Paying homage to film noir of a bygone Hollywood era through its low-light aesthetic and dramatic voiceovers, Clint Eastwood’s ambitious biopic “J. Edgar” is a complex character study of the notorious founding director of the Federal Bureau of Investigation. Starring Leonardo DiCaprio as J. Edgar Hoover, the film recounts both his achievements and abuses, interspersed with glimpses of a little-known personal life, in order to form a meditation on that grey area between morality, justice and power.

In 1919, a 24-year-old Hoover (DiCaprio) living in Washington, D.C., is inspired to join the Department of Justice after witnessing the incompetence of the investigators at the scene of a terrorist bombing. Ambitious, smart and socially awkward, Hoover quickly rises through the ranks to become the FBI’s founding director–a position he would hold for the next 37 years until his death. Loosely framed by an elderly Hoover dictating the history of the institution to a younger agent, the story of “J. Edgar” unfolds like a web, constantly jumping back and forth across his long tenure but always linked by DiCaprio’s booming, authoritarian voice.

Early in his career Hoover champions the widespread practice of fingerprinting, and under his leadership the bureau transforms from a nominal threat lacking proper jurisdiction to a political powerhouse. But with time his actions are marked by a constantly intensifying determination bordering upon lunacy, leading him to tap President Kennedy’s phones, attempt to blackmail Martin Luther King Jr. out of accepting the Nobel Prize and even manipulate the careers of his own agents when they threaten to outshine him. Hoover’s personal life is equally controversial, with the film paying particular attention to his ever-evolving relationships with his straight-laced mother Annie (Judi Dench), devoted personal secretary Helen Gandy (Naomi Watts) and close colleague Clyde Tolson (Armie Hammer). Thus, bit by bit, Hoover’s many facets gradually come into focus.

DiCaprio commands the screen as the unflappable and unscrupulous pioneer, even under varying layers of prosthetic makeup, which, for the record, is the most convincing use this reviewer has witnessed to date. While his rendition of Hoover’s distinct diction may seem jarring and forced in voiceover, it thankfully flows more naturally as scenes play out. As Tolson–Hoover’s second in command, best friend and, according to rumors, gay lover–Hammer provides a decent foil. But if there is a supporting actor nomination to be earned, it likely belongs to Watts, whose subtle performance as Gandy is more affecting.

It would be easy to attribute Hoover’s more distasteful actions to the old adage “absolute power corrupts absolutely,” but in this case the situation is not clear-cut. Thoroughly engrossing and more thoughtfully crafted than most biopics, “J. Edgar” merely provides hints and suggestions regarding its subject while leaving the viewer to piece together the final portrait.