At a gas station one night, Pierre (Pinon), the slaving ghost writer to a famous trash novelist, watches Huguette (Dana) get stranded after her fiancé dumps her and drives off. Pierre offers to give her a lift, and before long Huguette pleads with the man to impersonate her fiancé as she takes him to meet the parents. Oh, did I mention that a serial killer’s on the loose—who may be the man who’s just picked her up?

Roman de Gare, whose title translates roughly to the kind of book you take to the beach or read on an airplane, wears many hats: serial-killer thriller, whodunit, comedy, love story and—that old reliable—a mild satire of celebrity, Famous Writer Division. Each on its own has moments of diversion, but because all must jostle for screen time, the movie fails to fully tap any of them. And the tone shifts unsatisfyingly between something approaching menace and the calmer waters of romantic comedy.

Still, the love story is unexpectedly sweet. Dana’s amazing face is both young and world-wisened; she is captivating as a hairdresser who’s screwed up her life but knows she deserves better. And Pinon, whom American audiences may recognize from his turns in Amélie or Alien: Resurrection, proves a charming leading man: With his face like a pug dog’s, he conveys both sympathy and mystery. Their relationship is as improbable as it is satisfying.