Before the second coming of Christ, Mormons believe that a secret gathering of all the great prophets from the past will take place in Adam-ondi-Ahman, Missouri.

“Until his grand council is held, Satan shall hold rule in the nations of the earth; but at that time thrones are to be cast down and man’s rule shall come to an end … Preparation for this work is now going on … This council in the valley of Adam-ondi-Ahman is to be of the greatest importance to this world. At that time there will be a transfer of authority from the usurper and impostor, Lucifer, to the rightful King, Jesus Christ … When this gathering is held, the world will not know of it; the members of the Church at large will not know of it, yet it shall be preparatory to the coming in the clouds of glory of our Savior Jesus Christ as the Prophet Joseph Smith has said. The world cannot know of it. The Saints cannot know of it – except those who officially shall be called into this council – for it shall precede the coming of Jesus Christ as a thief in the night, unbeknown to all the world.”

Joseph Fielding Smith, The Way to Perfection (Salt Lake City, UT: Deseret Book Company, 1984), 290-291.