Charles Lenox, once London's leading private investigator, has just given up his seat in Parliament to return to his first love, detection. He and three colleagues start a new detective agency, but as the months pass, Lenox begins to question whether he can still do the job. Then a friend, a member of Scotland Yard, is shot near Regent's Park. As Lenox begins to parse the peculiar details of the death, he realizes that the incident may lead him into grave personal danger, and a terrible truth.