In 1891, Léonie Vernier is a young girl living in Paris until an invitation from her uncle's widow Isolde prompts a journey to the Carcassonne region with her brother, Anatole.

Unknown to Léonie, her brother had been having an affair with Isolde and is being pursued by her jealous former lover, Victor Constant.

In the present day, an American, Meredith Martin, is in France to research the life of Claude Debussy for a biography she is writing.

During the visit, she uncovers information that links her lineage to that of Léonie Vernier and discovers the truth about the events in Carcassonne during that period in history.

Most of the action takes place in the Domaine de la Cade, a stately home in Rennes-les-Bains, which in 1891 is owned by Léonie's deceased uncle Jules and his wife Isolde, whom Anatole later marries.