Born in 1247 to a farming family in a small village outside Perugia, Margaret of Cortona was willful and reckless in her youth. At age seventeen, she became a wealthy man’s mistress—even bearing his son out of wedlock. But her life of sin ended when she found her lover murdered. Devoting herself to prayer and penance, Margaret eventually joined the Third Order of St. Francis and took a vow of poverty. She established a hospital for the poor and homeless at Cortona. On divine command, she challenged her own bishop for his lavish and warlike lifestyle. Canonized by Pope Benedict XIII in 1728, she became a patron saint of the downtrodden, including the falsely accused, homeless, orphaned, and mentally ill, as well as midwives, penitents, single mothers, reformed prostitutes, and third children. For François Mauriac, Saint Margaret of Cortona became a source of fascination and solace during the Nazi occupation of France. During that time, feeling himself and all his countrymen to be among the downtrodden, he wrote this biography.