In this image released by Lionsgate, John Leguizamo, left, and Jesse Eisenberg appear in a scene from "American Ultra." (Alan Markfield/Lionsgate via AP)

Late August is often a dumping-ground for movies. Failed blockbusters, genre misfires, flat comedies, and third tier action films.

But every so often a good flick slips in during these dog days of summer and we have one such film.

“American Ultra” is a smart mashup of a lot of typical summer fare: a little bit love story; a lot more stoner comedy; and most of all, a sort of sci-fi spy thriller with plenty of violence and massive explosions thrown in for good measure.

Jesse Eisenberg stars as a slacker convenience store clerk Mike Howell, who loves his girlfriend almost as much as he does his weed. Howell is a stoner through and through and considers himself something of a loser since he can’t ever seem to get his life together. He smokes to allay his many anxieties, which often manifest themselves as panic attacks whenever he tries to leave town.

His slacker life starts to change when a mysterious woman, played by Connie Britton, approaches the store counter and says: “Cherry progressive, listen. Man of red is set in motion. Echo choir has been breached.”

But Eisenberg’s character doesn’t have a clue as to what she’s saying and the woman leaves in frustration. Not long after, however, he confronts two bad guys who’re messing with his car in the parking lot. When the two armed men attack him, he suddenly turns into a top-notch assassin. Armed only with a spoon, he expertly disarms and kills both men. He’s high, of course, and now even more paranoid than usual. He can’t quite believe what just happened, anymore than his girlfriend who rushes to his side.

“I shot those guys in the head, and that guy, I like, spooned him in the neck and it just like ended. They were trying to, like, stab me Pheobe,” Howell says to his girlfriend played by Kristen Stewart.

“I am like freaking out all over the place, babe, I have a lot of anxiety about this,” he says.

Thus begins the gradual unraveling of an elaborate undercover CIA plot that Eisenberg’s character is unknowingly in the middle of.

Take away our hero’s drug use and this could easily be the plot line for a new Mission Impossible, Jason Bourne, or even Bladerunner movie. And the movie takes its action sequences quite seriously and doesn’t flinch on the violence quotient either.

Howell may be a slacker, but for some reason unknown to himself, he’s a trained killer. As the trailer proclaims, he’s a “stoned” cold killer. Imagine Matt Damon’s Jason Bourne as a stoner and you’ll have a good idea of how this movie works.

And for the most part, “American Ultra” does work. It’s fun to watch Eisenberg gradually become more and more aware of his long-suppressed mental and physical prowess. After stumbling through most of his life, he finds himself suddenly feeling “amazing,” even though he’s now fighting for his life at every juncture.

The movie’s energy sags somewhat in the middle but it closes strong. All is eventually revealed; who he is and why he is that way.

And throughout, the film manages to stay true to its stoner roots while satisfying the genre demands of the action picture. The key is its comic tone. As violent as the movie gets &#8212 and it gets very violent &#8212 there is always an underlying sense of humor about the proceedings. It’s as if the movie is both reveling in and mocking the very attributes of the blockbusters it’s now displacing at summer’s end.

That’s stone cold funny. Or stoned-cold, if you prefer.