Brilliantly portrayed in adulthood by Déborah François, Hélène Jegado (1803-1852) was an adorable child who grew into what appeared to be a charming young woman. Born dirt-poor on a farm in uneducated and ultra-superstitious Brittany in the early 19th century, she was isolated and unloved, her head filled with morbid thoughts that led her to be tormented and vengeful despite her outwardly calm demeanour. She became the worst serial killer in history, using first the wild blueberry-like Belladonna and later arsenic to poison people at random during her employment as a cook and housekeeper.
 
Director Stéphanie Pillonca-Kervern adapts Jean Teulé’s recent biography of Hélène Jegado and re-creates the era with incredible authenticity.