A Soviet agent used five aliases to move spies through the world's ports for decades; the British kept the record of his movements in a file that identifies the holes in Western security.
While Paris burned with sabotage, Madrid served as a vetting ground where a secretive counter-intelligence unit erased operations without explanation, a process kept secret for decades.
Spies in the Red Cross and leaks that risked firing squads for operators stayed hidden in records the US government previously withheld, including files on chemical warfare in Europe.