After Thomas' sister Charlotte, drowns in an accident while swimming, he goes through her estate and among her papers, discovers evidence of their father’s activities in the secret service. It appears that Charlotte was trying to find out more about this and her death may be connected to their deceased father's work. Thomas arranges a meeting with an old navy comrade of his father’s, who evades his questions. Thomas is fairly certain he is not telling him the truth; moreover he feels certain the man must have met with his sister shortly before her death. As Thomas embarks on an investigation he soon finds himself and his family under surveillance by an unknown group of people.