They are young, they are beautiful, they love each other, life belongs to them. Until tragedy. One morning, Alex's body is found at the bottom of a cliff. The inquest concludes a suicide. Sarah's life is falling apart. Back in Lyon, Sarah, steeped in grief, still does not understand what pushed her husband to commit the irreparable. Until she receives a letter from Ardèche. A passionate love letter from a stranger, Inès, addressed to her husband. Sarah then makes a decision: she must find this woman. This may be his only chance to get the answers to the questions that obsess him.