Jean-Sébastien Beaud didn't know what he'd find when he descended, by a rope dangling from a helicopter, onto a steep mountainside in the French Alps. Twenty minutes earlier, Beaud and three colleagues from the mountain rescue squad of the gendarmerie had received a call from an air-traffic control center in Lyon, telling them that a plane had disappeared from the radar screen over the Massif des Trois-Évêchés, a range of 9,000-foot peaks northwest of Nice. Now, at 11:10 A.M. on Tuesday, March 24, 2015, Beaud was lowered from the four-seat chopper and set down gently on the rock face. Plumes of smoke and small flames rose from debris scattered across the slope, and the odor of jet fuel thickened the air around him. A tall and athletic man in his early thirties, with a faint mustache and goatee, Beaud moved cautiously down the field of black scree, making a mental inventory of what he saw: a human torso, shoes, suitcases, seats, bits of fuselage, and everywhere, detached hands and feet. He could tell immediately that an aircraft had smashed full speed into the mountain and been obliterated. Rattled but focused on the task at hand, he clicked on his radio and notified headquarters: There could not possibly be any survivors.