On New Year's Day in 1985, Eastern Air Lines Flight 980 was carrying 29 passengers and a hell of a lot of contraband when it crashed into the side of a 21,112-foot mountain in Bolivia. For decades conspiracy theories abounded as the wreckage remained inaccessible, the bodies unrecovered, the black box missing. Then two friends from Boston organized an expedition that would blow the case wide open. ... Mount Illimani, a 21,122-foot mass of rocks and glaciers rising from the eastern edge of Bolivia’s Altiplano region, towers over La Paz. The Andean mountain is so textured by ridgelines, high peaks, and shadows that, viewed from the city, it seems to move and change shape throughout the day. ... In all, at least five expeditions have climbed Illimani in search of the wreckage over the past 30 years. None of them found any bodies or flight recorders, nor could anybody establish what brought down the plane. Officially, it was designated a “controlled flight into terrain,” which means it couldn’t be blamed on a bird strike or an engine malfunction or hijackers. The NTSB ultimately filed its own report to supplement the Bolivian one, but it came to the same flat conclusion: the plane was destroyed because it ran into a mountain. ... As time passed, however, details emerged that invited speculation among South American journalists, the families of the victims, and anyone else still following the story. ... Where were the flight recorders? Where were the bodies? ... So here’s another question worth asking: What sort of foolhardy seeker suddenly takes an interest in a 30-year-old plane crash?