When the young American Jesse accidentally meets the French girl Céline on a train from Budapest, he persuades her to get off the train in Vienna, where they roam the city for the night and experience an unforgettable journey.
Nine years after their romantic encounter in Vienna, Jesse meets Celine once again in Paris as he promotes his book, and they spend a day together catching up on their lives and their feelings for each other.
Almost twenty years after their first romantic encounter in Vienna, now the French-American married couple Jesse and Celine are spending a summer vacation in Greece, as they look back at their lives and question their past choices.