Diane de Poitiers (Lana Turner) becomes the mistress of Prince Henri (Roger Moore), second in line to the throne.

Catherine, now ruling as regent for her three young sons, banishes Diane but spares her rival's life in a gesture of mutual respect.

The film was based on a fifty-page unpublished manuscript called "Diane de Poitiers" by John Erskine, who died in 1951.

Knopf re-secured the film rights from Erskine's estate and took the project to Dore Schary, head of production at MGM, where Knopft had a deal.

Actually she was a forerunner of today's modern woman; she was Europe's first outdoor girl, a health fan and an advocate of the cold bath.