As head of the FBI for nearly 50 years, J. Edgar Hoover (Leonardo DiCaprio) becomes one of America's most-powerful men. Serving through eight presidents and three wars, Hoover utilizes methods both ruthless and heroic to keep his country safe. Projecting a guarded persona in public and in private, he lets few into his inner circle. Among those closest to him are his protege and constant companion, Clyde Tolson (Armie Hammer), and Helen Gandy (Naomi Watts), his loyal secretary.