As the peerlessly powerful and widely feared director of the Federal Bureau of Investigation over the course of almost five decades, J. Edgar Hoover saw himself in a constant state of war—against radicals, gangsters, Communists and any politicians, including presidents, who tried to get in his way. "J. Edgar," with Leonardo DiCaprio in the title role, is at war with itself, and everyone loses. Clint Eastwood's investigation of Hoover's life and tumultuous times seeks the cold facts behind the crime-fighter myths, the flesh-and-blood man behind the dour demeanor and the rumors of homosexuality. Yet Mr. Eastwood's ponderous direction, a clumsy script by Dustin Lance Black and ghastly slatherings of old-age makeup all conspire to put the story at an emotional and historical distance. It's a partially animated waxworks.

The production's internal conflict goes beyond style. "J. Edgar" is unsparing in its portrait of Hoover as a ruthless, self-dramatizing and sometimes delusional zealot—his loathing of Martin Luther King Jr. and John F. Kennedy, among others, is given special prominence—as well as a patriot, by his own lights, and a proponent of modern criminal science. Mr. DiCaprio's approach is equally unsparing; the actor declines to spare himself. His Hoover is more to be censured than pitied, an obsessive-compulsive creep with the vocal rhythms of a ball-peen hammer and a gimlet-eyed gift for blackmail.

At the very same time, the movie offers a love story in which the hero struggles with his sexuality, and with his supposedly closeted love—if there was a closet it stayed tightly shut, so most of the script's sexual content is conjecture—for Clyde Tolson, the FBI agent who came to be known as Hoover's constant companion. He's played by Armie Hammer, who, exempt from the cartoonish constraints of Mr. DiCaprio's role, manages to make Tolson appealing and fitfully interesting.

In principle, biography should do what "J. Edgar" tries to do—reveal an inner life, whether or not the subject is outwardly appealing. There's a certain logic to Mr. Black's having done the screenplay; he won an Oscar for writing "Milk," in which Sean Penn portrayed the gay activist Harvey Milk. This time, though, his script, along with stodgy staging and Tom Stern's cheerless cinematography, yields scenes that cross the line from awkward to embarrassing—not because the lovers are gay, or getting to be long in the tooth, but because they're written and observed as mawkish relics, rather than passionate individuals who speak and behave in the idioms of their day. (In a scene that may be the movie's nadir, Clyde's face falls, while his lips literally quiver, when Edgar reveals that he's been to dinner several times with Dorothy Lamour, that they've "become physical," and that it may finally be time for a Mrs. Hoover.)

Although "J. Edgar" spares us the spectacle of a make-believe Lamour, it's studded with other vignettes and dubious representations of historical figures: a charm-free Ginger Rogers, a blank-slate Charles Lindbergh, a cloddish Robert F. Kennedy and an appallingly crude approximation of Richard Nixon. Perhaps the saddest spectacle, representing the worst waste of talent, is Naomi Watts as Helen Gandy, Hoover's endlessly loyal private secretary. Ms. Watts is stuck with an opaque character, dreadful dialogue and, during the many sequences set in the twilight of Hoover's career, the sort of age makeup that should never deface as lovely a face as hers. Judi Dench fares slightly better as Annie Hoover, Edgar's mother. Annie may be a fire-breathing religious nut job, but at least the actress gets some fire to breathe.

Legendary power and its abuse always hold the potential for powerful drama; the trick is in the telling. This latest attempt to tell Hoover's story doesn't lack for ambition, only for expertise. Even if the personal side had been sharper and livelier, the historical side—partly satirical and partly objective—would have been ill-conceived. (Much of Hoover's career is explicated, tediously, through the device of him dictating salient details to an FBI biographer, and shown, confusingly, through the cracked prism of his self-inventions.) The script abounds in casual anachronisms—phrases like "fashion forward" and "a P.R. disaster"—and jumps back and forth in time without getting the feel of any period quite right. Fingerprints figured significantly in the bureau's evolution; at first Hoover called them finger patterns, or finger imprints. Whatever you want to call the ones that besmudge "J. Edgar," they're evidence of heavy hands.