Roswell: First Witness series follows the grandchildren of Major Jesse A Marcel, the first person on the scene of the Roswell crash in July 1947. His family believe Major Marcel was pressured by the US government to retract his original statement of what he discovered at the crash site and deny he ever saw evidence of a UFO. They possess Marcel's diary, believed to contain clues about the truth of what happened at Roswell and new evidence of where the alien wreckage might still lie buried. The investigation is led by Ben Smith, a former CIA operative.