This is the final article in a three-part investigation of what may have been a savage crime or a tragic accident. In addition to a trove of documents and photographs revealing hitherto unexamined aspects of the case, The Daily Beast also consulted several top sleuths in fields as varied as wilderness survival and photographic analysis, including forensic anthropologist and best-selling author Kathy Reichs.

BOQUETE, Panama—At the crest of the Continental Divide stands a rustproof sign that reads:

END OF TRAIL, NO RETURN PASSAGE