One opening night at the Opéra Garnier, Louis Craon, an internationally renowned conductor, gives the Nazi salute. The shock is so great that no one in the pit or the hall dares move, no one except a violist, Sébastien Armant, who rises and turns his back on the conductor. Relayed instantly by the media, this almost involuntary gesture turns Armant into a hero, “the man who said no,” until a shadowy extremist group claiming Craon’s gesture makes him its target. A gripping day-by-day account of a life turned upside down, and an original meditation on ordinary obedience and heroism.