Jonathan Spollen, a 28-year-old Irishman with long brown hair and a delicate brogue, was at a crossroads in his life. He'd embarked on a career as an overseas journalist, working first as a reporter at the Daily Star Egypt in Cairo and then as a foreign editor at The National in Abu Dhabi. But now he was a copy editor for the International Herald Tribune in Hong Kong, approaching 30, and wondering if he liked where his life was going. In October 2011, following a split with his girlfriend, he bought some trekking gear, sent his laptop home to Dublin, and booked a flight to Kathmandu, Nepal. From there, Spollen made his way to India. He had visited before, spending time with an octogenarian yogi named Prahlad Jani—who claims his mastery of the ancient arts has allowed him to live without food for 70 years—and had come away entranced with the country. This time, Spollen roamed the subcontinent for several months, visiting the holy city of Varanasi, India's oldest inhabited settlement. In early February, Spollen called his mother, Lynda, to tell her he planned to spend two or three weeks hiking in the Himalayas near the pilgrimage site of Rishikesh, the yogaphilic city on the Ganges where the Beatles visited Maharishi Mahesh Yogi. She reportedly asked him not to go alone, but he told her that was the whole point. "It's a spiritual thing," he explained.

He was never heard from again.

A little over three weeks after that conversation, his parents were worried enough to post to IndiaMike.com, a forum for Western travelers to the subcontinent. Their message contained a picture of Spollen, the details of his last known sighting, and a plea: "Please, all of you, keep in regular contact with your families. Even if they don't say it, they care for you and worry about you!" A few days later, Spollen's father, David, flew to Rishikesh to organize a search party. In mid-March, local authorities found Spollen's passport, rucksack, bedroll, and cash beside a waterfall near the village of Patna, a few miles outside Rishikesh. From there, however, the trail went cold. Members of the IndiaMike community circulated missing-person posters that travelers hung along the Banana Pancake trail, a network of backpacker routes that stretches from Goa to Hanoi, but there were no new leads.

Today, the thread on Spollen's parents' initial post has grown to more than 1,700 responses. Some commenters believe he's dead, while others have speculated that he chose to renounce his previous life and is still living in the mountains somewhere, alone or with some cloistered sect. Many presume that whatever happened to him, his "spiritual thing" is responsible. They've seen it before: Some remember Ryan Chambers, a 21-year-old Australian spiritual seeker who visited ashrams before vanishing from Rishikesh in 2005, leaving his passport, wallet, and cell phone behind in his hotel room, along with a note that read, "If I'm gone, don't worry. I'm not dead, I'm freeing minds. But first I have to free my own." Other pilgrims have been taken in by false gurus who lure them with sham spirituality, then drain their bank accounts and sometimes imprison them; in March, just weeks after Spollen's disappearance, Nepalese police freed a 35-year-old Slovakian woman who'd reportedly been held captive for two months by the followers of a man claiming to be the reincarnated Buddha. Neeru Garg, the district police chief of the nearby city of Dehradun, says of his ongoing investigation into Spollen's disappearance, "We are concentrating on the ashrams and holy men in the area."

Stories like Spollen's feel like Eastern versions of Into the Wild, the 1996 book about a young adventurer who died after trying to live off the land in Alaska: They're tales of willful idealists whose romantic notions of remote lands lead them to embark on quixotic journeys. In April 2010, Spollen wrote a travel story for The National, about spending time with a peasant family in Kashmir, that supports that interpretation: "The simplest things became fascinating," he wrote. "I found myself becoming enthralled in their lives. And strangely, I felt part of it all." The region's spiritual underpinnings appear to have factored into its appeal for Spollen. "He did have a strong interest in spirituality," a college friend remarked on IndiaMike. "It doesn't explain . . . why he's been incommunicado, but it could be an indication that people are searching along the right lines." Although Spollen's parents have stopped commenting on his disappearance, his father told an Irish newspaper in late April that visiting India was an eye-opening experience. "I have, at times, thought I was looking at somebody completely different to the son that I knew," he said. "To suddenly discover that there may be a whole spiritual aspect to his life that we hadn't really touched on is astonishing."

Of course, Spollen is not here to describe the role that devotion played in his disappearance. But he fits the profile of the fervent young enthusiast of yoga, meditation, and Eastern thought who becomes lost—or worse—on a journey of spiritual self-discovery.

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India today is a burgeoning global superpower, a place of outrageous poverty, and a land of tech-support call centers. But many still think of it primarily as the birthplace of yoga and meditation. Westerners have been exploring Indian spirituality since the late 19th century, but they started traveling to the country in large numbers after the Beatles visited Rishikesh in 1968 to study under the maharishi. In 2010, nearly 5.8 million people, including about 930,000 Americans, traveled to India. Roughly a quarter of those who visit the state of Uttarakhand, where Rishikesh is located, go for spiritual reasons—to attend a meditation seminar or go on a religious pilgrimage.

Some are drawn by accounts of the powers of dedicated practitioners—yogis who can levitate, breathe for months while entombed underground, melt giant swaths of snow with their body heat—believing that they too will be able to accomplish extraordinary things. This quest to become superhuman—along with culture shock, emotional isolation, illicit drugs, and the physical toll of hard-core meditation—can cause Western seekers to lose their bearings. Seemingly sane people get out of bed one day claiming they've discovered the lost continent of Lemuria, or that the end of the world is nigh, or that they've awakened their third eye. Most recover, but some become permanently delusional. A few vanish or even turn up dead.