The basic plot concerns a successful lawyer (Melvyn Douglas) in 19th century Louisiana, who chooses to marry Frou Frou, the spirited and lively sister of more wholesome, reasonable Louise. Although Louise is in love with Douglas, she advises her sister to marry him. Their marriage starts off well, but soon Douglas resents his wife for not being an adequate homemaker, as Louise would have been (Frou Frou is 'too nice, and not strict enough with the slaves'). He soon has Louise coming to live with them and taking over the normal duties of his wife.
Frou Frou gradually realizes her place in the home is nothing more than as a 'Toy Wife,' someone for her husband to make love to while Louise takes her place in the home as mother. This causes her to look for true love elsewhere, and finding it in another suitor (Robert Young). This has disastrous repercussions for everyone involved.
It would be unfair to label Frou Frou a femme fatale. She is too kind, too loving, and much too wise. The true villain of the piece is Melvyn Douglas, who wants it both ways. He wants a reasonable, hardworking woman like Louise to take care of the house and Frou Frou to take care of the sex. At one point in the film, Louise confronts him and says so, and thus he is finally able to question the kind of husband he has been.
The acting in the film is variable. Douglas is good as the fickle husband, who only finds error in his wife instead of looking within himself. Rainer has moments of brilliance but her acting style is difficult to get used to, and is glaringly different from the more restrained performances from the other actors.
The production, however, is a first class star vehicle for Rainer, who was usually not given the attention two Oscars warranted. Overall, an interesting and, at times, moving melodrama with a central character who was basically good and should not be dismissed as a femme fatale.