The film tells the story of a young American woman Isabel Walker (Kate Hudson) who travels to Paris to visit her pregnant sister Roxy (Naomi Watts). Roxy's husband Charles-Henri left her for his lover Magda Tellman. Later on, Isabel secretly falls in love with her French uncle-in-law Edgar Cosset and becomes his mistress. Because of this, she becomes somewhat "popular" and because of being his mistress is showered with many gifts. Later, Roxy finds out that her husband has been murdered. The madness continues and it only goes downhill.