Rendu was three years old when the Revolution broke out. Starting in 1790 it was compulsory for the clergy to take an oath of support for the Civil Constitution of the Clergy. Numerous priests, faithful to the Church, refused to take this oath. They were driven from their parishes, with some being put to death and others having to hide to escape their pursuers. The Rendu family home became a refuge for these priests, some fleeing to Switzerland. The Bishop of Annecy found asylum there under the assumed name of Pierre. Jeanne-Marie was fascinated by this hired hand who was treated better than the others. One night she discovered that he was celebrating a Mass.