Actor Richard Kiley narrates this investigation into both new and well-known clues to the origins of the human race. Razor -sharp tools of our ancestors are examined and discussed by historians and experts. A number of fossilized skeletons that are more than a million years old are examined by scientists. Ash-entombed footprints provide a trail into centuries that ended long ago. Viewers will see many artifacts that all relate to what is often referred to as one of the "greatest mysteries of all time."