He has been let into the secret: he has been cheated at gaming or horse-racing. He or she is in the grand secret, i.e. dead.
·vt To keep secret. II. Secret ·adj Separate; distinct. III. Secret ·adj A thing not discovered; w...
Webster's Dictionary of the English Language
·add. ·- The detective service of a government. In the United States, in time of peace the bureau of...