Alexander Feklisov, a master spy from the Soviet Union, was assigned to New York in the 1940s. Here, he met Julius Rosenberg and had over 50 secret meetings with him, receiving an impressive amount of classified scientific and technological information, which was passed on to the USSR. He and Rosenberg built a wide network of agents in the US. Any doubts since the trial and execution of Julius and Ethel Rosenberg have now become impossible to deny. Later, in London in the 1950s, Feklisov was given vitally important nuclear secrets of the H-bomb. In the 1960s, the author played a crucial role in the Cuban Missile Crisis, which brought the world to the brink of nuclear war. Alexander Feklisov is the last and most important witness.