A couple lives in Paris with their daughter, who suffers from an incurable disease that forces her to live in an hermetic glass bubble. One day, a mysterious fog begins to spread in the Parisian streets, killing everyone who gets caught in it. The parents find shelter on the roof above the mist, but the daughter is still in her bubble in the now fog-filled flat. Her parents must now cope with the lack of food, power, and information, but also find a way to get her out, since the bubble won't hold forever.