A million worshipers streamed toward the shrine of Our Lady of Fatima in the Portuguese village 70 miles north of Lisbon. Many were swarthy peasants in thick shawls and rough clothing and had been traveling on foot for days. In family groups under shade trees or in makeshift tents, some ate fare brought from home—cheese, bread, olives, wine—and waited for another, more exalted pilgrim, Pope John Paul II. On May 13, 1981 he had been shot by a Turkish gunman in St. Peter's Square. Shortly thereafter the Pope had noted "a mysterious coincidence"—the attack came on the 64th anniversary of the first vision of the Virgin Mary at Fátima. And so he planned this journey of public thanksgiving.

Then, incredibly, it happened again—a second assassination attempt on the Pontiff exactly a year after the first. Out of the throng at Fatima, a renegade Spanish priest, Juan Fernández y Krohn, 32, lunged at John Paul with a 14-inch bayonet. Alert guards grabbed the assailant, preventing a catastrophe.

Undeterred, the Pope continued his homage at the shrine. Before the attack he had announced to a throng of 300,000, "I have come to thank Divine Providence in this place, which the Mother of God seems to have chosen in a particular way."

The papal presence at such a holy place focused attention once more on the question of miraculous apparitions. Since 1830 the Roman Catholic hierarchies have conducted local inquiries into at least 186 purported visions of the Virgin, of which only 10 have been deemed "authenticated." At Fátima, the Pope greeted the Carmelite nun Sister Lucia dos Santos, who is the lone survivor of the three shepherd children who claimed to have seen the visions there in 1917. As they later retold their experience, Lucia, with her cousins Francisco and Jacinta, saw a lightning bolt that May day, although the sky was clear. When they sought shelter under an oak, there was a second flash and a vision above the tree of, in Lucia's words, "a young lady, surrounded by light. The lady said, 'Don't be afraid.' "

At the Virgin's instruction, the children said, they returned to the site at the same hour on the 13th of each month. On the sixth month an estimated 60,000 people assembled in a driving rain to witness the apparition. The children claimed to have seen not only the Virgin but Joseph and the Holy Child as well. No one else did, although many saw through a break in the clouds an emerging sun "dancing" or "rotating," a sight that first brought panic, then "tumultuous" devotion.

Most intriguing were three secrets reputedly entrusted by the vision to the children. First, the existence of hell was confirmed by a brief glimpse of "a vast sea of fire." The second was surprisingly political: that Russia would wreak mischief on the world unless it is returned to the Christian fold. The third secret, reportedly written down by Sister Lucia and later sealed in the papal safe, has never been revealed. There was even speculation that John Paul would announce the final secret, if one exists, during his Fátima pilgrimage. He did not.

Today, along with Lourdes in France and Knock in Ireland, Fátima ranks among the major sites for worship of the Virgin, attracting three million annually. But it was not until 1930, 13 years after the visions, that the church declared Fátima "worthy of belief."

If anything, the church now moves even more cautiously toward authentication. "In fact," notes one Roman authority, "the faithful themselves prove to be the best judges." Only when they tend to return in ever greater numbers does the local bishop appoint an investigative committee to weed out clear cases of hallucination or blatant political or commercial motives. The Vatican does not officially recognize any site or apparition, though individual Popes may, as Pius XII, Paul VI and now John Paul II have at Fatima.

Despite the formidable obstacles to recognition, there has been no shortage of new claimants. Among them:

•In the Portuguese village of Tropeço pilgrims visit the farmhouse of Maria Rosalina Vieira, 18, who claims to have been visited by the Virgin six years ago. Two years after that, say devotees, she stopped eating and drinking altogether. Less charitable reporters have termed Rosalina the richest woman in Portugal. "I have two bank accounts," she once admitted. "After my death, which I feel is imminent, I will give them for good works."

•In the grimy coal-mining town of La Talaudière, France, a 14-year-old schoolgirl named Blandine Piegay says she has seen the Virgin Mary 31 times. This spring, according to Blandine, the Virgin asked her to convene an assembly in the backyard of her small home on Easter Sunday. "At 2:25 p.m. I saw her," Blandine recalls excitedly. "She was all in white with a blue veil, a gold cross and the face of a young girl." No one else saw the vision.

•In the mountain village of Medjugorje in the Yugoslav Republic of Bosnia-Herzegovina, four teenage girls tending sheep last June said they saw a vision bathed in light. One girl fell to her knees exclaiming, "The Madonna!" but the others fled. The next night, joined by two boys, all six saw the apparition, who advised them, "You must remain firm in the faith." As the "new Fátima" drew tens of thousands of pilgrims, Yugoslavia's Communist regime, always suspicious of large assemblies, cracked down.

If all this ferment disturbs Pope John Paul, he gives no indication. If anything, his reverence for the Virgin is ever more fervent. Recalling the earlier assassination attempt, he has told throngs in St. Peter's: "For everything that happened to me on that day, I felt that extraordinary motherly protection and care, which turned out to be stronger than that deadly bullet." As for the latest would-be assassin in Fatima, John Paul merely makes a disparaging gesture, followed by the sign of the cross—in forgiveness.