Belle Johnson, a flirtatious widow in Paris for the carnival season, finds that the marriage of her sister Grace and Frank Morley is headed for trouble. Frank is very absorbed in his business, thus Grace has begun an affair with the handsome Sir Lionel Heathcote. Belle tries to save her sister from eloping with Heathcote by making him promise to drop the affair and return to England. Finding them going ahead with their plans, however, she steps in, at the risk of losing the respect of Jim Morley...