Grade: C-

The case of Anna Chapman and her cohorts, recently swapped for prisoners convicted in Russia of spying for America, might increase the credibility of this tale of a beautiful CIA operative accused of being a long-buried Soviet-era sleeper agent in the US. But “Salt” quickly sacrifices the slightest shred of plausibility in favor of mindless action, and becomes ever more preposterous as it rushes headlong to an apocalyptic finale. That wouldn’t be fatal if the movie took a tongue-in-cheek attitude to its absurdly convoluted story, but it’s played totally straight, and as a result is completely ridiculous—as wasn’t the case, for instance, with the “Bourne” movies to which this will inevitably be compared as a cross-gender cousin.

That’s despite the fact that Angelina Jolie, who plays Evelyn Salt, once again proves an adept action heroine, handling the physical demands of the part with aplomb and generating a genuine sense of mystery in the earlier reels. Unfortunately, even she can’t pull off a supposedly convincing switch to a male disguise later on, and by the end she seems to be impersonating a bad comic-book character.

Salt first appears being tortured in a North Korean jail, much as James Bond was at the beginning of “Die Another Day,” though the sight of Ms. Jolie writhing in agony, nude (and thus carefully positioned in the shot), is much more erotic. Released via the intervention of her admirer Mike Krause (August Diehl), an internationally famous arachnologist (!), she’s spirited back to America by her CIA boss Ted Winter (Liev Schreiber) and stationed in his DC office. She also marries Mike.

One day an elderly Russian named Orlov (Daniel Olbrychski) walks in and announces that a long-dormant Russian sleeper agent is being activated to assassinate the Russian president (Olek Krupa) in New York at the funeral of the deceased American vice president. And the agent’s name, he says, is Evelyn Salt. That information immediately makes her suspect to both Winter and counter-intelligence honcho Peabody (Chiwetel Ejiofor), but concerned for her husband, who’s suddenly gone missing and may have been kidnapped, Evelyn breaks out of the agency complex in the first is many big action set-pieces.

The rest of the first half of the movie is devoted to the feds chasing Salt through traffic as she makes a daring dash to freedom, only to find her husband gone. (The CIA and FBI guys in pursuit prove as mediocre as drivers and shooters as is usual in such cases.) And though the advertisements suggest that the big mystery at the heart of the script is whether Evelyn’s a Russian spy or not, the truth about that is revealed fairly early on.

It wouldn’t be fair to explain too much more about the plot, save that there is another big set-piece at the Big Apple cathedral where the vice-president is being memorialized. And the plot definitely thickens in the second half, winding up at the White House, where the American president (Hunt Block) becomes a pawn in an even more elaborate international plot. It’s here that scripter Kurt Wimmer launches a final surprise, unmasking the ultimate villain. But the shock that’s meant to cause is undermined by the predictability of the twist, which is compounded by a casting decision that puts an actor you just know is going to turn out to be a rotter at the center of it. (And the credibility of this final act is wrecked by casting as the American president an actor who looks very much like Howard Dean! Talk about implausibility.)

Still, you have to give “Salt” credit for trying to fashion a labyrinthine spy thriller, even if it winds up feeling terribly old-fashioned and passe. And you have to give credit to Jolie for all her exertions, though in the end the character of Salt winds up being little more than a series of transformations from one cardboard figure to another (including a kind of Natasha Fatale). And you have to credit Phillip Noyce for directing it efficiently, although there’s a certain grimness to that efficiency and the result is no improvement on his Tom Clancy adaptations of the nineties.

But unhappily to go along with the virtues are major flaws. Wimmer’s dialogue ranges from pedestrian to awful, with some downright howlers, and the illogic of much of the action is enormous. Some of the effects have a rather cheesy look. And apart from Jolie and Olbrychski, the cast is pretty much wasted in rote roles; even the usually reliable Ejiofor can do nothing with his.

At one point in “Salt,” somebody remarks that if the heroine can get away with something given all the precautions against her, it will be pretty amazing. Unfortunately, the movie isn’t. Its energy masks its vacuity for a while, but the brain-free emptiness ultimately wins out.