Born in Brooklyn, New York in 1922. Daughter of a prominent to manufacturer.

Graduated Cum Laude from Barnhard College in 1943, having focused on Russian History and Culture. Employed by the United States Department of Justice, first in New York and later in Washington D.C. after being promoted to the foreign agents registration division. Had access to FBI documents with lists of foreign diplomats and suspected foreign spies.Was highly praised for her analysis on Soviet political and cultural issues. Received promotions.

Began supplying information to the Soviets sometime between 1945 and 1947. Was assigned a special Soviet contact, an Intelligence Officer named Valentin Gubitchev. Gubitchev was a former member of the Soviet delegation to the United Nations. At the time he began meeting with Coplon, he was an employee for the United Nations.

In 1948, an unidentified informant passed information along to the Director of the Federal Bureau of Investigation J. Edgar Hoover, reporting that a woman, formerly employed in the New York branch but then working at the Washington offices of the Department of Justices was passing secrets that were making their way to the Russian Embassy in New York.

Was placed under intense surveillance. FBI agents placed taps on her telephone line, monitored her mail and followed her as she traveled. Neighbors claimed that Coplon was quiet and did not entertain male guest in her apartment. Surveillance, however, indicated that she engaged in sexual affairs with several men, presumably for the purpose of obtaining classified information.

Often traveled to New York City on the weekends, often asking to leave from work early on Fridays. Took classified documents home with her and retyped them. Gave the retyped documents to Gubitchev when she visited him in New York.

Requested a special document containing a list of suspected Soviet spies. Director Hoover personally delivered a fake version of the document to Coplon’s supervisor, who immediately provided it to her. Coplon, upon receiving the document requested the rest of the day off and then traveled to New York for the weekend (followed by FBI agents – January 14, 1949).

Was trailed by FBI agents around Manhattan until she finally met with Gubitchen in a restaurant. After exchanging documents, the couple left and boarded a subway train. As the doors to the train were closing, Gubitchev bolted from the train and evaded the trailing FBI agents.

Having been observed passing documents, Coplon was transferred to another division of the Department of Justice, in order to keep her away from sensitive documents. Coplon continued to seek access to such documents, volunteering to aid her replacement in getting up to speed.

Requested additional classified information that her supervisor had recently obtained (fake information received from Hoover). Her supervisor left the information in Coplon’s view and left the room. Coplon left the room and caught a train to New York (March 6, 1949).

After meeting Gubitchev, Coplon and her Soviet handler were confronted by FBI agents. After trying to flee, both were apprehended and arrested. Coplon had numerous top-secret documents on her person, including the one provided by Hoover. Coplon was charged with treason and espionage and Gubitchev was charged with espionage.

Coplon faced two trials, one in Washington and one in New York. She was convicted in both. Gubitchev was convicted and deported. Coplon convictions were overturned, as an Appeals Court ruled that the FBI had illegally recorded conversations between Coplon and her attorney and further that the FBI had arrested her without an arrest warrant.

Coplon married one of her attorneys and moved to New York where she settled down as a housewife.