What a bummer, man, to end up battered, bloodied, handcuffed, and shackled to a stainless-steel table in a room deep in the bowels of some government facility. "How did all this happen?" an interrogator asks the hapless Mike Howell (Jesse Eisenberg), which triggers a flashback montage full of stroboscopic spoilers: fireworks, a frying pan, drawings of a monkey, an exploding car, a cup of instant noodles spattered with strawberry-red blood. It's been one hell of a night for this mild-mannered stoner, and over the next 95 minutes, Mike's going to spill the bong water about what went down. The stoner-comedy formula has remained mostly unchanged since it solidified in Cheech and Chong's Up in Smoke (1978): harmless high jinks, cartoonish authority figures, trippy improbabilities, and above all, a bud-fueled devotion to a male best bud. The first clue that American Ultra seeks to break the subgenre's rules is that Mike's closest relationship is with his sleepy-eyed, tangle-haired girlfriend Phoebe (Kristen Stewart). The two live in stoner domestic bliss in a shabby trailer in a backwoods Virginia town, sleepwalking through marginal employment (him: a convenience store; her: the night shift for a bail bondsman), smoking up, snuggling, and sporting matching tattoos. It's something close to heaven, until a precisely groomed woman from nearby Langley walks into Mike's store and utters a string of code words that awaken his dormant programming as a super-soldier killing machine. This violent fantasy of slacker wish fulfillment would suffer greatly without the considerable charms of its two stars. Jesse Eisenberg is surprisingly believable as an action hero, sacrificing none of his adorkable appeal while going bloody mano a mano with his foes. Meanwhile, his chemistry with Kristen Stewart is believable and heartfelt, and she finds just the right grace notes to portray a woman whose sincere devotion to her boyfriend is constantly warring with her frustrations over his limitations. The smaller roles also contain a number of good performances, including Topher Grace's usual excellent work as a smarmy jerk in a suit, Arrested Development veteran Tony Hale as a dainty bureaucrat, and Walton Goggins as the kind of cackling creep who used to be played by Flea in Penelope Spheeris' movies. But be warned: Though the studio is selling this as a stoner comedy, it's really not. It's the heretofore-unseen strange beast of a stoner action flick, owing more to Repo Man and Natural Born Killers than Dude, Where's My Car?, and it is not a mellow buzz. There's a ton of splattering brutality, including meat cleavers to the skull and executions in the mud, along with a healthy dollop of '90s-style nihilism, cynicism, and suspicion (all that's missing is a mention of Area 51). Is it fun? Well, cult-film fanatics will certainly like it, if only for the fact that it has the courage to be the movie that the execrable and confused Wanted tried to be. (NORML activists will also appreciate its depiction of habitual marijuana smokers not as Jeff Spicoli-esque buffoons, but as bright, thoughtful, creative, and capable people who would rather have a buzz than a panic attack.) American Ultra might not be your (dime) bag, but in a summer full of remakes and superheroes, at least it's got the chutzpah to attempt something new.