Berlin, in August 1961. On an S-Bahn train heading to Wannsee, a shot man is discovered, apparently an American. Shortly thereafter, another dead body is found, this time at a junkyard near Tempelhof Airport. Chief Inspector Tom Sydow quickly realizes that there is a connection between the two cases. But that's not all: Sydow uncovers an incredible conspiracy that seems to reach all the way to the CIA headquarters. Apparently, someone has managed to unveil the best-kept secret of the GDR: the plans for the construction of the Berlin Wall.