The Man From 2036. John Titor, the IBM 5100 and the Internet's Greatest Unsolved Mystery

On November 2, 2000, someone logged onto a small internet forum and described, in technical detail, a machine that could move a human being through time. Over four months and 151 posts he called himself John Titor, a soldier from 2036 sent back to retrieve a 1975 IBM 5100 with a hidden function almost nobody knew existed. Then he typed one last sentence and vanished. Four years later, an IBM engineer confirmed the hidden function was real.