When they spotted it, there was no mistaking what they were looking at: a boot melting out of the ice. As they drew closer, they could tell the cracked leather was old and worn, and the sole was studded and bracketed with the diamond-patterned steel hobnails of a bygone era of climbing.
In September, on the broad expanse of the Central Rongbuk Glacier, below the north face of Mount Everest, a National Geographic documentary team that included the photographer and director Jimmy Chin, along with filmmakers and climbers Erich Roepke and Mark Fisher, examined the boot more closely. Inside, they discovered a foot, remains that they instantly recognized as belonging to Andrew Comyn Irvine, or Sandy, as he was known, who vanished 100 years ago with the famed climber George Mallory.