During the July 13, 1917 apparition, Our Lady gave the three children a three-part secret. The first two parts were revealed in Sister Lucia’s letter to her Bishop on August 31, 1941.
The First Part of the Secret: The Vision of Hell
You have seen hell where the souls of poor sinners go. To save them, God wishes to establish in the world devotion to my Immaculate Heart. If what I say to you is done, many souls will be saved and there will be peace. The war is going to end; but if people do not cease offending God, a worse one will break out during the pontificate of Pius XI. When you see a night illumined by an unknown light, know that this is the great sign given you by God that He is about to punish the world for its crimes by means of war, famine, and persecutions of the Church and of the Holy Father.
The Second Part of the Secret: Devotion to the Immaculate Heart of Mary
The Third Part of the Secret
The third part of the secret was requested of Sister Lucia by the Bishop of Leira when she fell seriously ill in mid-1943.
At the left of Our Lady and a little above, we saw an Angel with a flaming sword in his left hand; flashing, it gave out flames that looked as though they would set the world on fire, but they died out in contact with the splendor that Our Lady radiated toward him from her right hand. Pointing to the earth with his right hand, the Angel cried out in a loud voice: ‘Penance, Penance, Penance!’ We saw an immense light that is God, something similar to how people appear in a mirror when they pass in front of it, a bishop dressed in white (we had the impression it was the Holy Father), and other bishops, priests and men and women religious going up a steep mountain, at the top of which there was a big cross of rough-hewn trunks as of a cork tree with the bark. Before reaching there, the Holy Father passed through a big city half in ruins, and have trembling with a halting step, afflicted with pain and sorrow, he prayed for the souls of the corpses he met along his way. Having reached the top of the mountain, on his knees at the foot of the big cross he was killed by a group of soldiers who fired bullets and arrows at him, and in the same way there died one after another the other bishops, priests, men and women religious, and various lay people of different ranks and positions. Beneath the two arms of the cross there were two Angels each with a crystal aspersorium in their hand, in which they gathered up the blood of the martyrs and with it sprinkled the souls that were making their way to God.
The third part of the secret was published by the Vatican on June 26, 2000.
Read the Theological Commentary and Vatican statements about the Message of Fatima.
The above is taken with permission from the World Apostolate of Fatima website.