In 1657, Cardinal Rospigliosi commissioned Nicolas Poussin to paint an ex-voto with the idea of paying homage to Saint Frances of Rome as the outbreak of plague was coming to an end. Who other than Poussin could have filled this strange scene with such dramatic tension, poetry and religious fervor? This exceptional painting, analyzed for the first time, was a novel subject matter for the artist, who signed his religious testament at over 60 years of age.