Set in pre-WWI Vienna, Mascarade concerns a near-tragic misunderstanding over a nude painting. It is incorrectly assumed that heroine Leopoldine (Paula Wesseley) posed for the painting, when in fact the model was Gerda (Hilde von Stolz), the wife of stuffy Dr. Harrandt (Peter Peterson). The romance between Leopoldine and artist Heidendeck (Adolf Wohlbruck) is threatened when his cast-off mistress shoots him. Dr. Harrandt is summoned to perform an emergency operation on Heidenbeck, but upon discovering that the artist had painted his wife Gerda in the nude, the "good" doctor refuses to minister to Heidenbeck's wound. It is Leopoldine who appeals to the doctor's essential humanity and finally sets things right.