Nima Nourizadeh’s American Ultra is a bloody valentine attached to a bomb. It’s violent, brash, inventive and horrific, and perhaps the most romantic film of the year. Jesse Eisenberg and Kristen Stewart star as Mike and Phoebe, two West Virginia stoners blissed out on weed and each other. “We’re the perfect fucked-up couple,” Mike beams before admitting that she’s perfect and he’s the fuckup. And as the movie starts, Mike has scraped up the cash for a chintzy engagement ring so he can spend the rest of his life kinda ruining hers: having panic attacks that prevent them from traveling, forcing her to cook lest he burn down the house, and supporting them on his meager paycheck from the mini-mart.

With other actors, this could play like slapstick. But Eisenberg mines Mike for pathos: He’s not a punchline; he’s a flake who knows he’s his own worst enemy. There’s a Mike in every town, a smart guy who can’t stop screwing up.

Yet it’s Stewart who makes this loony love story work. She takes what could easily be a simple supportive-girlfriend role and fills Phoebe with a rainbow of emotions. Phoebe looks at Mike like she sees exactly who he is and picks him anyway. She knows how much of their future is on her shoulders. As the hostile local sheriff chides, “You’re his girlfriend, you’re his mom, you’re his maid, you’re his landlady.” True, but she’s still no pushover.

The big twist is that none of us know exactly who Mike is — not even Mike. One night outside the Cash & Carry, Mike looks up at the stars, and this disheveled domestic drama turns into a thriller. The camera zooms up to a satellite and then beams to CIA headquarters, where a garbled caller informs Agent Lasseter (Connie Britton) that Mike will be murdered within 24 hours. Agent Yates (Topher Grace), a vile twerp, commanded the execution and shipped twenty killers to West Virginia, including a repellent hick named Laugher (Walton Goggins) whose exhalations through his missing teeth sound like a ghost whistling across a grave.

It’s no shock to movie-goers that Mike has been programmed with surprise skills, though it is to him. “I could list, like, fifty types of tanks right now,” he exclaims after Lasseter activates him so he can try to stay alive. We’ve seen that plot point in a dozen dumb movies. What is shocking is how smart American Ultra is at being dumb: Its emotional intelligence is off the charts. Max Landis’s script isn’t the usual whiz-bang wish fulfillment that assures us that even losers can be special. It’s a real romance about two people trying to survive, and Eisenberg captures the horror of suddenly realizing your life has been a lie. “What if I’m a robot?” he bleats. Once again, it’s up to Phoebe to steady her fragile man — and the movie around him. “You’re not a robot,” she insists. Would a robot wail after stabbing a man with a spoon? Would it decide it would rather stop fighting, crawl into bed with a bong and die smiling?

What happens to Mike and Phoebe is hard to watch. Nourizadeh keeps the effects of violence painfully real: As the blood, bruises and busted lips rack up, we look at the lovebirds and wince. But the filmmaker is a sadist with a sense of humor. His fatal weapons include dustpans, skillets, frozen hamburgers and cans of tomatoes. He’s an ingenious director of action. No matter how crazy the brawl, we know the geometry of the scene, and we can follow Mike’s intentions with an eye-flick.

Better still, Nourizadeh is ruthless with the audience’s empathy. Villains have moments of heart; good people wind up on the wrong end of a gun. And he’s got the control to both hold a camera still when fists are flying and whip us into frenzies with a wild montage, ripping through Mike and Phoebe’s relationship at light speed without skimming past its soul.

American Ultra is astonishingly alive. It feels at once young and angry, unhinged and sincere, like a teenager scribbling “Screw you” to everyone but his first crush. It’s laced with jokes but aimed deeper into our guts. Any movie could shoot a scene of Jesse Eisenberg emerging from a cloud of smoke in a bloody Hawaiian shirt for laughs. Only this movie could do it to make you cry.