The differences in legalities and cultural mores of French and Americans regarding sex, love, marriage, religion, and family bonds are presented through the interactions of two families related by marriage. American Isabel Walker (Kate Hudson) heads to Paris to visit her half-sister, poet Roxeanne de Persand (Naomi Watts), who is pregnant with her second child. Isabel arrives to find that Roxy's French husband, Charles-Henri de Persand (Melvil Poupaud), has just left her, and the sisters later learn that he has fallen in love with another woman, who is married. Roxy and Charles-Henri deal with their break-up; Roxy doesn't want it but must face its legal consequences, including determining the ownership of a possibly-valuable French painting that has been casually in the Walker family for years, but which Roxy has had in her possession since she got married. Meanwhile, Isabel begins to explore all that France offers, including embarking on sexual relationships with two men. One is Charles-Henri's older maternal uncle, the wealthy and well-appointed Edgar Cosset (Thierry Lhermitte), who is already married and who is using the same playbook on her that he has on countless women before her. As groups and individuals within the two families disagree and argue about certain issues they are facing, it does not necessarily affect other issues and relationships between the two families based on their priorities and those cultural and legal standards.