In the year 2000, someone calling themselves John Titor appeared on internet forums claiming to be a soldier from 2036 sent back to retrieve an IBM 5100 computer. For five months, he posted detailed descriptions of time travel mechanics, future events, and even uploaded technical diagrams of his time machine before disappearing without a trace. We unravel every thread of the most compelling time traveler story ever told—and investigate whether it might actually be true.