In the early morning, while the city of Lourdes is still sleeping, the body of Doctor Delubac is discovered in one of the basins of the cave of the apparitions, where pilgrims come to immerse themselves. Fiona Langlois, police commander and child of the country, supported by Maxime Gardette, newcomer to the police station, will investigate the death of this man who was part of the CMIL - International Medical Committee of Lourdes. This committee, which studies and validates so-called "miraculous" cures, was to meet the next day to rule on the files of former patients. Did Delubac's research threaten powerful interests? Fiona and Maxime go through the patient files.