Declaration of War is the hippest kid-with-cancer movie you’ll ever see. Adam’s parents go to clubs and parties. They dance. They ride a motorcycle. They smoke. They embraced this lifestyle before their son was born, but throughout the film they don’t quit it. Having a 2-year-old with a brain tumor is stressful, it turns out.

Directed and co-written by star Valérie Donzelli, the film’s a weepie, but it also isn’t. It’s devastating to watch a tiny toddler being wheeled off to surgery, confused by the strangers and the bright white around him. And Romeo (co-scripter Jérémie Elkaïm) and Juliette (Donzelli)—yes, those are their names—receive as much bad news as good. But the tone of the film, aided greatly by an ever-present soundtrack spanning from classical to house, is relentlessly measured, verging perhaps a little too precariously on the upbeat. Declaration of War is more about survival than death—the survival of a handsome couple’s love-at-first-sight, their devotion to each other through sickness and health despite having never exchanged wedding vows.

What might be most remarkable about this eminently watchable film is its context: The stars are real-life romantic partners, and they had a seriously ill child themselves. So Declaration of War is essentially a roman à clef; it couldn’t have been easy to live through this ordeal twice. The film opens by nearly giving away the end, and then flashes back to the charged moment when Romeo and Juliette meet. They soon have Adam, but his constant crying, vomiting, and issues more serious still make them miserable—and then terrified—fast. “The kid is tyrannizing us,” Romeo barks, though eventually he’s the one who translates bad vibes into serious concern.

Declaration of War sometimes unfolds like a thriller, with early scenes intercut with shots of cells and a beating heart. At other times, it’s more like a terrible fairy tale, with anonymous others—not even characters in the movie—narrating the story. Whatever it’s doing, the film keeps your sensibility just slightly off-kilter, particularly when Romeo and Juliette, separated for a day but on their way to reuniting, break out into song. (Forgive them that. It doesn’t happen again.) In addition to the music and the couple’s partying, there’s lots of movement here: Juliette runs through hospital hallways after she hears Adam’s diagnosis, the couple run and play for sport, the family runs on the beach. Taken overall, the effect is an enthralling life-goes-on message. And life, ironically, is one thing this film’s full of.