Who is Madame Nourisson from Cousin Bette: Part One of Poor Relations and what is their importance?

Madame de Saint-Estève, who is also known as Madame Nourrisson, is a lower-class woman of dubious integrity. She is a shadowy figure, whose specialty is planning murder for an enormous fee. Nourisson and her associates are particularly talented in the art of arranging "accidents." Victorin Hulot makes contact with Nourisson through the Paris Police.