Baroness Irène de Rysbergue, neglected by her gloomy husband, is preparing for the ball. Admiring her feather-trimmed dress, her young son nicknames her "Maman Colibri". During the evening, she falls in love with Georges de Chambry, the officer friend of her oldest son. The adulterous couple is quickly exposed, and flee to Algeria where Georges is subject to military discipline. Maman Colibri meets the ravishing Miss Dickson, to whom her young lover is not impervious …