In the novel Death in the Clouds, Maître Alexandre Thibault is the lawyer of Madame Giselle. He is described as a "tall elderly Frenchman with a grey beard". He speaks English slowly and and precisely, with a slight accent.
At the inquest, he testifies that the deceased is his client, Marie Angélique Morisot, who was known professionally as Madame Giselle. He says that she was one of the best-known moneylenders in Paris, and that many of her clients were English, and were people from the upper and professional classes.
Maître Thibault handled Madame Giselle's legal business, but she kept the control of her business in her own hands.
After the inquest, Maître Thibault tells Poirot, Chief Inspector Japp and M. Fournier that Madame Giselle had made a will many years before, leaving a small legacy to her maid, and the rest of her fortune to her daughter, Anne Morisot. He estimated the size of Madame Giselle's fortune to be eight or nine million francs.