Among the many virtues of “Duplicity” is its title, which could hardly be more apt. Everything in Tony Gilroy’s smart new film should be taken with the proverbial grain of salt.

The movie is part romantic comedy, part heist story, part corporate espionage. You’re apt to be a bit confused when the dust settles, but you will have been thoroughly entertained.

Claire Stenwick (Julia Roberts) and Ray Koval (Clive Owen) are former American and British secret agents. They have found new careers as corporate spies for a company called Equikrom in its battle against archrival Burkett & Randall for supremacy in the fiercely competitive personal-hygiene products industry.

Stenwick and Koval also are lovers — though, as former spies, they’re challenged in the mutual trust department.

Tom Wilkinson plays Howard Tully, the CEO of Burkett & Randall. Paul Giamatti portrays Richard Garsik, Tully’s hot-headed counterpart at Equikrom.

Their clumsy fisticuffs on an airport runway provide the movie’s only real violence, though the dustup is played for laughs during the opening credits. “Duplicity” also is free of car chases, gunfire and other forms of mayhem. Here, the principal weapons are words, high-tech snooping devices and double agents. Lots of double agents.

Making extensive use of flashbacks, Gilroy spends much of the movie setting up the corporate war and the curious relationship between Stenwick and Koval. The story slams into high gear when Equikrom learns that B&R is about to unveil a product so wondrous that it will conquer the market and crush Equikrom in the process. Garsik immediately orders his spies to swipe the formula. Stenwick and Koval comply, but their real aim is to steal it for themselves, sell it for millions and retire to a life of lovemaking and champagne.

“Duplicity” benefits mightily from the chemistry between its romantic leads and from the performances not only of Roberts and Owen, but of Wilkinson and especially Giamatti. Writer-director Gilroy sets a brisk pace and keeps the dialogue crisp and witty. The movie’s surprise ending is clever but somehow feeble in execution, and some will find the plot exasperatingly tough to follow.

But in the end, it doesn’t matter; flaws are trumped by fun. My advice is to suspect everything you see and hear, enjoy the ride and trust that in the end it will all be clear.

OK . . . clear enough.