SPIES BENEATH BERLIN tells the extraordinary true story of the top-secret mission to build a spy tunnel into the Soviet sector of one of the most heavily guarded cities in history. CIA Chief Alan Dulles would later describe the tunnel as "one of the most valuable and daring operations ever undertaken." Drawing upon gripping personal accounts combined with fresh scientific and historical analysis, this film pieces together the full story of a remarkable mission. The program's historical consultant is David Staffer - author of "Spies Beneath Berlin."