Edgar Hoover (Leonardo DiCaprio), the director of the FBI in his seventies, was invited by "Crime Documentary" to dictate his personal memoirs. Hoover told the ghostwriter of his memoirs about his important life journey since 1919: arresting left-wing leaders, arresting notorious gang leaders, and cracking the Lindbergh kidnapping case that shocked the United States. According to Hoover's account, he overcame all objections, reorganized the FBI, introduced high-tech investigative methods, and worked hard for the peace and stability of American society. On the other hand, his private life became the part he wanted to cover up. Just as Hoover was looking back on his life, there were still many turbulent factors in American society. Clyde Tolson (Armie Hammer), Hoover's personal assistant for many years, also seemed to have an unusual relationship with him...