Be­hind the Vat­i­can’s me­dieval walls, 133 car­di­nals gath­ered for Mass on Wednes­day morn­ing in prepa­ra­tion for the start of a con­clave to elect a suc­ces­sor to Pope Fran­cis.

At 4:30 p.m. (1430 GMT; 10:30 a.m. EDT), the car­di­nals will walk in­to the Sis­tine Chapel, chant­i­ng the med­i­ta­tive “Litany of the Saints” and the Latin hymn “Veni Cre­ator,” im­plor­ing the saints and the Holy Spir­it to help them pick a pope.

Once there, they pledge to main­tain se­cre­cy about what’s about to tran­spire and to not al­low any in­ter­fer­ence from out­siders to in­flu­ence their vot­ing.