After a masked carnival ball, Gerda Harrandt, wife of the surgeon Carl Ludwig Harrandt, allows the fashionable artist Ferdinand von Heidenick to paint a portrait of her wearing only a mask and a muff. This muff however belongs to Anita Keller, in secret the painter's lover but also the fiancée of the court orchestra director Paul Harrandt. The picture is then published in the newspaper. When Paul sees it and asks von Heidenick some questions about the identity of the model, the artist is forced...