Fifty tourists a year get lost in Joshua Tree National Park and find their way back out. In 2010, 66-year-old Bill Ewasko went in and never came out. For The New York Times Magazine, Geoff Manaugh follows the eight-year search for Ewasko and the men who obsessed about finding him.

Search-and-rescue experts have developed lost-person-behavior algorithms to track missing hikers. They use cellphone pings to create a map and timeline, and use past behavior to try to guess their target’s behavior. Technology has also turned amateurs into sleuths and spun web forums devoted to missing people. We live in what Manaugh calls “a golden age for amateur investigations.” For some, missing persons cases become a hobby, a puzzle to solve, a form of salvation, even when wilderness areas thwart their techniques.

To hear Marsland tell it, his inaugural trip to the park, on March 1, 2013, bore the full force of revelation. He purchased hiking gear at a Los Angeles outdoors store, booked himself a room at a nearby hotel in Yucca Valley and set off at 6:30 a.m. He managed to get much farther into the park than he expected. But rather than retreat, he pushed on, walking up the side of Smith Water Canyon. At the top of the ridgeline, he found a curious pit. “It was enclosed by rocks, and you couldn’t really see it from the side,” Marsland told me. “I remember thinking that this is exactly the kind of place where you would expect Bill to be: someplace where he had fallen down, he couldn’t get out and you would never find him. I remember thinking that I had to clear this pit. I had to crawl right up to the edge of it and look down, and I remember being so afraid that I would fall into the pit myself.”

The pit contained no bodies, or even clues, but that moment of possibility was everything. Marsland began drinking less, losing nearly 40 pounds as he reoriented his free time around this quest to find a stranger. “I crossed the line from being somebody who just sat in his room and passively participated in something to being actively involved,” he said. “It was a big moment for me, and it led to a lot of other good things happening in my life.”

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