Ancient Aliens: Special Presentation

Gone without a Trace (1x10)

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Tens of thousands of individuals go missing every year and many are never found. But this is not a new phenomenon. Throughout history, ships and planes have mysteriously vanished mid-journey--and entire civilizations, communities, and tribes have seemingly disappeared from the face of the Earth without a trace. Might there be a connection between all these missing person cases--one possibly involving otherworldly portals and even extraterrestrial beings?