In 1938, according to accounts that have been repeated, contested, and re-repeated for nearly a century, a team of researchers entered a system of caves in the Himalayas near the border between Tibet and China. What they reportedly found inside those caves has never been produced for independent examination. It has never been carbon-dated by an accredited laboratory. It has never been photographed in conditions that satisfy modern forensic standards. And yet, the description of what they found has persisted in the public record with a tenacity that no ordinary hoax achieves.