.

Not Pitt.

You can sense him thinking, “I’m an A-lister and I gotta show it.” It’s not a bad performance. It’s simply one where you can occasionally see the strings being yanked.

FAST FACT: Marion Cotillard’s Best Actress win for 2011’s “La Vie en Rose” made her the first French actress to win the award since 1960. (Simone Signoret won for “Room at the Top”)

Cotillard, by comparison, is flawless. She’s credible when the two are pressing each other in ways that could save their lives. Better still, she’s believable as a cynical spy giving in to her emotions.

The trailer suggests an action-packed adventure. “Allied” is far more sedate, even when the core mystery tightens around our heroes. That leaves us hungry for the smaller tells, and Zemeckis and crew deliver. Watch Marianne as she unbuttons her blouse to test Max’s game face.

Or see the two flex their skills with a weapon, a sequence brimming with sexual tension. Pitt and Cotillard have that elusive chemistry, and it makes the couple’s fate all the more consequential.

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Screenwriter Steven Knight (“Burnt”) delivers a pair of original characters, their fates partially sealed by the military brass surrounding them. Knight fumbles while trying to goose the big mystery. Suddenly, cliched characters enter the frame for only one purpose. That brazen approach only distracts from the emotional finale.

HiT or Miss: “Allied” is the kind of movies Hollywood used to make without apology. It’s a sophisticated thriller buoyed by stars who understand it’s their time to flash movie star glamour.