The morning before Dean Potter died, in May, 2015, he and his girlfriend, Jennifer Rapp, were puttering around their house in Yosemite. Potter, the world-famous rock climber and daredevil, had just returned from a trip to Germany, and Rapp had flown in from Vancouver, the headquarters of the apparel company Arc’teryx, where she was head of communications. In the living room, Rapp tried on some dresses for Potter. “Help me pick one,” she said.