Every evening at nightfall, Marius –in his 30s and mute-- comes to see his mother before she goes on stage at the cabaret where they live and work. Despite being in her sixties, Simone remains the diva of the Crazy Heart, the cabaret of this small port town. She performs as a seductive siren for passing sailors.
But the arrival of Josephine, a mysterious young woman who has come to replace the barmaid, soon turns this little world upside down: Josephine secretly dreams of singing, and Marius, for his part, seems to be rather charmed by her…