overview : Mysterious events, compelling figures and great unanswered questions from the past are explored, with a focus on the reclusive billionaire Howard Hughes; the CIA's top-secret experiments; the Unabomber and; little known stories from NASA's Apollo missions.

First Air Date : Jan 01, 1970

Last Air Date : Jan 25, 2011

Runtime : 45m

Episodes : 27

Seasons : 4

Genre : Documentary,

Companies : National Geographic

Countries : US

Keywords : investigation