Fei Nong, a senior official of the British Foreign Office, was informed by an anonymous letter that he was a spy. Investigator Charles was ordered to interview him, but Fei Nong committed suicide. Charles found from various signs that Vernon did not commit suicide, so he launched a personal investigation. With the help of a shrewd old criminal policeman, she lured out the true face of Mrs. Fernon and was surprised to find that there were still a pair of dark hands behind the scenes manipulating her husband's state secrets.