Who was CYNTHIA?

CYNTHIA was an American agent who had been recruited by the BSC. Married to British diplomat Arthur Pack, they were stationed in Warsaw. She formed liaisons with members of Poland's Foreign Service and was able to obtain information about the Heydrich Enigma. After Warsaw, the Packs were assigned to Chile and in 1940, CYNTHIA was sent to New York and then to Washington DC. She resumed an affair with an old lover, Admiral Alberto Lais and obtained the Italian naval ciphers. One day a Mr. Williams appeared at her apartment, and she realized that he was Bill Stevenson. He needed her to obtain certain correspondence between the Vichy French and Europe. She began the assignment in May 1941.