I’m in Medjugorje with a group of Americans, mostly hockey dads from the Boston area, plus two men and two women with stage 4 cancer. We’re led by 59-year-old Arthur Boyle, a father of 13, who first came here on Labor Day weekend in 2000, riddled with cancer and given months to live. He felt broken and dejected and wouldn’t have made the trip had not two friends forced him into it. But that first night, after he went to confession at St. James the Apostle church, psychological relief came rapidly.

“The anxiety and depression were gone,” he told me. “You know when you’re carrying someone on your shoulders in a swimming pool water fight—they come off, and you feel light and free? I was like, Wait a minute, what just happened to me? Why is that?”

The next morning, with his friends Rob and Kevin, he met another of the “visionaries,” Vicka Ivankovic-Mijatovic, in a jewelry shop and asked for her help. Gripping his head with one hand, she appealed to the Virgin Mary to ask God to cure him. Boyle said he experienced an unusual sensation right there in the store. “She starts to pray over me. Rob and Kevin put their hands on me, and the heat that went through my body from her praying was causing them to sweat.”

Back in Boston a week later, a CT scan at Massachusetts General Hospital revealed that his tumors had shrunk to almost nothing.

Since then, Boyle has been back to Medjugorje 13 times. “I’m a regular guy,” he said. “I like to play hockey and drink beer. I play golf.” But, he continued, “I had to change things in my life.” Today, Boyle said, he’s become “a sort of mouthpiece for Jesus Christ’s healing power and of course the Mother and the power of her intercession.”

Praying for the Virgin Mary’s intercession and being devoted to her are a global phenomenon. The notion of Mary as intercessor with Jesus begins with the miracle of the wine at the wedding at Cana, when, according to the Gospel of John, she tells him, “They have no wine,” thus prompting his first miracle. It was in A.D. 431, at the Third Ecumenical Council, in Ephesus, that she was officially named Theotokos, Bearer of God. Since then no other woman has been as exalted as Mary. As a universal symbol of maternal love, as well as of suffering and sacrifice, Mary is often the touchstone of our longing for meaning, a more accessible link to the supernatural than formal church teachings. Her mantle offers both security and protection. Pope Francis, when once asked what Mary meant to him, answered, “She is my mamá.”

Her reported appearances, visions experienced often by very poor children living in remote or conflict-wracked areas, have intensified her mystery and aura. And when the children can’t be shaken from their stories—especially if the accounts are accompanied by inexplicable “signs” such as spinning suns or gushing springs—her wonder grows.

Mary is everywhere: Marigolds are named for her. Hail Mary passes save football games. The image in Mexico of Our Lady of Guadalupe is one of the most reproduced female likenesses ever. Mary draws millions each year to shrines such as Fátima, in Portugal, and Knock, in Ireland, sustaining religious tourism estimated to be worth billions of dollars a year and providing thousands of jobs. She inspired the creation of many great works of art and architecture (Michelangelo’s “Pietà,” Notre Dame Cathedral), as well as poetry, liturgy, and music (Monteverdi’s Vespers for the Blessed Virgin). And she is the spiritual confidante of billions of people, no matter how isolated or forgotten.

Muslims as well as Christians consider her to be holy above all women, and her name “Maryam” appears more often in the Koran than “Mary” does in the Bible. In the New Testament Mary speaks only four times, beginning with the Annunciation, when, according to Luke’s Gospel, the angel Gabriel appears to her and says she will bear “the Son of the Most High.” Mary answers, “Here am I, the servant of the Lord.” Her only extended speech, also in Luke, is the lyrical Magnificat, uttered in early pregnancy: “My soul magnifies the Lord, and my spirit rejoices in God my Savior, for he has looked with favor on the lowliness of his servant. Surely, from now on all generations will call me blessed.” Indeed they have.

Yet clues about her life are elusive. Scholars of Mary must take what they can from Hebrew Scriptures, first-century Mediterranean texts, the New Testament, and archaeological digs.

The Bible says she lived in Nazareth when Romans had control over the Jewish territory. After Mary became pregnant, her betrothed, Joseph, a carpenter, considered quietly leaving her until an angel came to him in a dream and told him not to. The birth of Jesus is mentioned in just two Gospels, Luke and Matthew. Mark and John refer to Jesus’ mother several times.

The Evangelists were writing 40 to 65 years after Christ’s death and were not biographers, says Father Bertrand Buby, the author of a three-volume study, Mary of Galilee, and a distinguished member of the faculty in the International Marian Research Institute at the University of Dayton, in Ohio. “So don’t expect them to have all the elements about Mary. Her life is picked up from hearsay.”

Some of the latest Mary scholarship focuses on her as a Jewish mother. María Enriqueta García, in her sacred theology dissertation at the Marian Institute, explains that Mary brings us to Jesus, who is the light of the world, just as Jewish mothers light the Shabbat candles. “We see the relationship of Mary with us isn’t just any relationship—it’s sacred.”

During the first millennium, as Christianity became the official religion of the Roman Empire and began spreading into Europe, Mary typically was portrayed as an imperial figure, the equal of emperors, dressed in royal purple and gold. In the second millennium, beginning in the 12th century, says medieval historian Miri Rubin of Queen Mary University of London, “she underwent a dramatic shift,” evolving into a more accessible, kinder, gentler maternal figure. She served as a substitute mother in monasteries and convents, which novices often entered at a tender age. “A mother’s love,” Rubin says, “came to express the core of the religious story.”

Because so little is known of Mary from Scripture, “you can project on her whatever cultural values you have,” says Amy-Jill Levine, a professor of New Testament and Jewish studies at Vanderbilt University. “A cultural confection,” according to Rubin. Levine adds, “She can be the grieving mother, the young virgin, the goddess figure. Just as Jesus is the ideal man, Mary is the ideal woman.”

During the Reformation (1517-1648), the idea of Mary as intercessor fell out of favor with Protestants, who advocated going straight to God in prayer. But Mary gained millions of new Catholic followers with the Spanish conquest in the New World in the early 1500s—and, more recently, in Africa as Christianity has spread there.

Kibeho, a small town in southern Rwanda, is remembered as the place where the Virgin Mary appeared to three young girls and foretold of the blood and horror of the genocide that would traumatize the country in 1994, when the majority Hutu attacked the minority Tutsi and in three months more than 800,000 people were slaughtered.

In March 1982 the local bishop asked Venant Ntabomvura, a doctor, to go to a girls boarding school on a hillside in Kibeho. He was to investigate three students who had reported visions and conversations with the Virgin Mary. Ntabomvura, a kindly ear, nose, and throat specialist who, at 89, is still practicing, says Alphonsine Mumureke had first told of visits by apparitions the previous November. When they occurred, he says, “she was talking to someone exactly as if she were talking on the phone.”

Mary appeared first to Alphonsine, then to Anathalie Mukamazimpaka, followed by Marie Claire Mukangango. The girls said they spent countless hours in conversations with the Virgin, who called herself Nyina wa Jambo, Mother of the Word. Mary spoke to the girls so often that they called her Mama.

I found Anathalie at dusk one evening in her modest home near her old school, surrounded by rosaries and statues of the Virgin.

“The first time she appeared,” Anathalie said, “I was reciting the rosary, and she called me by my name. I heard her say, ‘Nathalie, my child.’ She looked very beautiful indeed, between 20 and 30 years old. She spoke in Kinyarwanda in a very calm and soft voice. She was in a blue veil and white dress. She never told me why she chose me. She said she appears to anyone she wants, anytime she wants, anywhere she wants.” She never mentioned any particular religion, Anathalie said. “She only asks us to love her as much as she loves us.”

Mary’s dire prophecy came on a day in 1982 everyone expected to be especially happy: August 15, the Feast of Mary’s Assumption into heaven. Ntabomvura was there, and Gaspard Garuka, who lived nearby. The girls were crying because, they reported, the Virgin was in tears too, Garuka says. He remembers that Alphonsine “fell down many times, because what she watched was very terrible. One time she even asked, ‘Please, hide this from my eyes.’”

Anathalie said that what Mary predicted “is exactly what I saw” during the genocide 12 years later. “People killing others using spears, burning fire, people’s skulls and heads cut off. I saw mass graves surrounded by so much darkness, blood running all over like rivers. All of this had been predicted.” Anathalie was able to flee Rwanda to the Democratic Republic of the Congo and then Kenya. Alphonsine became a monastic sister in Italy. Marie Claire was killed in the genocide. On June 29, 2001, nearly 20 years after Alphonsine had first reported her apparition, Rwanda’s Bishop Augustin Misago and the Vatican declared that, yes, the Virgin Mary had appeared at Kibeho.

Michael O’Neill, 39, a Stanford University graduate in mechanical engineering and product design, is the Virgin Mary’s big data numbers cruncher. On his website, MiracleHunter.com, he has codified every known apparition of Mary back to A.D. 40. Systematic investigation and documentation of supernatural occurrences began with the Council of Trent, the Catholic Church’s ecumenical reaction to the Reformation, more than 450 years ago. Of the 2,000 apparitions reported since then, Miracle Hunter cites a mere 28 as approved by local bishops, who are the first to decide whether “seers” seem plausible. Sixteen of those have been recognized by the Vatican.

O’Neill, in his newly published book, Exploring the Miraculous, details the Vatican’s painstaking process when deciding whether to endorse an apparition as miraculous—“truly extraordinary.” The “authenticity” and mental stability of the seer are prime, and anyone suspected of trying to gain fame or riches from contact with the Virgin Mary is ignored or condemned.

Medjugorje is one of some two dozen sites in wait-and-see mode for Vatican approval. The local bishops with authority over Medjugorje have never given credence to the apparitions and have been at odds with the Franciscan priests who run the parish and are staunch believers. To resolve the impasse, a Vatican commission was appointed. It concluded its work in 2014.

The Vatican would never approve an alleged apparition whose message contradicted church teachings, and the faithful aren’t required to believe in apparitions. Many, including priests, do not. “What is from Mary versus what is captured and interpreted by the seer is hard to distinguish,” says Father Johann Roten, director of research and special projects at the University of Dayton’s Marian Library, with more than a hundred thousand volumes on Mary. Ultimately the decision is based on faith.

“Miracles transcend physical nature and physical laws,” says Robert Spitzer, a Jesuit priest who heads the Magis Center in California, which according to its website is dedicated to explaining faith, physics, and philosophy. As Spitzer says, “Science looks for physical laws in nature, so you’re up against a paradox. Can you get a scientific test for miracles? No. Science will only test for physical laws or physical results.”

Nonetheless, over the years, as part of the church’s investigative process, seers have been subjected to batteries of tests. There have been attempts to get the visionaries in Medjugorje to blink or react to loud noises while they experience apparitions. In 2001 the peer-reviewed Journal of Scientific Exploration reported on the visionaries’ “partial and variable disconnection from the outside world at the time of the apparitional experience.” The extreme sound and light sensations traveled normally to their brains, but “the cerebral cortex does not perceive the transmission of the auditory and visual neuronal stimuli.” So far, science has no explanation.

In the medical profession what you and I might call a miracle is often referred to as “spontaneous remission” or “regression to mean.” Frank McGovern, the Boston urologic surgeon who had done all he could for Arthur Boyle, told me that the cancer’s virtual disappearance was a “rare” but statistically possible happening. But, he added, “I also believe there are times in human life when we are way beyond what we ever expect.”

Did the intense heat Boyle experienced when Vicka Ivankovic-Mijatovic held his head in her hand play a part in his healing? According to the 2006 book Hyperthermia in Cancer Treatment: A Primer, “Spontaneous regression of some cancers has been demonstrated to be associated [with] the induction of fever and activation of immunity.”

Boyle said that although he continued his tests after his return from Medjugorje, “it was faith that enabled me to get into a state of peace where my immune system rebooted itself and killed the cancer—that was all done through God.”

Certain images and stories of the Virgin Mary are so powerful they help define a country. That’s the case with Our Lady of Guadalupe, whose image on the tilma, or cloak, of a poor Indian man gave rise, in 1531, to Mexican identity. Anyone witnessing the outpouring of love and devotion that pilgrims demonstrate for their beloved Madre on the days leading up to the Feast of Our Lady of Guadalupe—broadcast live throughout the country on December 12—can see that the Virgin Mary is deeply embedded in Mexican hearts and souls.

Her image was what Mexicans carried into their war against Spain for independence in 1810 and their internal revolution in 1910. César Chávez marched with her banner in his fight to unionize farmworkers in California in the 1960s. Our Lady of Guadalupe conferred instant benediction on the once despised mestizo children of Spaniards and Indians. She is the symbol of la raza, the definition of what it means to be Mexican, and because of Our Lady of Guadalupe, Mexicans have always believed they’re special.

At dawn on December 11, the day before the Feast of Our Lady of Guadalupe, I drove southeast from Mexico City toward Puebla. Pilgrims were thronging in the opposite direction, toward the Basilica of Our Lady of Guadalupe, the great shrine in the heart of the capital. Along the busy highway I saw people walking alone or in groups, packs of cyclists dressed alike, and numerous pickups flying by with flashing colored lights, artificial flowers, and statues of the Virgin wobbling in the back.

I pulled off the highway at a camp in the woods where pilgrims sleep at night on the cold ground. Mariachi music blared from portable speakers near a small fire. A breakfast stand had been set up, with free coffee, tea, and pastries. A volunteer told me that leading up to the Feast of Guadalupe, they feed 5,000 pilgrims a day here.

“Mexico belongs to the Virgin, and the Virgin belongs to Mexico,” said volunteer Treno Garay as he ladled out coffee. Four generations of women from one family said they walk ten hours a day from the town of Papalotla, in the state of Tlaxcala, but spend nights in the family truck, driven by a male relative. A 77-year-old woman was making the trek from Santa María, in the state of Puebla, with her 19-year-old grandson. A truck driver who comes from California each year put it this way: “Everyone has to visit their mother.”

The next morning when I arrived at the plaza in front of the basilica, a steady stream of people of all ages—including Alejandra Anai Hernán de Romero, an 18-year-old mother clutching her sick seven-week-old baby, Dieguito, born with a kidney malfunction—were shuffling on their knees across the square, standing only when they entered the basilica. Many had tears streaming down their cheeks. Most I talked to said they were coming to give thanks: They had made a promise to the Virgin, and she had answered their prayer.

In the basilica, behind the main altar, protected by glass, hung the original cloth image of Our Lady of Guadalupe, focusing the rapt attention of the faithful passing by on a moving walkway. According to legend, accepted by the church, it was in 1531 that the Virgin of Guadalupe spoke, in Nahuatl (the Aztec language), to Juan Diego, a baptized Indian canonized in 2002. She urged him to tell the bishop that she wanted a church built on the site, Tepeyac Hill, which had been a place for worshipping Aztec earth goddesses.

Juan Diego didn’t have much luck with the bishop, who wanted a sign of some sort. Mary instructed him to climb the hill, cut some flowers, and present them to the bishop. Flowers don’t bloom there in December, but Juan Diego gathered a bouquet of beautiful roses, which he folded into his tilma, believed to be woven from agave fibers. When he finally got to see the bishop and opened his cloak, the roses spilled out, revealing the image of Our Lady of Guadalupe. This is the only time Mary is said to have left a painted portrait of herself.

Many art historians see this as a standard European depiction of Mary, typical of the 16th century. But within the past several decades some church scholars have begun to interpret the visual imagery to be a combination of Catholic and what they consider to be Aztec iconography. According to such recent interpretations, an illiterate Indian would instantly be able to read the symbols as a nonverbal catechism. The dusky woman’s dark hair is parted in the middle, possibly symbolizing that she’s a virgin, but she wears a black bow high around her waist, a sign that she’s pregnant. Around her neck is a brooch—not the green stone Aztec deities often displayed but a cross. Her downcast eyes show that she isn’t a goddess. Similarly, her hands, clasped in prayer, also communicate that she isn’t divine. One of her legs is bent, suggesting that she could be dancing in prayer. The turquoise of her cloak signifies divinity and sky to the Aztec. The glyph of a four-petaled flower in the center of her rose-colored tunic supposedly means that she is the god bearer.

Remarkably, the image hasn’t deteriorated, according to the church, even though the cloth hung in the basilica for more than a century without protection, vulnerable to dirt and smoke. “She’s imprinted like a photo,” says Nydia Mirna Rodríguez Alatorre, director of the basilica museum, who explains that in 1785 a worker cleaning the silver frame accidentally spilled nitric acid on the image. It remained intact. An affidavit from several decades later says that the spill left only a vague mark like a water stain. In 1921 Luciano Pérez Carpio, who worked in an office of Mexico’s president tasked with weakening the grip of religion, placed a bomb in a bouquet of flowers below the image. The blast destroyed the altar and bent its bronze crucifix and the candelabra nearby. The image of the Virgin was untouched.

“When the devotion to the Virgin of Guadalupe disappears,” Rodríguez Alatorre says, “the identity of Mexico will disappear.”

“Mary is the purest and most virtuous of all women in the universe,” says Bakr Zaki Awad, dean of the theology faculty at Al Azhar University, Cairo’s leading theological university.

In Egypt I talked with devout Muslims who, because of their reverence for the Virgin Mary, had no qualms about visiting Christian churches and praying to her in church as well as mosque. One day in Cairo I encountered two young Muslim women in head scarves standing in front of the old Coptic Abu Serga church, built over a cave that is said to have been used by the Holy Family. It was the eve of Coptic Easter, and inside, the congregants chanted and prayed for hours. Outside, the women said they loved Mary from studying her in the Koran.

“Her story tells us a lot of things,” Youra, 21, said. “She is able to face lots of hardships in her life because of her faith, her belief in God.” Youra’s friend, Aya, added, “There’s a sura in her name in the Koran, so we were curious what was going on inside the church.”

I met Nabila Badr, 53, at a Coptic church along the Nile in a part of Cairo called Al Adaweya—one of the many places in Egypt where the Holy Family is said to have stopped. Badr is a married mother of three and an events organizer for the governor of a state near Cairo. Along with her Koran, she carries Christian medals of the Virgin Mary in her purse. In a small room in the back of the church Badr mingled with Coptic Christians praying there, lit candle after candle, bowed, and prayed to an icon of Mary on the wall that was claimed to have once wept tears of oil. Badr said she talks to Mary about her life and that Mary has answered her several times by showing her visions in dreams that later came true.

Like many Egyptians, Badr also believes in jinn, or spirits, who influence life for good or bad, although she claims only to have her own angel. “He too believes in the Virgin Mary,” she said. Badr often asks Mary to intercede for her, and she composed a poem to Mary. “When I feel down,” Badr said, “I pray to God very much, but I also consult Mary, and after a while things calm down.”

At St. Mary’s church in Zaytun, a neighborhood in Old Cairo, apparitions of a silent Madonna bathed in white light are said to have appeared at night above the domes of the church for three years, from 1968 to 1971. Glowing white doves sometimes accompanied the apparitions. Yohanna Yassa, a Coptic priest who has ministered at St. Mary’s since 1964, told me that often Muslim women who want to get pregnant come to his church to pray. “Today we had a lady who came for a blessing,” he said. “Mary is calling us spiritually, and because of that, both Muslims and Christians love her and respect her.”

Following the many paths of Mary, I learned that she has often appeared to people in crisis zones, such as Kibeho and Bosnia and Herzegovina, seeking to warn of danger or to serve as a symbol of healing. In her aftermath come physical cures said to be miraculous, as at Medjugorje, and spiritual healings too numerous to count. Lourdes, the Virgin’s most famous pilgrimage site, at the foot of the Pyrenees in southwestern France, is her miracle factory, with more than 7,000 miraculous cures claimed since the mid-1800s. Only 69 have been officially recognized by church authorities.

Everything at Lourdes is about scale: more than a hundred acres, six million visitors a year, space for 25,000 worshippers in the giant underground basilica. It was built in 1958 to commemorate the centennial of the Virgin Mary’s first appearance, in 1858, to Bernadette, an illiterate 14-year-old peasant girl. (St. Bernadette was canonized on December 8, 1933.) The nearby Grotto of Our Lady of Lourdes, its stones worn by millions of feet, is where the Virgin is said to have commanded Bernadette to scoop up the mud with her hands to make a spring gurgle from the damp soil. That miraculous water is the source for baths that attract thousands daily in wheelchairs, and thousands more on foot, to pray for cures. Volunteers push les malades, the sick, in blue buggies in endless, snaking lines along Lourdes’s narrow streets, flanked by dozens of religious curio shops.

The day I visited the baths, it was pouring rain, and cold. There’s a strict protocol for how you disrobe and then tie a light linen cloth around your body for a quick, private dip, supported under each arm by a volunteer. “Say your intention, make the sign of the cross, and we’ll escort you down,” a kindly Irish woman told me. Then came the freezing immersion—a bracing moment of deep peace.

Shortly after World War II, members of the French and German militaries met at Lourdes to reconcile and heal the wounds of war; now every spring veterans groups are among the hordes of pilgrims. On May 14, 2015, I joined 184 wounded warriors—U.S. combat veterans who had served in Iraq and Afghanistan—and their families, sponsored by the Archdiocese for the Military Services and the Knights of Columbus. They had come for the annual pilgrimage of militaries (from 35 nations this year) to celebrate peace. For the rest of their lives, all these quietly brave men and women and those who support them must contend with debilitating injuries suffered sometimes during multiple deployments.

Perkins grew up a poor white girl in a mostly black, inner-city neighborhood in Tacoma, Washington, with nominal support from her mother and alcoholic stepfather. At age ten, she was sent to pick berries in the fields. She learned German during a gap year between high school and college when she lived as an “indentured servant,” cleaning rooms in a family-owned hotel in the Bavarian Alps. Her only recreation was to hike the mountain trails, where she encountered little shrines to Mary.

Perkins attended the University of San Francisco, a Jesuit school, for 12 years but left a few credits short and graduated from SUNY, Albany. While in San Francisco, she took a job at Macy’s, working her way up the corporate ladder to become a senior executive. In college she also joined the Army Reserve. After marrying a Green Beret, she signed up with the Army full-time and worked in counterintelligence.

For Perkins, “Lourdes really forces each person to look at herself spiritually. Everything is always rushing by so fast. We’re overwhelmed by media and caught up in the day-to-day. People don’t force themselves to look at what’s most important—the integrity of the soul.”

During the closing ceremonies at a giant Mass in the basilica, one of the European bishops, preaching in French, said, “World War III is already under way in the Middle East and Africa.” He praised the military there for focusing “on peace, justice, and human rights. May this experience make you witnesses for hope.”

I thought of the indelible scene of the candlelight procession the night before—thousands of pilgrims, from places ranging from Argentina to Zambia, silently lifting their candles in prayer. It had ended with dozens of veterans in wheelchairs lining up in front, next to the Grotto of Our Lady of Lourdes, for songs and prayers. So many souls yearning to be witnesses for hope, so many souls imbued with the belief that the Virgin Mary was lighting their way.