In post-World War I Europe, two inseparable friends, Jules, a shy German, and Jim, a charming Frenchman, both adore the arts and literature. Their friendship is robust and unwavering until they encounter the free-spirited Catherine, who captivates both men with her vibrant personality and unconventional charm. Jules quickly falls in love with her and eventually marries her, hoping to preserve their unique bond and maintain harmony within their trio.

As the years pass, shifting dynamics and personal desires create tensions within their relationship. Catherine's restless nature and yearning for freedom begin to strain her marriage with Jules and complicate her bond with Jim. The friends' attempts to maintain their deep connection are continually challenged by Catherine's unpredictable actions and emotions. This complex interplay of love, loyalty, and personal growth among the trio forms the heart of the tale, exploring the intricate balance between friendship and romance in a changing world.