Sylvie, a young woman who believes to be cursed, lives in the town of Carcassonne with her guardian, Mr. Toulzac. He is a retired teacher who wishes to discover the secret of the Cathars, a Christian sect of the Middle Ages that glorified death over life. Sylvie meets Roland, a composer who instills new hope into her troubled mind. Mr. Toulzac then asks her then to renounce the world and go down a secret tomb he has just found.

In 1914, in the first months of World War I, Louise Jarraud loses her husband, killed on the front. Shortly after, she gives birth to a baby, who soon dies. Devastated by this double misfortune, Louise decides to dedicate her life to caring for the children of others. She becomes a nurse with several employers, giving her affection to little boys or girls. A widower and another man propose to her but she refuses twice determined as she is to live only for the children in her charge.

Maigret is called to the high-class Hotel Majestic to investigate a body. The wife of a wealthy American has been killed - but to Maigret's surprise she has a gun in her purse. He begins to follow up the handful of clues that could explain her secret life and her demise.