In “Salt,” Angelina Jolie plays an American double agent named Evelyn Salt trained as a Russian spy and inserted back into America as part of a plot to kill both the Russian and American presidents.

Or something like that. It’s all very confusing, really.

To save us from thinking too hard about the story line, Jolie puts herself through a series of stunts ranging from chilling to absolutely bloodcurdling with gusto.

When she’s not jumping from the roof of one speeding car to another, she’s escaping from a police cruiser by tasing the driver with his own gun — while handcuffed.

To actually attempt to describe the plot — Jolie plays a CIA agent accused by a Russian defector of involvement in a plot to kill the Russian president and begin a nuclear showdown resulting in the United States’ demise.

Thanks to brain scans and lie detectors they run on the defector while she’s in the holding cell, the CIA takes this threat seriously.

Soon Jolie is running from every cop in the country, and looking more and more guilty of being the Russian sleeper she was accused of being.

It’s impossible to say it’s not fun to watch. Like a James Bond movie, “Salt” is best if you forget the plot details that will ultimately go unexplained, and watch the spectacle as it unfolds.

Watching Jolie devise a rocket launcher from a fire extinguisher and some sort of handy chemical she happens across is marvelous. And if you’re male, so is the scene where she covers a security camera with her underwear.

Let’s see Bond pull out his undergarments from inside a tux.

But when the action lags, the movie is incredibly dull. In a Jason Bourne-like fashion, we slowly learn about Salt’s misunderstood past, dead family members and how she was brainwashed into becoming a killer.

You quickly realize, however, that it’s not going to make as much sense as the Bourne trilogy did, and instead forget about it.

Bourne enticed us because, even though he knew how to kill a man in five seconds, he didn’t know everything. There were other characters for him to, you know, talk to and learn from.

In contrast, Salt commits every action with unyielding certainty. There’s no trace of ambiguity in her mind. And her self-assuredness makes her boring.

Luckily, the movie doesn’t pause for build-up very often. When director Phillip Noyce does, it’s usually with a close-up of Jolie’s expressive face.

She’s a seasoned killer, yes, but when she’s staring painfully into the distance, you realize how this lifestyle is affecting her.

Then she crashes a police cruiser over the side of an overpass, and walks away unscathed, minidress-clad hips swinging, as you cheer her on to keep up the fight.

As the movie careens to an ending, the film’s booming soundtrack – an orchestral tour de force – seems unnecessary. Everyone in the audience has either already figured out who the bad guy really is (do you really think it’s going to be Jolie?) or didn’t care from the beginning.

“Who is Evelyn Salt?” That’s the question Noyce begs us to ask, but it never seems like we really need to know the answer.

It’s obvious from the minute her face appears on the screen that she’s Angelina Jolie, and she’s looking fabulous.

Grade: C