As a young woman, Eugénie (Lou de Laâge) discovers that she has the special power to hear the dead, but when her family discovers her secret, she is taken to La Pitié Salpétrière Hospital.
The hospital is a neurology clinic in Paris run by Dr. Charcot (Grégoire Bonnet), a famous professor and pioneer of neurology, where women diagnosed with hysteria, "craziness," egomania, epilepsy and other types of mental or physical diseases are committed. Eugénie's destiny becomes entwined with that of Geneviève (Mélanie Laurent), a nurse at the hospital, whose life is passing her by. Their encounter will change both their futures as they will prepare for the annual "Bal des folles" organized by Dr. Charcot at the hospital.
Based on the novel Le bal des folles by Victoria Mas.