Attractive and talented, Maria Knuth was an actress without work following World War II because the German film industry was in shambles. In 1948 she befriended Heinko Kunze, a former Prussian officer and art historian who operated an antique shop in Berlin. Kunze loaned money to Knuth and slowly worked on her to join a group of Soviet spies who included Kunze, his mistress Luise Frankenberg, and one-time Polish cavalry officer Colonel Gregor Kowalski. This network was known as the Kolberg Ring, and busied itself with recruiting displaced East Germans into their ranks.
Knuth proved herself an excellent agent. She lured American and British officers into the Berlin antique shop, compromised them and extracted important information that she dutifully passed on to spymaster Kowalski. She became so successful that she was provided with more funds, and she was able to buy a handsome villa outside of Cologne. This was used as a love nest where more Allied officers and West German officials were compromised and bilked for information.
Knuth was promoted and ordered to take over the Frankfurt operation, which she did, proving herself to be one of the best Soviet spies in the West. In 1950 she was ordered to penetrate the newly established Amt Blank, a West German intelligence network organized to identify Soviet spies in the West. Knuth went to Amt offices and applied for a secretarial job, but was turned down because she did not know shorthand. Knuth later came to the attention of West German spymaster Reinhard Gehlen, who set out to trap Knuth.
In 1952, a "Dr. Petersen," claiming to be a West German agent opposed to German rearmament, was introduced to Knuth, and he offered to work for the Kolberg Ring. Although she was warned that Petersen might be a Gehlen agent, Knuth accepted him as a genuine, especially when she learned that he worked in the offices of West German Chancellor Konrad Adenauer. In fact, Knuth was so enamored with Petersen that she became his lover.
Petersen dutifully supplied Knuth with high-grade information, which she passed on to Kowalski and the Soviets. All of the information, however, was counterfeit intelligence concocted by Gehlen, who had planted Petersen. by 1953 Petersen had learned everything there was to know about Knuth and the Kolberg Ring. West German police rounded up all of its members including Knuth, who was caught collecting coded letters from Kowalski in a Cologne post office.
Kowalski escaped into East Germany, but his network was smalled. All of his agents, including Knuth, were quickly convicted and sent to prison. Knuth did not survive for long, though. By the time she was arrested she had already contracted cancer. She died in prison from the disease in 1954.