Following the premiere of her latest picture Viviane finds herself with a dead man in her apartment. Frédéric is a writer who's been falsely accused of murder, thanks to Viviane. Viviane has fled Paris for Bordeaux with a cabinet minister, and once Frédéric escapes from prison, he is not far behind. Once they reach the city, which is in chaos, they become entangled in a plot involving a rickety physicist, his endlessly resourceful assistant, an amiable ex-con, a shady reporter and several bottles of heavy water that absolutely, positively must not fall into the hands of the Germans.