Thomas Branch McAdams, 67, of Portland, Oregon, was last seen Saturday, September 24, 2016, and is believed to have headed out for a day hike in the Columbia River Gorge. A retired burn nurse who left the Oregon Burn Center in January 2016 after 38 years, McAdams was an experienced hiker who regularly used Gorge trails and is described as an active, outdoorsy family man who was married with two daughters.

It was uncharacteristic when he failed to return that evening; he left his usual hiking gear at home and was reported missing on Monday, September 26. His vehicle was found at the Horsetail Falls trailhead. Search and rescue mounted an extensive response — up to 150 people covered more than 200 miles of trails, with canine teams and aircraft. A plane picked up a credible hit near the Nesmith Trail area, but a ground search there found no sign of McAdams. The official search was suspended a few days later pending new leads, and no trace of him or his belongings has been found since.

What information might help explain how an experienced hiker vanished from familiar terrain?