Helene Jegado was a 19th-century French domestic servant who used her role as a cook to poison the people around her with arsenic. Operating in rural Brittany during a time of limited medical knowledge, she was able to evade suspicion for years as victims died from mysterious illnesses. Eventually, patterns of death led to investigation, exhumation, and arrest. Convicted of multiple murders, she was executed in 1852. Her case remains one of the most disturbing examples of a serial poisoner operating within trusted domestic spaces.