Murder of Laetitia Toureaux
Lætitia-Marie-Joséphine Toureaux (née Nourrissat; 11 September 1907 – 16 May 1937) was a murder victim who was found stabbed to death inside an empty Paris Métro carriage. Further investigations into her death later revealed that other than working as a factory worker in the day, she worked as a spy to infiltrate the La Cagoule, a far-right terrorist group, who may have been behind her death.
Source: Wikipedia — Murder of Laetitia Toureaux (CC BY-SA 4.0)