Is it love or treason?

Few marriages survive the devastation of infidelity, but what if your spouse was cheating on the whole country? In the new film Allied, a Royal Air Force (RAF) officer suspects his wife could be spying for the Nazis. The story is neither an engaging romance nor a full-tilt thriller, but its meticulous details and artful twists make for a better-than-average movie.

Previously strangers, Canadian-born RAF wing commander Max Vatan (Brad Pitt) and French Resistance member Marianne Beauséjour (Marion Cotillard) team up in 1942 Casablanca for a risky assassination of the German ambassador. They pose in Morocco as a well-to-do married couple, a role in which Max demonstrates his discomfort. But Marianne says she knows what it takes to pull off a successful deception.

“I keep the emotions real. That’s why it works,” she tells Max.

Their feigned public displays of affection develop into private intimacies and seemingly genuine love. Max weds Marianne when they return to London, where they have a daughter, born outside during an air raid.

But Marianne’s stated key to effective spy craft haunts Max when British intelligence accuses his wife of working for the Germans. Investigators force Max to assist in a covert test of Marianne’s loyalties. If she is found to be a spy, protocol requires Max to execute her himself, or else he’ll be hanged for treason.

Allied (rated R for violence, some sexuality/nudity, language, and brief drug use) rolls forward at widely varying speeds. Scenes of Max and Marianne’s tranquil domestic life slam the brakes on the film’s early high-gear pace, but director Robert Zemeckis uses them to gradually rebuild the tension. Still, the film fixes on the fate of Max’s marriage and family, not on military consequences. (Viewers looking for a gritty, spellbinding tale of anti-Nazi espionage would do better to rent Max Manus or Flame and Citron—two superb, historically based foreign films.)

Zemeckis clearly means to invoke classic Hollywood cinema, but Humphrey Bogart and Ingrid Bergman never pawed each other in the back seat of a car. In fact, Allied’s two steamy scenes fail to season Max and Marianne’s bland romance. The problem is Pitt, who throughout the film is too wooden, even for a wooden character. Max could use a dash of Lt. Aldo Raine, Pitt’s screwball Nazi-scalper in Inglourious Basterds.

Set design often goes unappreciated, but here the film excels. Production designer Gary Freeman splendidly recreates Casablanca’s architecturally robust public squares and London’s cramped suburban neighborhoods. Allied overflows with era-authentic props: sputtering, single-engine fighter planes; late–1930s long-bonnet British coupes; shimmering, ankle-length evening gowns; bulky, dark-brown office desks; and lamp-strewn Parisian interiors.

The film’s finale won’t suit some viewers’ taste, but in its own way and under the wartime circumstances, it holds the family unit in high regard.