Once upon a May 13, 1917 three children – Lúcia, Francisco, and Jacinta – were tending to a flock of sheep in a grotto outside of Fátima, Portugal, when a bolt of lightening struck the earth. A woman surrounded by a light ‘brighter than the sun’ appeared before them. She told the children they needed to pray the rosary everyday to help bring peace to the world, and then exhorted them to return to the same place at the same time on the 13th of every month for further instructions.

The children obeyed, and the woman appeared to them another five times. Word of the apparitions spread throughout the land, and every month more and more people showed up at the grotto to see for themselves what the children had claimed.
It was on the occasion of the third appearance – July 13, 1917 – that the woman in light imparted upon the children three secrets.
Now, everybody loves a good secret. Unless, of course, you’re the government of Portugal and you’re deeply involved in World War I. The appearance of probably-the-Virgin-Mary professing a path to peace was certainly a welcome sign to the people, but to the government it meant trouble. It’s harder to win a war when your people aren’t enthusiastic about it. The church was accused of making up the story in order to get more people to mass on Sundays, and the children were even arrested and interrogated. To their credit, the kids stuck to their story.
On the occasion of the final appearance of “Our Lady of Fátima” in October 1917, thousands of people showed up to the grotto. Some claimed they saw the sun dancing in the sky. Others saw Mary, Jesus, and Joseph in the sun. Still others saw the sun as a whirling disc of fire (which is, in fairness, hard to refute). Some saw nothing at all. Newspapers across the country covered the event and soon there was mass hysteria about the secrets. What could they be?

The world wouldn’t find out what the secrets were for another twenty-four years, and then only from Lúcia, who had by that time had become a Carmelite nun.
The other two children died tragically in the 1918 influenza epidemic, which would claim more than 20 million lives throughout Europe. So the only other witnesses to a series of apocalyptic visions died in an actual apocalypse. Gah.

So, ok, the secrets.
In brief:
- Hell is real
- Russia needs to convert to Catholicism
- Someone is going to try to kill the pope
In not so brief:
Secret number one was a vision of demons and human souls suffering in Hell:
“Our Lady showed us a great sea of fire which seemed to be under the earth. Plunged in this fire were demons and souls in human form, like transparent burning embers, all blackened or burnished bronze, floating about in the conflagration, now raised into the air by the flames that issued from within themselves together with great clouds of smoke, now falling back on every side like sparks in a huge fire, without weight or equilibrium, and amid shrieks and groans of pain and despair, which horrified us and made us tremble with fear. The demons could be distinguished by their terrifying and repulsive likeness to frightful and unknown animals, all black and transparent. This vision lasted but an instant. How can we ever be grateful enough to our kind heavenly Mother, who had already prepared us by promising, in the first Apparition, to take us to heaven. Otherwise, I think we would have died of fear and terror.” – Sr. Lucia, in her 1941 memoir.

Secret number two was about converting Russia to Catholicism in order to stave off World War II. (I checked, the Portuguese pronunciation of Russia sounds nothing like Germany or Nazis; they couldn’t have heard it wrong):
“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 Pope 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. To prevent this, I shall come to ask for the Consecration of Russia to my Immaculate Heart, and the Communion of reparation on the First Saturdays. If my requests are heeded, Russia will be converted, and there will be peace; if not, she will spread her errors throughout the world, causing wars and persecutions of the Church. The good will be martyred; the Holy Father will have much to suffer; various nations will be annihilated. In the end, my Immaculate Heart will triumph. The Holy Father will consecrate Russia to me, and she shall be converted, and a period of peace will be granted to the world.” – Sr. Lucia, in her 1941 memoir

Secret number three was maybe, kind of about the assassination attempt of Pope John Paul II. There’s a lot of controversy about this last one. Lucia didn’t want to reveal it since the visage told her not to. But when she came down with a serious illness the bishop of Leiria demanded that she write the prophecy down. She did so, and sealed the envelope. It wasn’t to be opened until 1960.
“I write in obedience to you, my God, who command me to do so through his Excellency the Bishop of Leiria and through your Most Holy Mother and mine. After the two parts which I have already explained, 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 splendour that Our Lady radiated towards him from her right hand: pointing to the earth with his right hand, the Angel cried out in a loud voice: ‘Penance, Penance, Penance!’. And we saw in 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 that it was the Holy Father’. Other Bishops, Priests, 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 half trembling with halting step, afflicted with pain and sorrow, he prayed for the souls of the corpses he met on 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 his hand, in which they gathered up the blood of the Martyrs and with it sprinkled the souls that were making their way to God.” – Sr. Lucia, in her letter to the the bishop of Leiria.
My sources for this post were Wikipedia and my Lonely Planet guidebook.

Also at the main basilica are the graves of Lúcia, Francisco, and Jacinta. They honor the three shepherd children in a tasteful and sweet way.
Hundreds of thousands of people come here, especially on the 13th of May and October (the anniversary of the first and last visions) to pray and to seek guidance. Keep that timing in mind if you’re thinking of visiting around those months.
We recommend a visit here, though it won’t take even a half day to experience the place. We rented a car so that we could see a number of small sites like this one over the course of a few days and it made the various visits a lot more manageable.