This isn't saying much considering what a dubious season it has been, but "Salt" is just about as accomplished in the action department as any film released so far this summer. It's a pure exercise rather than a fully developed narrative, but director Phillip Noyce (1999's "The Bone Collector") and screenwriter Kurt Wimmer (2009's "Law Abiding Citizen") keep things moving with tight pacing, competent stunts, well-choreographed death-defying moments, and a plot that gets to the point and then leaves the viewer guessing for the duration. Because the characters are pawns within a chess game rather than distinctly three-dimensional personalities, and because interest hinges so heavily on not yet knowing their intentions the first time around, the picture will likely not have much replay value. Nevertheless, the initial experience is preposterously fun, free of the heavy exposition and bloated clunkiness of Christopher Nolan's recent non-dreamlike farce of the subconscious "Inception."

CIA officer Evelyn Salt's (Angelina Jolie) plans for a romantic evening celebrating her wedding anniversary to husband Mike (August Diehl) are shattered the moment Russian defector Orlov (Daniel Olbrychski) fingers her as a top-secret spy planning to assassinate the Russian president while he attends the U.S. vice president's funeral in New York City. Evelyn is adamant that she's being set up and, with the help of some sneaky maneuvering, goes on the run from colleagues Winter (Liev Schreiber) and Peabody (Chiwetel Ejiofor). Even as Evelyn touts her innocence, she mysteriously moves ever closer to Manhattan—only the first stop in Orlov's plan of terror to take down the country.

No motion picture named "Salt" should pass by without the story-thickening introduction of a nemesis named Pepper, but the opportunity is a missed one (so is, for that matter, the use of Salt-N-Pepa's "Push It" on the soundtrack). Indeed, the film hasn't much of a sense of humor at all—a shame, since the whole thing is rather silly once all the puzzle pieces come together and Evelyn's true motives are revealed. Taken on its own respective terms, though, the picture works. Suspending one's disbelief is a must, especially as Evelyn jumps from the top of one tractor-trailer to the next across a bustling highway in a bid to escape authorities, crashes a car off a bridge and walks away unscathed, leaps from a moving subway train, and infiltrates two highly-guarded political functions. Director Phillip Noyce, aided in no small part by the committed, physically intense performance of Angelina Jolie (2008's "Wanted"), accepts these plausibility leaps and, thus, help the audience buy into them as well. It doesn't hurt that the viewer is too busy, anyway, trying to figure out what side of the fence Evelyn is playing on. Is she truly not guilty, is she a conniving Russian villainess, or is she something in between? Seeing how the question marks are answered is a big reason why it's so diverting.

Regardless of whether Evelyn Salt is "good" or "bad," she certainly isn't morally clean, risking (and losing) the lives of loved ones, committing fraud and theft at every turn, and forced to deceive a great many people in the name of pulling off her scheme. She's got a conscience, no doubt—a small bit where she must give away her pet dog quietly suggests her instantaneous loss of identity—but is she someone worth caring about? Angelina Jolie renders the query moot, embodying a fascinatingly enigmatic character whose flaws and mistruths are part of her make-up. No matter what she's doing, the actress ensures that it seem real. With so much of the production centering on her, the supporting cast are able, but have little to do. As friend, coworker, and sudden adversary Winter, Liev Schreiber (2010's "Repo Men") is typically reliable, holding the screen when Jolie is off of it.

"Who is Salt?" the tagline for "Salt" reads. By the end, you'll have a concrete enough answer to confirm that a sequel—of which there is a setup for one—probably wouldn't be the best idea. The novelty of the film is in wondering all along if Evelyn means well, or if she is a ruthless spy and assassin. Without this mystery, the appeal would wilt and a continuation would have no choice but to become more generic, a cross between James Bond and—shudder—2002's "Ballistic: Ecks vs. Sever." As a standalone feature, however, "Salt" is fitfully rousing and intriguingly evasive, crafty if not particularly deep. Like its agile title character, it keeps on truckin'.