On November 30, 1433, the Sorgue and the Rhône together flooded the lower streets of Avignon. In the small Chapel of the Holy Cross, where the Brotherhood of the Grey Penitents had begun a Forty Hours' Devotion the previous day with the Blessed Sacrament exposed, the floodwaters rose rapidly. The brothers ran with boats to rescue the Eucharist.
Reaching the locked door of the chapel and pushing it open, they expected to find the chapel knee-deep in water and the monstrance floating or sunk. Instead they saw the chapel full of water on both sides — but a clear dry passage from the door to the high altar, with the monstrance untouched. They retrieved it with dry feet. Several witnesses to the event left sworn testimony.
The Avignon antipope of the time, Felix V (Amadeus of Savoy), and the legitimate pope after the schism's resolution, Eugene IV, both confirmed the public cult. The Chapelle des Pénitents Gris on the Rue des Teinturiers still preserves the original chapel and the records.